Topographical anatomy and operative surgery 3rd ed. / Цигикало О. В.

Fig. 2-32 Facial Muscles.

Fig. 2-33 Trigeminal Nerve (CN V) leaving the Skull.

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thetic agent at the infraorbital foramen or in the infraorbital canal (e.g., for treatment of wounds of the upper lip and cheek or for repairing the maxillary incisor teeth).

The site of emergence of this nerve can easily be determined by exerting pressure on the maxilla in the region of the infraorbital foramen and nerve. Pressure on the nerve causes considerable pain. Care is exercised when performing an infraorbital nerve block because companion infraorbital vessels leave the infraorbital foramen with the nerve. Careful aspiration of the syringe during injection prevents inadvertent injection of the anesthetic fluid into a blood vessel. The orbit is located just superior to the injection site. A careless injection could result in the passage of anesthetic fluid into the orbit, causing temporary paralysis of the extraocular muscles.

The Mandibular Nerve. This nerve (CN V3) is the inferior division of the trigeminal. CN V3 has three sensory branches that supply the area of skin derived from the embryonic mandibular prominence. It also supplies motor fibers to the muscles of mastication. Of the three divisions of the trigeminal, CN V3 is the only division of CN V that carries motor fibers. The main sensory branches of the mandibular nerve are the buccal, auriculotemporal, inferior alveolar, and lingual nerves. The buccal nerve is a small branch of CN V3 that emerges from deep to the ramus of the mandible to supply the skin of the cheek over the buccinator muscle. It also supplies the mucous membrane lining the cheek and the posterior part of the buccal surface of the gingiva (gum). The auriculotemporal nerve passes medial to the neck of the mandible and then turns superiorly,

posterior to its head and anterior to the auricle. It then crosses over the root of the zygomatic process of the temporal bone, deep to the superficial temporal artery.

As its name suggests, it supplies parts of the auricle, external acoustic meatus, tympanic membrane (eardrum), and skin in the temporal region. The inferior alveolar nerve is the large terminal branch of the posterior division of CN V3; the lingual nerve is the other terminal branch. It enters the mandibular canal through the mandibular foramen. In the canal it gives off branches that supply the mandibular (lower) teeth. Opposite the mental foramen, the inferior alveolar nerve divides into its terminal incisive and mental branches. The incisive nerve supplies the incisor teeth, the adjacent gingiva, and the mucosa of the lower lip. The mental nerve emerges from the mental foramen and divides into three branches, which supply the skin of the chin and the skin and mucous membrane of the lower lip and gingiva (gum).

PAROTIDOMASSETER REGION The boundaries are: superiorly – zygomatic arch; inferiorly – lower edge of mandible; medially – anterior margin of masseter; laterally – ramus of mandible (Fig. 2-34).

The layers are: the skin is thin, mobile; the hypodermic fat is developed moderately, it consist of the superficial vessels and nerves (branches of the facial, mandibular nerves); the fascia proper (f. parotideomasseterica, or investing layer of deep cervical fascia) is divided into two leafs around the parotid gland, which formed the capsule for it.

Fig. 2-34 Parotid gland and Facial nerve (CN VII) on the Face.

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The Parotid Gland The parotid gland (see Fig. 2-34) lies beneath the skin in front of and below the ear. It is contained within the investing layer of the deep fascia, called locally the parotid fascia (f. parotideomasseterica) and the gland can be felt only under pathological conditions.

The boundaries are: anterior – masseter muscle, ramus of mandible, and internal pterygoid muscle; posterior – mastoid process and sternocleidomastoid muscle; superior – external auditory meatus and temporomandibular joint; inferior – sternocleidomastoid muscle and posterior belly of digastric muscle; lateral – investing layer of deep cervical fascia, skin, and platysma muscle; medial – investing layer of deep cervical fascia, styloid process, internal jugular vein, internal carotid artery, and pharyngeal wall.

The parotid duct leaves the anterior edge of the parotid gland midway between the zygomatic arch and the corner of the mouth. It crosses the face in a transverse direction and, after crossing the medial border of the masseter muscle, turns deeply into the buccal fat pad and pierces the buccinator muscle. It enters the inside of the vestibule of mouth near the second upper molar tooth.

The parotid gland receives its arterial supply from the numerous arteries that pass through its substance.

Sensory innervation of the parotid gland is provided by the auriculotemporal nerve, which is a branch

of the mandibular nerve (V3). This division of the trigeminal nerve exits the skull through the foramen ovale.

The auriculotemporal nerve also carries secretomotor fibers to the parotid gland. These postganglionic parasympathetic fibers have their origin in the otic ganglion associated with the mandibular nerve (V3) and are just inferior to the foramen ovale.

Preganglionic parasympathetic fibers to the otic ganglion come from the glossopharyngeal nerve (CN IX).

Structures traversing the Parotid Gland The main trunk of the facial nerve enters the posterior surface of the parotid gland about 1 cm from its emergence from the skull through the stylomastoid foramen about midway between the angle of the mandible and the cartilaginous ear canal. At birth the child has no mastoid process and the stylomastoid foramen is subcutaneous.

About 1 cm from its entrance into the gland, the facial nerve divides to form five branches (see Fig. 2-35): temporal, zygomatic, buccal, mandibular, and cervical.

In most individuals, an initial bifurcation forms an upper temporofacial and a lower cervicofacial division, but six major patterns of branching (from simple to complex) have been distinguished.

The external carotid artery enters the inferior surface of the gland and divides into the maxillary and superficial temporal arteries. The latter gives rise to the transverse facial artery (Fig. 2-35). Each of these bran-

Fig. 2-35 Vasculature of the Face.

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ches emerges separately from the superior or anterior surface of the parotid gland.

The superficial temporal vein enters the superior surface of the parotid gland and receives the middle temporal vein to become the posterior facial vein. Still within the gland, the posterior facial vein divides; the posterior branch joins the posterior auricular vein to form the external jugular vein, while the anterior branch emerges from the gland to enter the common facial vein. Remember, the nerve is superficial, the artery is deep, and the vein lies between them.

The preauricular lymph nodes (see Fig. 2-10) in the superficial fascia drain the temporal area of the scalp, the upper face, and the anterior pinna. Parotid nodes within the gland drain the gland itself, as well as the nasopharynx, nose, palate, middle ear, and external auditory meatus. These nodes, in turn, send lymph to the subparotid nodes and eventually to the nodes of the internal jugular and spinal accessory chains.

The great auricular nerve reaches the posterior border of the sternocleidomastoid muscle and, on the surface of the parotid gland, follows the course of the external jugular vein. It is sacrificed at parotidectomy.

Numbness in the preauricular region, the lower auricle, and the lobe of the ear results from injury to this nerve, but it disappears after 4 to 6 months.

The auriculotemporal nerve, a branch of the mandibular nerve (V3), traverses the upper part of the parotid gland and emerges with the superficial temporal blood vessels from the superior surface of the gland.

Within the gland, the auriculotemporal nerve communicates with the facial nerve. Usually, the order of the structures from the tragus anteriorly is: auriculotemporal nerve, superficial temporal artery and vein, and temporal branch of the facial nerve. The auriculotemporal nerve carries sensory fibers from the trigeminal nerve and motor (secretory) fibers from the glossopharyngeal

nerve. Injury to the auriculotemporal nerve produces Frey’s syndrome, in which the skin anterior to the ear sweats during eating (“gustatory sweating”).

The Parotid Bed Complete removal of the parotid gland reveals the following structures (the acronym VANS may be helpful in remembering them): one Vein: internal jugular; two Arteries: external and internal carotid; four Nerves: glossopharyngeal (CN IX), vagus (CN X), spinal accessory (CN XI), and hypoglossal (CN XII); four anatomical entities starting with “S”: one styloid process and three muscles: styloglossus, stylopharyngeus and stylohyoid (Fig. 2-36).

PROFOUND FACIAL REGION The position of this region is under the mandibular ramus. Profound facial region consists of two intermuscular spaces: interpterygoid and temporopterygoid.

The boundaries of the region are corresponding with the infratemporal fossa. It is an irregular-shaped space lying behind the maxilla, deep to the ramus of the mandible and inferior to the temporal bone.

Bony boundaries of the infratemporal fossa: lateral wall – ramus of the mandible; medial wall – lateral pterygoid plate and free border of this plate followed to the foramen ovale; anterior wall – the infratemporal surface of the maxilla (limited superiorly by the inferior orbital fissure and medially by the pterygomaxillary fissure); posterior wall – the anterior surface of the condylar process (head and neck) of the mandible and the styloid process of the temporal bone; roof – inferior surface of the greater wing of the sphenoid (separated from the temporal fossa by the infratemporal crest).

The foramen ovale in the roof transmits the mandibular division of the trigeminal nerve (V3); inferior boundary – point where the medial pterygoid muscle 1 - mandible; 2 - masseter m.; 3 - parotid duct; 4 - parotid f.; 5 - facial n.; 6, 10 - superficial parotid lymph nodes; 7 - facial a., retromandibular v., deep parotid lymph nodes; 8 - external jugular v.; 9 - parotid gland; 11 - digastric m.; 12 - sternocleidomastoid m.; 13 - posterior part of peripharyngeal space; 14 - superior group of deep cervical lymph nodes; 15 - internal jugular v., glossopharyngeal n.; 16 - superior cervical ganglion of sympathetic trunk, vagus n., accessory n.; 17 - prevertebral muscles and prevertebral f.; 18 - retropharyngeal lymph nodes, retropharyngeal space; 19 - internal carotid a., hypoglossal n.; 20 - pharyngovertebral aponeurosis; 21 - stylopharyngeal aponeurosis; 22 - styloid ðãîcess with muscles started from it; 23 - pharyngeal outgrowth of parotid gland; 24 - pharyngobasilar aponeurosis; 25 - superior part of peripharyngeal space; 26 - palatine tonsil; 27 - superior pharyngeal constrictor m.; 28 - medial pterygoid m.

Fig. 2-36 The Parotid Bed and Peripharyngeal Space.

The figure on the left above represents the level of horizontal section of face.

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inserts into the medial aspect of the mandible near its angle.

Contents of the fossa: (1) Lower portion of the temporalis muscle; (2) Medial and lateral pterygoid muscles; (3) Maxillary artery (Fig. 2-37) (larger of 2 terminal branches of the external carotid artery) and its

branches; (4) Pterygoid plexus of veins (Fig. 2-38) is found around the maxillary artery and may be both superficial and deep to the lateral pterygoid muscle. It drains posteriorly into the maxillary vein and has connections with: the facial vein by way of the deep facial vein, the cavernous sinus in the skull via veins passing

Fig. 2-37 Branches of the Maxillary Artery.

through the foramen ovale, and with middle meningeal veins via the foramen spinosum; (5) Mandibular division of trigeminal nerve (V3) – Inferior alveolar nerve, Nerve to the mylohyoid muscle, Lingual nerve, Buccal nerve, Auriculotemporal nerve, Nerves to the muscles of mastication; (6) Chorda tympani (CN VII); 7) Otic ganglion (associated with autonomic fibers of CN IX).

OPERATIVE SURGERY OF THE FACIAL REGION

Fig. 2-38 Intracranial Venous Connections.

The Features of Facial Wounds Because the face has no distinct deep fascia and the superficial fascia between the cutaneous attachments of the facial muscles is loose, facial lacerations tend to gape (part widely). Consequently the skin has to be sutured with great care to prevent scarring. The looseness of the superficial fascia also enables fluid and blood to accumulate in the loose connective tissue following bruising of the face (e.g., a “black eye”) – Similarly, facial inflammation causes considerable swelling (e.g., the swelling resulting from a bee sting on the bridge of the nose can close both eyes). As a person ages, the skin loses its resiliency. As a result, ridges and wrinkles occur in the skin perpendicular to the direction of the facial muscle fibers. Incisions along these ridges heal with minimal scarring.

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Course of wrinkle lines of the skin is transverse to the fiber direction of facial muscles. Elliptical incisions for removal of skin tumors conform to the direction of wrinkle lines and branches of the facial nerve.

Soft Tissue Injuries The facial soft tissues have a rich blood supply and their debridement should generally be conservative. Important structures at risk in lacerations of the face are the facial nerve, parotid duct, and lacrimal duct system. Facial nerve branches divided anterior to the level of the lateral canthus do not require repair, as the affected muscles tend to reinnervate spontaneously.

Posterior to this level, the nerve branches should be repaired microsurgically.

The parotid duct lies along the middle third of a line drawn between the tragus of the ear and the midportion of the upper lip. Failure to repair the damaged duct may result in an external salivary fistula or chronic parotitis from duct stenosis. The intraoral end can be identified by probing the duct orifice, opposite the upper second molar tooth. The proximal end is identified by expressing saliva from it. Lacerations should be repaired over a stent, which is left in situ for 2 weeks.

Untreated injury to the lacrimal apparatus, near the medial canthus, may result in epiphora or dacryocysti-

tis. Any laceration to the canaliculi, sac, or duct should be probed and repaired over a Silastic stent, which is left in situ for 6 weeks.

Particular anatomical borders of the face require accurate apposition to avoid a visible step and produce optimal cosmetic results. These include the eyelid, nostril and helical margins, the eyebrow, and the vermilion border of the lip.

Mandibular nerve block: local anesthesia may be applied to the mandibular nerve as it emerges from the foramen ovale and enters the infratemporal fossa.

1. Extraoral approach: via the mandibular notch, anesthetizing the auriculotemporal, inferior alveolar, lingual, and buccal nerves. All the skin areas innervated by the mandibular division of the trigeminal are thus anesthetized.

2. Intraoral approach: through the buccal mucosa and buccinator muscle just medial to the ramus of the mandible, near the mandibular foramen. This anesthetizes the inferior alveolar and lingual nerves and their subdivisions. The areas involved are the body and inferior ramus of the mandible, the mandibular teeth and gingivae, and the mucous membrane of the anterior 2/3 of the tongue.

QUESTIONS FOR SELF-CONTROL 1. The regions of the head.

2. The layer-by-layer structure of the scalp.

3. The blood supply of the scalp.

4. The nerve supply of the scalp.

5. Topography of the fronto-parieto-occipital region.

6. Topography of the temporal region.

7. The mastoid region.

8. Topography of the base of the skull.

9. The meninges of the brain.

10. The structure of the brain.

11. The blood supply of the brain.

12. The meninges of the brain.

13. The structure of the facial region of the head.

14. The boundaries of the buccal region.

15. The blood supply of buccal region.

16. The nerve supply of buccal region.

17. The parotidomasseter region.

18. The parotid bed.

19. Topography of the parotid duct.

20. Structure of the profound facial region.

21. The features of facial wounds.

22. The technique of the mandibular nerve block.

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Chapter 3

NECK The neck is a tube providing continuity from the head to the trunk. It extends anteriorly from the lower border of the mandible to the upper surface of the manubrium of the sternum and posteriorly from the superior nuchal line on the occipital bone of the skull to the intervertebral disc between the CVII and TI vertebrae. Within the tube four compartments provide longitudinal organization (Fig. 3-1): - the visceral compartment is anterior and contains parts of the digestive and respiratory systems and several endocrine glands; - the vertebral compartment is posterior and contains the cervical vertebrae, spinal cord, cervical nerves and muscles associated with the vertebral column; - the two vascular compartments are lateral and contain the major blood vessels and the vagus nerve (CN X).

Areas of the Neck The anterior edges of the trapezius muscles are demarcate by the neck on the anterior and posterior areas, or triangles.

The left and right anterior areas of the neck are subdivided into the suprahyoid, infrahyoid and sternocleidomastoid regions as well as into two big triangles – medial and lateral. The medial, or anterior, triangle is limited by the inferior border of the mandible, sternocleidomastoid muscle and the anterior midline of the neck. The lateral (or posterior) triangle is limited by the superior edge of the clavicle, back edge of the sternocleidomastoid muscle and trapezoid muscle.

Within the limits of the medial triangle there are allocated four more triangles (Fig. 3-3): submandibular, submental, carotid and omotracheal, or muscular. Within the borders of the lateral triangle omotrapezoid, or oc-

Fig. 3-1 Compartments of the Neck.

Landmarks of the Neck The laryngeal prominence (“Adam’s apple”) is the important surface feature of the anterior part of the neck (Fig. 3-2). It is produced by the thyroid cartilage, the largest part of the laryngeal skeleton. The thyroid cartilage is located at the level of the 4-5th cervical vertebrae. There are three superficial muscles in the neck: platysma, sternocleido-mastoid, trapezius. The skin of the neck is thin and pliable. The sub-cutaneous connective tissue contains cutaneous nerves and superficial veins. The flat platysma muscle, ascending on the face from the anterior aspect of the neck, is superficial to the main parts of these veins and nerves.

Fig. 3-2 Superficial Landmarks (lateral view).

1 - zygomatic process of the temporal bone; 2 - auriculotemporal nerve and superficial temporal pedicle; 3 - caput mandibulae; 4 - parotid duct; 5 - external auditory canal; 6 - angle of mandible; 7 - facial pedicle; 8 - transverse process of atlas; 9 - inferior parotid pole; 10 - apex of mastoid; 11 - sternocleidomastoid muscle; 12 - submandibular gland; 13 - apex of greater cornu of hyoid bone; 14 - carotid bifurcation; 15 - laryngeal prominence; 16 - cricoid cartilage; 17 - emergence of spinal accessory nerve (peripheral branch); 18 - trapezius and entrance of spinal accessory nerve (peripheral branch); 19 - inferior belly of omohyoid muscle; 20 - external jugular vein; 21 - clavicle; 22 - sternocleidomastoid muscle (clavicular head); 23 - sternocleidomastoid muscle (sternal head).

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cipital and omoclavicular, or subclavian, triangles are allocated.

Fig. 3-3 Areas and triangles of the Neck.

I. Medial big triangle: A. Submandibular, B. Lingual (Pirohov’s), C. Submental, D. Carotid, E. Omotracheal, or Muscular; II. Lateral big triangle: F. Omotrapezoid, or Occipital, G. Omoclavicular, or Subclavian; III. Sternocleidomastoid region.

FASCIAS OF THE NECK Whereas there are only three fascias of the human body is known (superficial, investing and visceral) according to theirs origin from the three germinal layers (ectoderm, mesoderm and endoderm) but Shevkunenko distinguished there are five cervical fasciae (superficial, three leafs of the investing and the visceral) (Fig. 3-4). It is convenient for the applied medicine.

The following classification of the rather complicated fasciae of the neck follows the work of several investigators: 1. Superficial fascia.

2. Investing, or Deep, fascia. a. Anterior, or superficial, layer of investing fascia; b. Middle layer of investing fascia, or fascia of infrahyoid muscles, because it is in front and below hyoid bone only; c. Prevertebral layer (posterior, or deep, layer of investing f.); 3. Visceral fascia, or endocervical fascia, (pretracheal and buccopharyngeal layers).

1. Inferior border of the mandible; 2. Mastoid process; 3. Anterior belly of digastric muscle; 4. Posterior belly of digastric muscle; 5. Hyoid bone; 6. Sternocleidomastoid muscle; 7. Superior belly of omohyoid muscle; 8. Inferior belly of omohyoid muscle; 9. Clavicle; 10. Lateral edge of Trapezoid muscle; 11. Jugular notch.

Fig. 3-4 Fascias of Neck (horizontal section).

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1. Superficial Fascia The superficial fascia lies beneath the skin and is composed of loose connective tissue, fat, the platysma muscle and small unnamed nerves and blood vessels.

The surgeon should remember that the cutaneous nerves of the neck and the anterior and external jugular veins are between the platysma and the deep cervical fascia.

If these veins are to be cut, they must first be ligated.

Because of their attachment to the platysma above and the fascia below, they do not retract; bleeding from them may be serious. For practical purposes, there is no space between this layer and the deep fascia.

2. Investing, or Deep, Fascia a. Anterior, or superficial layer of investing fascia, envelops two muscles (trapezius and sternocleidomastoid), two glands (parotid and submaxillary) and forms two spaces (supraclavicular and suprasternal). It forms the roof of the anterior and posterior cervical triangles and the midline raphe of the strap muscles.

This fascia is attached superiorly to the superior nuchal line of the occipital bone (Fig. 3-5), the mastoid process, the zygomatic arch, the inferior border of the mandible, the hyoid bone and the spinous processes of the cervical vertebrae. Inferiorly, the layer of the investing fascia is attached to the manubrium of the sternum, the clavicle and the acromion and spine of the scapula. Just superior to the sternum, the superficial layer of this fascia divides into two sheets, which are attached to the anterior and posterior surfaces of the manubrium of the sternum, respectively. The superficial layer of the investing fascia also forms the roof of the anterior and posterior triangles of the neck. b. Middle layer of the investing fascia, or fascia of infrahyoid muscles, splits into an anterior portion that envelops the strap muscles and a posterior sheet that envelops the thyroid gland, forming the false capsule of the gland. Together with the superficial fascia and superficial layer of the investing fascia forms the white line of the neck, an aponeurotic narrow strip, a place of joining fascias and aponeurosis of the superficial muscles along the medial sagittal line of the neck. c. Prevertebral, or posterior, layer of the investing fascia lies in front of the prevertebral muscles. It originates from the posterior surface of the sternocleidomastoid and, together with the pretracheal layer of the visceral fascia, forms the carotid sheath. The fascia divides to form a space in front of the vertebral bodies, the anterior layer being the alar fascia and the posterior layer retaining the designation of prevertebral fascia.

The prevertebral fascia forms part of a tubular sheath (fascial sleeve) for the prevertebral muscles that surrounds the vertebral column. It is also continuous with the investing fascia covering the muscular floor of the posterior triangle of the neck. The prevertebral fascia extends from the base of the skull to the third thoracic vertebra, where it fuses with the anterior longitudinal ligament in the posterior mediastinum. The prevertebral fascia extends inferiorly and laterally as the axillary sheath, which surrounds the axillary vessels and brachial plexus.

Pus from an abscess located posterior to the prevertebral fascia is likely to extend into the lateral

parts of the neck, deep to this fascia on the floor of the posterior triangle. Here, it forms a swelling, posterior to the sternocleidomastoid muscle.

3. Visceral Fascia The pretracheal layer envelops some organs of the cervical cavity and lines the wall of it. This thin layer of the visceral cervical fascia is anterior to the trachea and limited to the anterior aspect of the neck; however, it is more extensive than its name implies. It extends inferiorly from the thyroid cartilage and the arch of the cricoid cartilage into the thorax. The pretracheal layer lies deep to the infrahyoid muscles. It splits to enclose the thyroid gland, trachea, esophagus and blends laterally with the carotid sheath. The main vessels of the thyroid gland are located deep to this layer. The visceral fascia descends into the thorax where it blends with the fibrous pericardium in the middle mediastinum.

The buccopharyngeal layer covers the lateral and posterior surfaces of the pharynx and binds the pharynx to the alar layer of the prevertebral fascia.

Infections in the head or cervical region of the vertebral column can spread inferiorly, posterior to the esophagus, into the posterior mediastinum. They can also spread inferiorly, anterior to the trachea and enter the anterior mediastinum. Air from a ruptured trachea, bronchus, or esophagus can pass superiorly in the neck. An unusual source of air in the face and neck may be caused by a dentist’s drill passing through an alveolus (tooth socket). Similarly a small slit in the buccal mucosa, followed by hard blowing with the mouth closed, may result in subcutaneous cervicofacial emphysema. This unusual kind of swollen neck has been reported in glass blowers and in those who play wind instruments.

SPACES OF THE NECK There are many spaces in the neck defined by the fasciae (see Fig. 3-5), but the visceral compartment is the most important. The boundaries of the visceral compartment of the neck are: - anterior: fascia of infrahyoid muscles; - posterior: prevertebral fascia; - lateral: carotid sheath; - superior: hyoid bone and thyroid cartilage; - posteroinferior: posterior mediastinum; - anteroinferior: bifurcation of the trachea at the level of the 4th thoracic vertebra; - contents: part of esophagus, larynx, trachea, thyroid gland and parathyroid glands.

The Retropharyngeal Space consists of loose connective tissue between the prevertebral fascia and the buccopharyngeal layer of the visceral fascia. The buccopharyngeal layer surrounds the pharynx superficially. This “space” permits movement of the pharynx, larynx, trachea and esophagus during swallowing. It is closed superiorly by the base of the skull and on each side by the carotid sheath. It opens inferiorly into the superior mediastinum, which contains the thymus, great vessels of the heart, trachea and esophagus. The retropharyngeal space is of considerable surgical interest 59

Fig. 3-5 Fascias and Spaces of Neck (sagittal cross-section).

because of the structures related to it. Pus located posterior to the prevertebral fascia may perforate this layer and enter the retropharyngeal space. This produces a bulge in the pharynx known as a retropharyngeal abscess, which causes difficulty in swallowing and speaking. Infections in the retropharyngeal space may also extend inferiorly into the superior mediastinum.

Carotid Sheath Beneath the sternocleidomastoid muscle, the investing fascia, the pretracheal fascia and the prevertebral fascia contribute to a fascial tube, the carotid sheath. Within this tube lie the common carotid artery, the internal jugular vein, the vagus nerve and the deep cervical lymph nodes.

The sac of the submandibular gland is pair, contains the submandibular gland, loose cellulose, lymph nodes, facial vessels. Limited by the sheets of the superficial layer of the investing fascia and periosteum of the lower edge of the mandible. It is connected only through openings formed by vessels.

Suprasternal space. It is the interval between two layers of the investing fascia. It encloses the sternal heads of the sternocleidomastoid muscles, the inferior ends of the anterior jugular veins, the jugular venous arch and a few lymph nodes. The space is opened from sides, contains a loose fatty tissue.

Retrosternocleidomastoid cul-de-sac is pair.

This space is limited: the back wall of the vagina of the sternocleidomastoid muscle, fascia of infrahyoid muscle, periosteum of the superioposterior edge of the clavicle. It is connected with the suprasternal space.

Previsceral space is located between the leaves of internal fascia from the level of the hyoid bone to the manubrium of the sternum. Part of this space is selected as pretracheal space. There are lymph nods, thyroid ima artery (8-12%), part of the impar thyroid venous plexus.

Retrovisceral space is located between the visceral fascia (buccopharyngeal layer of it) and the prever60

tebral fascia of the neck, behind a gullet and trachea.

Infections in this space can spread into the posterior mediastinum. There are the internal carotid artery, vagus, glossopharyngeal and accessory nerve, the hyoid bone locates in the back department of the space.

Space of the lateral triangle of the neck is pair, situated between the investing and the prevertebral fasciae. It is limited outside by the carotid sheath and trapezoid muscle.

Prevertebral space is a crack bedding between the prevertebral fascia and neck vertebrae and spreading downward to the 3rd thoracic vertebra. This space includes the sympathetic trunk, phrenic and spinal nerves, deep cervical, levator scapulae, longus colli, anterior, middle and posterior scalene muscles.

STERNOCLEIDOMASTOID REGION Borders of the region are corresponding to muscle.

The layers are: (1) skin thin, mobile; (2) hypodermic fat is expressed moderately; (3) the superficial fascia forms the vagina for the platysma muscle; (4) deep fascia forms the vagina for the sternocleidomastoid muscle. On its surface passes the external jugular vein running into the subclavian vein. The innervation of the muscle is carried out by the accessory nerve (CN XI) and the blood supply from the sternocleidomastoid vessels.

There is the main neurovascular fascicle of the neck under the muscle. It consists of the common carotid artery, internal jugular vein and vagus nerve (CN X).

In the middle of the back edge of the muscle leave branches of the cervical plexus (transverse cervical, supraclavicular, great auricular, lasser occipital, phrenic, accessory nerves).

Structures below the sternocleidomastoid muscle: (1) Ansa cervicalis is on the surface of the carotid sheath.

(2) Carotid sheath containing vagus n., internal jugular v. and common carotid a. (3) Cervical sympathetic trunk is embedded in the dorsomedial wall of the carotid sheath.

TRIANGLES OF THE NECK SUBMANDIBULAR TRIANGLE The submandibular triangle is demarcated by the inferior border of the mandible above and the anterior and posterior bellies of the digastric muscle below. The largest structure in the triangle is the submandibular salivary gland. A number of vessels, nerves and muscles also are found in the triangle.

Layerwise structure of the Submandibular Triangle It is composed of skin, superficial fascia enclosing platysma muscle and fat and the mandibular and cervical branches of the facial nerve (CN VII).

It is important to remember that the skin should be incised 4 to 5 cm below the mandibular angle; the platysma and fat compose the superficial fascia; the cervical branch of the facial nerve (CN VII) lies just below the angle, superficial to the facial artery.

The marginal mandibular branch of facial nerve passes approximately 3 cm below the angle of the mandible to supply the muscles of the corner of the mouth and lower lip. The cervical branch of the facial nerve divides to form descending and anterior branches. The descending branch innervates the platysma and communicates with the anterior cutaneous nerve of the neck.

The anterior branch, the ramus colli mandibularis, crosses the mandible superficial to the facial artery and vein and joins the mandibular branch to contribute to the innervation of the muscles of the lower lip.

Injury to the mandibular branch results in drooling at the corner of the mouth. Injury to the anterior cervical branch produces minimal drooling that will disappear in 4 to 6 months.

The Contents of the Submandibular Triangle The structures of the submandibular triangle, from superficial to deep, are the anterior and posterior facial veins, part of the facial (external maxillary) artery, the submental branch of the facial artery, the superficial layer of the submaxillary fascia (deep cervical fascia), the lymph nodes, the deep layer of the submaxillary fascia (investing cervical fascia) and the hypoglossal nerve (XII).

The facial artery pierces the stylomandibular ligament and so it must be ligated before it is cut to prevent bleeding after retraction. Also, it is important to remember that the lymph nodes lie within the vagina of the submandibular gland in close relationship with it.

Differentiation between the gland and lymph node sometimes is difficult.

The anterior and posterior facial veins cross the triangle in front of the submandibular gland and unite nearby the angle of the mandible to form the common facial vein, which empties into the internal jugular vein near the greater cornu of the hyoid bone. It is necessary to identify, separate, clamp and ligate both these veins.

The facial artery, a branch of the external carotid artery, enters the submandibular triangle under the posterior belly of the digastric muscle and under the stylohyoid muscle. From the beginning, it is under the submandibular gland. After crossing the gland posteriorly, the artery passes over the mandible, lying under the platysma. It can be ligated easily.

The Floor of the Submandibular Triangle The floor of the submandibular triangle, from superficial to deep, include the mylohyoid muscle with its nerve, the hyoglossus muscle, the middle constrictor muscle covering the lower part of the superior constrictor and part of the styloglossus muscle.

The mylohyoid muscles are considered to form a true diaphragm of the floor of the mouth. They arise from the mylohyoid line of the inner surface of the mandible and insert on the body of the hyoid bone into the median raphe. The nerve, a branch of the mandibular division of the trigeminal nerve (CN V), lies on the inferior surface of the muscle. The superior surface is in relationship with the lingual and hypoglossal nerves.

The Basement of the Submandibular Triangle The basement of the triangle, include the deep portion of the submandibular gland, the submandibular (Wharton’s) duct, the lingual nerve, the sublingual artery, the sublingual vein, the sublingual gland, the hypoglossal nerve (CN XII) and the submandibular ganglion.

The submandibular duct lies below the lingual nerve (except where the nerve passes under it) and above the hypoglossal nerve.

The submandibular lymph nodes receive afferent channels from the submental nodes, the oral cavity and the anterior parts of the face. Efferent channels drain primarily into the jugulodigastric, jugulocarotid and juguloomohyoid nodes of the chain accompanying the internal jugular vein (deep cervical chain). A few channels pass by way of the subparotid nodes to the spinal accessory chain.

LINGUAL TRIANGLE (OF PYROGOV) For the purpose of the lingual artery ligation in case of bleeding from the tongue or before the some operations on it the boundaries of the lingual triangle must be defined. This triangle locates within the submandibular triangle and demarcated by the lingual nerve above and the anterior and posterior bellies of the digastric muscle below (Fig. 3-6).

Fig. 3-6 Lingual triangle (of Pyrogov).

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SUBMENTAL TRIANGLE The boundaries of this triangle are: - lateral: anterior belly of digastric muscle - inferior: hyoid bone - medial: midline - floor: mylohyoid muscle - roof: skin and superficial fascia - contents: lymph nodes.

The floor of this unpaired suprahyoid area is formed by the two mylohyoid muscles, which meet in a median fibrous raphe (Fig. 3-7). The apex of the submental triangle is at the symphysis menti and its base is formed by the hyoid bone. The submental triangle contains the submental lymph nodes, which receive lymph from the tip of the tongue, the floor of the mouth, the mandibular incisor teeth and associated gingivae, the central part of the lower lip and the skin of the chin.

Lymph from the submental lymph nodes drains into the submandibular and deep cervical lymph nodes. The submental triangle also contains small veins that unite to form the anterior jugular vein.

Fig. 3-7 Submental Triangle. m - mandible; i - hyoid bone; 1 - anterior belly of digastric muscle; 2 - intermediate tendon of digastric muscle; 3 - posterior belly of digastric muscle; 4 - suprahyoid white line; 5 - mylohyoid muscle; 6 - stylohyoid muscle; 7 - submental artery.

CAROTID TRIANGLE The boundaries are: - posterior: sternocleidomastoid muscle - anterior: anterior belly of omohyoid muscle - superior: posterior belly of digastric muscle - floor: hyoglossus muscle, inferior constrictor of pharynx, thyrohyoid muscle, longus capitis muscle and middle constrictor of pharynx - roof: investing layer of deep cervical fascia - contents (Fig. 3-8): bifurcation of carotid artery ; internal carotid artery (no branches in neck); external carotid artery branches (superficial temporal, internal maxillary, occipital, ascending pharyngeal, sternocleidomastoid, lingual (occasional), external maxillary (occasional) arteries; jugular vein tributaries (superior thy62

roid, occipital, common facial, pharyngeal veins; vagus nerve, spinal accessory nerve, hypoglossal nerve, ansa hypoglossi and sympathetic nerves (partially).

The posterior belly of the digastric muscle – which is between the submandibular and carotid triangles – is a reliable landmark in a dangerous area. Deep to the posterior belly, the following anatomic entities will be found: internal and external carotid arteries, internal jugular vein, glossopharyngeal n. (CN IX), spinal accessory n. (CN XI), hypoglossal n. (CN XII), sympathetic trunk.

Lymph is received by the jugulodigastric, juguiocarotid and juguloomohyoid nodes and by the nodes along the internal jugular v. from submandibular and submental nodes, deep parotid nodes and posterior deep cervical nodes. The lymph passes to the supraclavicular nodes.

MUSCULAR (OMOTRACHEAL) TRIANGLE The boundaries are: - superior lateral: anterior belly of omohyoid muscle - inferior lateral: sternocleidomastoid muscle - medial: midline of neck - floor: prevertebral fascia and prevertebral muscles - roof: investing layer of deep fascia, strap muscles, sternohyoid muscle and cricothyroid muscle - contents (Fig. 3-9): thyroid and parathyroid glands, trachea, esophagus and sympathetic nerve trunk.

Sometimes the strap muscles must be cut during the approach to the thyroid gland. They should be cut across the upper third of their length to avoid sacrificing their nerve supply.

POSTERIOR CERVICAL TRIANGLE The posterior cervical triangle is usually considered to be two triangles, omotrapezoid, or occipital and omoclavicular, or subclavian, divided by the posterior belly of the omohyoid muscle, or perhaps by the spinal accessory nerve.

The boundaries of the posterior triangle are: - anterior: sternocleidomastoid muscle - posterior: anterior border of the trapezius muscle - inferior: clavicle - floor: splenius capitis muscle, levator scapulae muscle and three scalene muscles.

This muscular floor is covered with the investing and prevertebral fascia, between which lie the accessory nerve (CN XI) and a portion of the external jugular vein.

Deep to the fascia are the cervical nerves, the subclavian vessels and the motor nerves to the levator scapulae, the rhomboids, the serratus anterior muscles and the diaphragm.

- roof: superficial layer of the investing cervical fascia - contents: subclavian vessels, cervical nn., brachial plexus, phrenic nerve, accessory n. and lymph nodes.

The external jugular vein courses deeply through the omoclavicular triangle.

The superficial occipital lymph nodes receive lymph from the occipital region of the scalp and the back of the neck. The efferent vessels pass to the deep occipital lymph nodes (usually only one), which drain into the deep cervical nodes along the spinal accessory nerve.

Fig. 3-8 Structures of the Carotid Triangle.

SCALENOVERTEBRAL TRIANGLE It is a deep department of area (inferiomedial).

The boundaries are (Fig. 3-10): - superior: C6 transverse process - lateral: scalene muscles - medial: longus colli muscle - inferior: apex of the pleura - contents: subclavian artery (in close relationship with the apex of pleura), subclavian vein, venous corner, between them vagus nerve and phrenic nerve.

On the bisectrix of the triangle passes the vertebral artery. Along the medial edge of the triangle, between the leafs of the prevertebral fascia is located the cervical department of the sympathetic trunk.

Lymphatics and the Right and Left Thoracic Lymphatic Ducts The thoracic duct originates from the cisterna chyli and terminates in the left subclavian vein (Figs. 3-11 and 3-12). It is approximately 38-45 cm long. The duct begins at about the level of the 2nd lumbar vertebra from the cisterna chyli or, if the cisterna is absent (50%), from the right and left lumbar lymphatic trunks. It ascends to the right of the midline on the anterior surface of the

bodies of the thoracic vertebrae. It crosses the midline between the 7th and 5th thoracic vertebrae to lie on the left side, close to the left esophageal wall. It passes behind the great vessels to the level of the 7th cervical vertebra and descends slightly to enter the left subclavian vein. The duct may have multiple entrances to the vein and one or more of the contributing lymphatic trunks may enter the subclavian or the jugular vein independently. It may be ligated with impunity.

The thoracic duct collects lymph from the whole of the body below the diaphragm, as well as from the left side of the thorax. Lymph nodes may be present at the caudal end, but there are none along its upward course.

Injury to the duct in the supraclavicular lymph node dissections results in copious lymphorrhea. Ligation is the answer. The right lymphatic duct is a variable structure about 1 cm long formed by the right jugular, transverse cervical, internal mammary and mediastinal lymphatic trunks. If these trunks enter the veins separately, there is no right lymphatic duct. When present, the right lymphatic duct enters the superior surface of the right subclavian vein at its junction with the right internal jugular vein and drains most of the right side of the thorax.

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Fig. 3-9 Contents of the Right Muscular (Omotracheal) Triangle.

Fig. 3-10 Structures of the Scalenovertebral triangle.

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Fig. 3-11 The right lymphatic duct is formed by the junction of several lymphatic trunks. If they enter the veins separately, there may be no right lymphatic duct.

Fig. 3-12 The thoracic duct and main left lymphatic trunks. Trunks are variable and may enter the veins with the thoracic duct or separately.

Lymphatic Structures of the Neck Levels of the Nodes From a surgical standpoint, the lymph nodes of the neck are divided into 5 groups, or levels. There is no widespread agreement on the nomenclature of lymph nodes and their division into groups. The “chains” of nodes are shown in Fig. 3-13. The groups composing these chains are listed in Tab. 3-1.

Level I (Submental and Submandibular Nodes).

Level I consists of all lymph nodes within the submental and submandibular triangles.

Level II (Upper Jugular Chain). This level includes all deep jugular lymph nodes in the upper one-third of the neck. Arbitrarily, that area is bounded by the upper one-third of the posterior border of the sternocleidomastoid muscle and the medial border of the posterior belly of the digastric. The boundary extends above to the

occipital area and below to a line corresponding to the pathway of the great auricular nerve, where it crosses the upper part of the sternocleidomastoid obliquely. The subdigastric node also belongs to this level.

Level III (Midjugular Chain). This is a near-triangle formed (below) by the anterior belly of the omohyoid muscle, laterally (posteriorly) by the posterior border of the middle one-third of the sternocleidomastoid muscle and medially by the hyoid bone.

Level IV (Lower Jugular Chain). The boundaries of Level IV consist of the posterior or lateral border of the lower third of the sternocleidomastoid, superiorly of the omohyoid muscle and inferiorly of the clavicle. The juguloomohyoid and deep lower jugular lymph nodes are located within this space.

Level V (Posterior Cervical Triangle). This is the posterior triangle of the neck, which includes the posterior cervical lymph nodes in toto (spinal accessory nodes, inferior horizontal chain, scalene nodes).

Special Lymph Nodes - Virchow’s node, also called the signal node, is located just above the middle third of the left clavicle.

When sufficiently enlarged and firm enough to be palpable, it is usually presumptive evidence of malignant neoplasm below the diaphragm.

- The Delphian node is found just above the thyroid isthmus.

- The neck also contains a number of subepithelial lymphoid structures, the tonsils.

Tonsils The opening between the nasal and oral cavities and the pharynx is guarded by a group of lymphoid structures collectively referred to as the ring of Waldeyer-Pyrohov (Fig. 3-14). On the roof of the nasopharynx, at the superior aspect of the ring of Waldeyer, is the pharyngeal tonsil (adenoids). The lingual tonsils are at the inferior aspect of the ring, on the sides of the base of the tongue. Laterally, the palatine tonsils guard the entrance to the pharynx. There may be a band of superficial lymph nodules, the lateral band, between the pharyngeal and palatine tonsils. These tonsillar organs differ from lymph nodes in that they provide origin to, but do not receive, lymphatic vessels.

Fig. 3-13 The lymph nodes of the neck from Healey’s classification. SH, Superior horizontal chain. IH, Inferior horizontal chain. PV, Posterior vertical chain. IV, Intermediate vertical chain.

AV, Anterior vertical chain.

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Table 3-1 Lymph Nodes and the Lymphatic Drainage of the Head and Neck

PHARYNX

Fig. 3-14 The lymphoid structures of the tonsillar ring of Waldeyer-Pyrohov surrounding the pharynx.

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The pharynx is situated behind the nasal cavities, the mouth and the larynx (see Fig. 3-5). It is somewhat funnel shaped, with its upper, wide end lying under the skull and its lower, narrow end becoming continuous with the esophagus opposite the sixth cervical vertebra. The pharynx has a musculomembranous wall that is deficient anteriorly. Here, it is replaced by the posterior nasal apertures, the oropharyngeal isthmus (opening into the mouth) and the inlet of the larynx. The wall of the pharynx has three layers: mucous, fibrous and muscular.

Muscles of the Pharynx The muscles of the pharynx consist of the superior, middle and inferior constrictor muscles, whose fibers run in a more or less circular direction (Fig. 3-15) and the stylopharyngeus and salpingopharyngeus muscles, whose fibers run in a more or less longitudinal direction. The successive contraction of the constrictor muscles propels the bolus of food down into the esophagus. The lowest fibers of the inferior constrictor muscle, sometimes referred to as the cricopharyngeus muscle, are believed to exert a sphincteric effect on the lower end of the pharynx, preventing the entry of air into the esophagus between the acts of swallowing.

Fig. 3-15 Muscles of the Pharynx and the Gaps between Muscles in the Pharyngeal wall.

The longitudinal muscles elevate the pharynx and larynx during swallowing.

The origins, insertions, nerve supply and actions of the pharyngeal muscles are summarized in Tables 3-2 and 3-3.

Fascia of the Pharynx The pharyngeal fascia is separated into two layers, which sandwich the pharyngeal muscles between them: - a thin layer (buccopharyngeal fascia) coats the outside of the muscular part of the wall; - a much thicker layer (pharyngobasilar fascia) lines the inner surface.

The fascia reinforces the pharyngeal wall where muscle is deficient. This is particularly evident above

the level of the superior constrictor where the pharyngeal wall is formed almost entirely of fascia. This part of the wall is reinforced externally by muscles of the soft palate (tensor and levator veli palatini).

Interior of the Pharynx The pharynx is divided into three parts: nasal, oral and laryngeal.

Nasal Part of the Pharynx The nasal part of the pharynx lies behind the nasal cavities, above the soft palate (Fig. 3-16). When the soft palate is raised and the posterior wall of the pharynx is drawn forward, as in swallowing, the nasal part of the pharynx is shut off from the oral part of the pharynx. It has a roof, a floor, an anterior wall, a posterior wall and lateral walls.

The roof is supported by the body of the sphenoid and the basilar part of the occipital bone. A collection of lymphoid tissue, called the pharyngeal tonsil, is present in the submucosa of this region (see Fig. 3-16).

The floor is formed by the sloping upper surface of the soft palate. The pharyngeal isthmus is the opening in the floor between the free edges of the soft palate and the posterior pharyngeal wall. During swallowing, this communication between the nasal and oral parts of the pharynx is closed by the elevation of the soft palate and the pulling forward of the posterior wall of the pharynx.

The anterior wall is formed by the posterior nasal apertures, separated by the posterior edge of the nasal septum.

The posterior wall forms a continuous sloping surface with the roof. It is supported by the anterior arch of the atlas vertebra.

The lateral wall, on each side, has the pharyngeal opening of the auditory tube. The posterior margin of the tube forms an elevation called the tubal elevation.

The salpingopharyngeus muscle, which is attached to the lower margin of the tube, produces a vertical fold of the mucous membrane called the salpingopharyngeal fold. The pharyngeal recess is a small depression in the lateral wall behind the tubal elevation. A collection of lymphoid tissue in the submucosa behind the opening of the auditory tube is called the tubal tonsil.

Table 3-2

Constrictor Muscles of the Pharynx

Table 3-3 Longitudinal Muscles of the Pharynx

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Fig. 3-16 Mucosal features of the Pharynx. (A) Lateral view. (B) Posterior view with the Pharyngeal Wall opened.

Oral Part of the Pharynx The oral part of the pharynx lies behind the mouth cavity and extends from the soft palate to the upper border of the epiglottis. It has a roof, a floor, an anterior wall, a posterior wall and lateral walls (see Fig. 3-16).

The roof is formed by the undersurface of the soft palate and the pharyngeal isthmus. Small collections of lymphoid tissue are present in the submucosa on the undersurface of the soft palate.

The floor is formed by the posterior 1/3 of the tongue (which is almost vertical) and the interval between the tongue and the anterior surface of the epiglottis. The mucous membrane covering the posterior 1/3 of the tongue is irregular in appearance because of the presence of the underlying lymphoid tissue, the lingual tonsil.

The mucous membrane is reflected from the tongue onto the epiglottis. In the midline is an elevation, called the median glossoepiglottic fold and two lateral glossoepiglottic folds. The depression on each side of 68

the median glossoepiglottic fold is called the vallecula.

The anterior wall opens into the mouth through the oropharyngeal isthmus. Below this opening is the pharyngeal part of the tongue.

The posterior wall is supported by the body of the second cervical vertebra and the upper part of the body of the third cervical vertebra.

The lateral walls on each side have the palatoglossal and the palatopharyngeal arches or folds and the palatine tonsils between them.

The palatoglossal arch is a fold of the mucous membrane covering the underlying palatoglossus muscle.

The interval between the two palatoglossal arches marks the boundary between the mouth and the oral pharynx and is called the oropharyngeal isthmus.

The palatopharyngeal arch is a fold of the mucous membrane on the lateral wall of the oral part of the pharynx behind the palatoglossal arch. It covers the underlying palatopharyngeus muscle.

The tonsillar sinus is a triangular recess on the lateral wall of the oral pharynx between the palatoglossal arch in front and the palatopharyngeal arch behind.

It is occupied by the palatine tonsil.

Palatine Tonsils The palatine tonsils are two masses of lymphoid tissue located in the lateral walls of the oral part of the pharynx in the tonsillar sinuses. Each tonsil is covered by the mucous membrane and its free medial surface projects into the cavity of the pharynx. The surface is pitted by numerous small openings, which lead into the tonsillar crypts. The tonsil is covered on its lateral surface by a layer of fibrous tissue called the capsule.

The tonsil reaches its maximum size during early childhood, but after puberty it diminishes considerably in size.

Relations of the Palatine Tonsil - Anteriorly: The palatoglossal arch.

- Posteriorly: The palatopharyngeal arch.

- Superiorly: The soft palate. Here, the tonsil becomes continuous with the lymphoid tissue on the undersurface of the soft palate.

- Inferiorly: The posterior third of the tongue. Here, the palatine tonsil becomes continuous with the lingual tonsil.

- Medially: The cavity of the oral part of the pharynx.

- Laterally: The capsule is separated from the superior constrictor muscle by loose areolar tissue.

The external palatine vein descends from the soft palate in this loose connective tissue to join the pharyngeal venous plexus. Lateral to the superior constrictor muscle lies the loop of the facial artery. The internal carotid artery lies 2.5 cm behind and lateral to the tonsil.

Blood Supply. The arterial supply to the tonsil is the tonsillar artery, a branch of the facial artery. The veins pierce the superior constrictor muscle and join the external palatine, the pharyngeal, or the facial veins.

Lymph Drainage. The lymph vessels join the upper deep cervical lymph nodes. The most important node of this group is the jugulodigastric node, which lies below and behind the angle of the mandible.

Laryngeal Part of the Pharynx The laryngeal part of the pharynx lies behind the opening into the larynx and the posterior surface of the larynx. It extends between the upper border of the epiglottis and the lower border of the cricoid cartilage.

It has an anterior wall, a posterior wall and lateral walls.

The anterior wall is formed by the inlet of the larynx and by the mucous membrane covering the posterior surface of the larynx.

The posterior wall is supported by the bodies of the third, fourth, fifth and sixth cervical vertebrae.

The lateral wall is supported by the thyroid cartilage and the thyrohyoid membrane. A small but important groove in the mucous membrane, called the piriform fossa, is situated on each side of the laryngeal inlet. It leads obliquely downward and backward from the region of the back of the tongue to the esophagus.

The piriform fossa is bounded medially by the aryepiglottic fold and laterally by the lamina of the thyroid cartilage and the thyrohyoid membrane.

Nerve supply of the pharynx (Fig. 3-17). The nerve supply of the pharynx is from the pharyngeal plexus; the latter is formed from branches of the glossopharyngeal, vagus and sympathetic nerves.

The motor nerve supply is derived from the cranial part of the accessory nerve, which, via the branch of the vagus to the pharyngeal plexus, supplies all the muscles of the pharynx except the stylopharyngeus, which is supplied by the glossopharyngeal nerve.

The sensory nerve supply of the mucous membrane of the nasal part of the pharynx is mainly from the maxillary nerve. The mucous membrane of the oral pharynx is mainly supplied by the glossopharyngeal nerve. The mucous membrane around the entrance into the larynx is supplied by the internal laryngeal branch of the vagus nerve.

Fig. 3-17 Innervation of the Pharynx.

Blood supply of the pharynx. The arterial supply of the pharynx is derived from branches of the ascending pharyngeal, the ascending palatine, the facial, the maxillary and the lingual arteries. The veins drain into the pharyngeal venous plexus, which in turn drains into the internal jugular vein.

Lymph drainage of the pharynx. The lymph vessels from the pharynx drain either directly into the deep cervical lymph nodes or indirectly via the retropharyngeal or paratracheal nodes.

Deglutition (Swallowing) Although we swallow without thinking, deglutition is a complex process whereby food is transferred from the mouth through the pharynx and esophagus into the stomach. The term bolus (L. bolos, lump or choice morsel) is used to describe the mass of food or quantity of liquid that is swallowed at one time. Solid food is masticated (chewed) and mixed with saliva to form a soft bolus during chewing. Deglutition is described in three stages: in the (1) mouth, (2) pharynx and (3) esophagus.

The first stage of swallowing is voluntary, during which the bolus is pushed from the mouth into the oropharynx, mainly by movements of the tongue. The tongue is raised and pressed against the hard palate by the intrinsic muscles of the tongue.

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The second stage of swallowing is involuntary and is usually rapid. It involves contraction of the walls of the pharynx. Breathing and chewing stop and successive contractions of the three constrictor muscles move the food through the oral and laryngeal parts of the pharynx. The bolus of food is prevented from entering the nasopharynx by elevation of the soft palate. The tensor veli palatini and levator veli palatini muscles tense and elevate the soft palate against the posterior wall of the pharynx. These actions close the pharyngeal isthmus, thereby preventing food from entering the nasopharynx. Should a person happen to laugh during this stage, the muscles of the soft palate relax and may allow some food to enter the nasopharynx. In these cases the food, especially if it is liquid, is expelled through the nose.

As the bolus of food passes through the oropharynx, the walls of the pharynx are raised. The contraction of the pharyngeal muscles elevate the pharynx and larynx. Watch someone swallow, particularly a thin man and observe that the laryngeal prominence rises. The palatopharyngeus and stylopharyngeus muscles elevate the larynx and pharynx in swallowing. Palpate your hyoid bone with your thumb and second digit as you swallow and verify that it also rises. The hyoid bone is raised and fixed during swallowing by contraction of the geniohyoid, mylohyoid, digastric and stylohyoid muscles.

Verify that elevation and anterior movement of the hyoid bone precedes elevation of the larynx.

During deglutition the vestibule of the larynx is closed, the epiglottis is bent posteriorly over the inlet of the larynx and the aryepiglottic folds are approximated. These folds provide lateral food channels that guide the bolus of food from the sides of the epiglottis.

The food now passes over the oral surface of the epiglottis and the closed inlet of the larynx. All these actions are designed to prevent food from entering the larynx.

The third stage of swallowing squeezes the bolus from the laryngopharynx into the esophagus. This is produced by the inferior constrictor muscle of the pharynx.

Injury to the recurrent laryngeal nerves (e.g., during a thyroidectomy) results in paralysis of the muscles in the aryepiglottic folds. As a result, the inlet of the larynx does not close completely during swallowing and food may enter the larynx. Choking on food is a common cause of laryngeal obstruction, particularly in persons who have consumed excessive amounts of alcohol, or who have bulbar palsy (degeneration of motor neurons in the brain stem nuclei of CN IX and CN X that supply the muscles of deglutition).

Difficulty in swallowing is called dysphagia.

Young children swallow a variety of objects, most of which reach the stomach and pass through the gastrointestinal tract without difficulty, in some cases the foreign body stops at the inferior end of the laryngopharynx, its narrowest part, or in the esophagus just inferior to the cricopharyngeus muscle, part of the inferior constrictor. Foreign bodies in the pharynx are removed under direct vision through a pharyngoscope (an instrument for examining the interior of the pharynx). Radiographic examinations and MRI will also reveal the presence of a foreign body in the pharynx.

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LARYNX The larynx is an organ between the pharynx and trachea that provides a protective sphincter at the inlet of the air passages and is responsible for voice production. Above it opens into the laryngeal part of the pharynx and below it is continuous with the trachea.

The larynx is located in the anterior portion of the neck. In adult males it is about 5 cm in length and is related posteriorly to the bodies of C3 to C6 vertebrae.

The larynx is shorter in women and children and is situated slightly more superiorly in the neck. This sex difference in the larynx normally develops at puberty in males, at which time all its cartilages enlarge.

The framework of the larynx is made up of cartilages, which are connected by membranes and ligaments and moved by muscles. It is lined by mucous membrane.

The thyroid cartilage (Fig. 3-18) consists of two laminae of hyaline cartilage meeting in the midline in the prominent V angle of the Adam’s apple. The posterior border of each lamina is drawn upward into a superior cornu and downward into an inferior cornu. On the outer surface of each lamina is an oblique line for the attachment of the sternothyroid, the thyrohyoid and the inferior constrictor muscles.

The cricoid cartilage is formed from a complete ring of hyaline cartilage (see Fig. 3-18). It is shaped like a signet ring and lies below the thyroid cartilage. It has a narrow anterior arch and a broad posterior lamina.

Fig. 3-18 Larynx. (a) Disarticulated. (b) Normal approximation.

Chapter 4

THORAX The thorax (or chest) is the region of the body between the neck and the abdomen. The framework of the walls of the thorax (thoracic cage) (Figs. 4-1 and 4-2) is formed posteriorly by the thoracic part of the vertebral column; anteriorly by the sternum and costal cartilages; laterally by the ribs and intercostal spaces; superiorly by the suprapleural membrane; and inferiorly by the diaphragm which separates the thoracic cavity from the abdominal cavity.

The thorax is an irregularly shaped cylinder with a narrow opening (superior thoracic aperture) (see Fig. 4-1) superiorly and a relatively large opening (inferior thoracic aperture) inferiorly. The superior thoracic aperture is open, allowing continuity with the neck; the inferior thoracic aperture is closed by the diaphragm. The thoracic cage protects the lungs and heart and affords attachment for the muscles of the thorax, upper extremity, abdomen, and back.

STRUCTURE OF THE THORACIC WALL The thoracic wall is covered on the outside by skin and by muscles attaching the shoulder girdle to the trunk. It is lined with parietal pleura.

The examination of the chest consists of inspection, palpation, percussion, and auscultation.

Inspection shows the configuration of the chest, the range of respiratory movement, and any inequalities on the two sides. The type and rate of respiration will also be noted.

Palpation will enable the physician to confirm the impressions gained by inspection, especially of the respiratory movements of the chest wall. Abnormal pro-

tuberances or recession of part of the chest wall will be noted. Abnormal pulsations will also be felt and tender areas detected.

Percussion is a sharp tapping of the chest wall with the fingers. This produces vibrations that extend through the tissues of the thorax. Air-containing organs such as the lungs produce a resonant note; conversely, a more solid viscus such as the heart produces a dull note. With practice, it is possible to distinguish the lungs from the heart or the liver by percussion.

Auscultation enables the physician to listen to the breath sounds as the air enters and leaves the respiratory passages. Should the alveoli or bronchi be diseased and filled with fluid, the nature of the breath sounds will be altered. The rate and rhythm of the heart can be confirmed by auscultation, and the various sounds produced by the heart and its valves during the different phases of the cardiac cycle can be heard. It may be possible to detect friction sounds produced by the rubbing together of diseased layers of pleura or pericardium.

To make these examinations, a physician must be familiar with the normal structure of the thorax and must have a mental image of the normal position of the lungs and heart in relation to identifiable surface landmarks.

Since the thoracic wall actively participates in the movements of respiration, many bony landmarks change their levels with each phase of respiration. In practice, to simplify matters, the levels given are those usually found at about midway between full inspiration and full expiration.

Fig. 4-1 Thorax (ventral aspect).

Fig. 4-2 Thorax (dorsal aspect).

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The Landmarks and the Projections of the Thoracic Wall Anterior Chest Wall (Fig. 4-3) The suprasternal notch is the superior margin of the manubrium sterni and is easily felt between the prominent medial ends of the clavicles in the midline. It lies opposite the lower border of the body of the second thoracic vertebra.

The sternal angle (angle of Louis) is the angle made between the manubrium and body of the sternum. It lies opposite the intervertebral disc between the 4th and 5th thoracic vertebrae.

The xiphisternal joint is the joint between the xiphoid process of the sternum and the body of the sternum. It lies opposite the body of the 9th thoracic vertebra.

The xiphoid process lies in the depression where the converging costal margins form the infrasternal angle.

The xiphoid projects over the left lobe of the liver into the epigastric region of the abdomen.

The subcostal, or infrasternal, angle is situated at the inferior end of the sternum, between the sternal attachments of the 7th costal cartilages.

The costal margin is the lower boundary of the thorax and is formed by the cartilages of the 7-10th ribs and the ends of the eleventh and twelfth cartilages. The lowest part of the costal margin is formed by the 10th rib and lies at the level of the 3rd lumbar vertebra.

The clavicle is subcutaneous throughout its entire length and can be easily palpated. It articulates at its lateral extremity with the acromion process of the scapula.

Ribs There are 12 pairs of ribs, all of which are attached posteriorly to the thoracic vertebrae. The upper 7 pairs are attached anteriorly to the sternum by their costal cartilages. The 8-10th pairs of ribs are attached anteriorly to each other and to the 7th rib by means of their costal cartilages and small synovial joints. The 11th and 12th pairs have no anterior attachment and are referred to as floating ribs.

A typical rib is a long, twisted, flat bone having a rounded, smooth superior border and a sharp, thin inferior border. The inferior border overhangs and forms the costal groove, which accommodates the intercostal vessels and nerve.

The first rib lies deep to the clavicle and cannot be palpated. The lateral surfaces of the remaining ribs can be felt by pressing the fingers upward into the axilla and drawing them downward over the lateral surface of the chest wall. The 12th rib can be used to identify a particular rib by counting from below. However, in some individuals, the 12th rib is very short and difficult to feel.

For this reason an alternative method may be used to identify ribs by first palpating the sternal angle and the second costal cartilage.

Nipple In the male it usually lies in the fourth intercostal space about 4 inches (10 cm) from the midline. In the female its position is not constant.

Diaphragm. The central tendon of the diaphragm lies directly behind the xiphisternal joint. In the midrespiratory position the summit of the right dome of the diaphragm arches upward as far as the upper border of the fifth rib in the midclavicular line, but the left dome only reaches as far as the lower border of the fifth rib.

Apex Beat of the Heart. The apex of the heart is formed by the lower portion of the left ventricle. The apex beat is caused by the apex of the heart being thrust forward against the thoracic wall as the heart contracts. The apex beat is normally found in the 5th left intercostal space 9 cm from the midline.

Should you have difficulty in finding the apex beat, have the patient lean forward in the sitting position. In the female with pendulous breasts, the examining fingers should gently raise the left breast from below as the intercostal spaces are palpated.

Axillary Folds. The anterior fold is formed by the lower border of the pectoralis major muscle. This can be made to stand out by asking the patient to press a hand hard against the hip. The posterior fold is formed by the tendon

Fig. 4-3. Anterior view of chest wall with the locations of skeletal structures.

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Trachea. The trachea extends from the lower border of the cricoid cartilage (opposite the body of the sixth cervical vertebra) in the neck to the level of the sternal angle in the thorax. It commences in the midline and ends just to the right of the midline by dividing into the right and left principal bronchi. At the root of the neck it may be palpated in the midline in the suprasternal notch.

Lungs The apex of the lung projects into the neck. It can be mapped out on the anterior surface of the body by drawing a curved line, convex upward, from the sternoclavicular joint to a point 2.5 cm above the junction of the medial and intermediate thirds of the clavicle.

The anterior border of the right lung begins behind the sternoclavicular joint and runs downward almost reaching the midline behind the sternal angle. It then continues downward until it reaches the xiphisternal joint.

The anterior border of the left lung has a similar course, but at the level of the fourth costal cartilage it deviates laterally and extends for a variable distance beyond the lateral margin of the sternum to form the cardiac notch. This notch is produced by the heart displacing the lung to the left. The anterior border then turns sharply downward to the level of the xiphisternal joint.

The lower border of the lung in midinspiration follows a curving line, which crosses the sixth rib in the midclavicular line and the eighth rib in the midaxillary line, and reaches the tenth rib adjacent to the vertebral column posteriorly. It is important to understand that the level of the inferior border of the lung changes during inspiration and expiration.

The posterior border of the lung extends downward from the spinous process of the seventh cervical vertebra to the level of the tenth thoracic vertebra and lies about 4 cm from the midline.

The oblique fissure of the lung can be indicated on the surface by a line drawn from the root of the spine of the scapula obliquely downward, laterally and anteriorly, following the course of the sixth rib to the sixth costochondral junction. In the left lung the upper lobe lies above and anterior to this line; the lower lobe lies below and posterior to it.

In the right lung is an additional fissure, the horizontal fissure, which may be represented by a line drawn horizontally along the fourth costal cartilage to meet the oblique fissure in the midaxillary line. Above the horizontal fissure lies the upper lobe and below it lies the middle lobe; below and posterior to the oblique fissure lies the lower lobe.

Pleura The boundaries of the pleural sac can be marked out as lines on the surface of the body. The lines, which indicate the limits of the parietal pleura where it lies close to the body surface, are referred to as the lines of pleural reflection.

The cervical pleura bulges upward into the neck and has a surface marking identical to that of the apex of the lung. A curved line may be drawn, convex up-

ward, from the sternoclavicular joint to a point 2.5 cm above the junction of the medial and intermediate thirds of the clavicle.

The anterior border of the right pleura runs down behind the sternoclavicular joint, almost reaching the midline behind the sternal angle. It then continues downward until it reaches the xiphisternal joint. The anterior border of the left pleura has a similar course, but at the level of the fourth costal cartilage it deviates laterally and extends to the lateral margin of the sternum to form the cardiac notch. Note that the pleural cardiac notch is not as large as the cardiac notch of the lung. It then turns sharply downward to the xiphisternal joint.

The lower border of the pleura on both sides follows a curved line, which crosses the 8th rib in the midclavicular line and the 10th rib in the midaxillary line, and reaches the 12th rib adjacent to the vertebral column, that is, at the lateral border of the erector spinae muscle. Note that the lower margins of the lungs cross the 6th, 8th, and 10th ribs at the midclavicular lines, the midaxillary lines, and the sides of the vertebral column, respectively, and the lower margins of the pleura cross, at the same points, respectively, the 8th, 10th, and 12th ribs. The distance between the two borders corresponds to the costodiaphragmatic recess.

Heart For practical purposes the heart may be considered to have both an apex and four borders. The apex, formed by the left ventricle, corresponds to the apex beat and is found in the fifth left intercostal space 9 cm from the midline.

The superior border, formed by the roots of the great blood vessels, extends from a point on the 2nd left costal cartilage (remember sternal angle) 1.5 cm from the edge of the sternum to a point on the third right costal cartilage 1.5 cm from the edge of the sternum.

The right border, formed by the right atrium, extends from a point on the third right costal cartilage 1.5 cm from the edge of the sternum downward to a point on the 6th right costal cartilage 1.5 cm from the edge of the sternum.

The left border, formed by the left ventricle, extends from a point on the 2nd left costal cartilage 1.5 cm from the edge of the sternum to the apex beat of the heart.

The inferior border, formed by the right ventricle and the apical part of the left ventricle, extends from the 6th right costal cartilage 1.5 cm from the sternum to the apex beat.

Thoracic Blood Vessels The arch of the aorta and the roots of the brachiocephalic and left common carotid arteries lie behind the manubrium sterni. The superior vena cava and the terminal parts of the right and left brachiocephalic veins also lie behind the manubrium sterni. The internal thoracic vessels run vertically downward, posterior to the costal cartilages, 1.5 cm lateral to the edge of the sternum, as far as the 6th intercostal space. The intercostal vessels and nerve (“vein, artery, nerve� – VAN - is the order from above downward) are situated immediately below their corresponding ribs.

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Posterior Chest Wall (Fig. 4-4) The spinous processes of the thoracic vertebrae can be palpated in the midline posteriorly. The first spinous process to be felt is that of the 7th cervical vertebrae (vertebra prominens). Below this level are the overlapping spines of the thoracic vertebrae. The spines of C1-6 vertebrae are covered by a large ligament, the ligamentum nuchae. It should be noted that the tip of the spinous process of the thoracic vertebra lies posterior to the body of the next vertebra below.

The scapula (shoulder blade) is flat and triangular in shape and is located on the upper part of the posterior surface of the thorax. The superior angle lies opposite the spine of the 2nd thoracic vertebra. The spine of the scapula is subcutaneous, and the root of the spine lies on a level with the spine of the 3rd thoracic vertebra.

The inferior angle lies on a level with the spine of the 7th thoracic vertebra.

The Thoracic Apertures The bony thorax has two apertures or openings.

The superior thoracic aperture is often referred to as the thoracic inlet, and the inferior thoracic aperture is sometimes called the thoracic outlet.

The Superior Thoracic Aperture The head, neck, and limbs communicate with the thoracic cavity through the thoracic inlet or superior thoracic aperture. Through this relatively small, kidneyshaped opening (about 5 cm anteroposteriorly and 11 cm transversely) pass structures entering and leaving the thorax, such as the trachea (windpipe), esophagus (gullet), and the great arteries and veins that supply and drain the head, neck, and upper limbs.

This aperture is limited by the body of the first thoracic vertebra posteriorly, the first pair of ribs and their costal cartilages anterolaterally, and the superior end of the manubrium of the sternum anteriorly. As the margin of the aperture slopes inferoanteriorly, the apex

of each lung and its covering of pleura (pleural cupula) project superiorly through the lateral parts of the thoracic inlet.

The Inferior Thoracic Aperture At the thoracic outlet or inferior thoracic aperture, the thoracic cavity is separated from the abdominal cavity by the musculotendinous thoracic diaphragm.

Most structures that pass from the thorax to the abdomen, or vice versa, go through openings in the diaphragm (e.g., the inferior vena cava, aorta, and esophagus). The thoracic outlet is uneven and is much larger than the superior thoracic aperture.

The inferior thoracic aperture, which slopes inferoposteriorly, is limited by the 12th thoracic vertebra posteriorly, the 12th pair of ribs and costal margins anterolaterally, and the xiphisternal joint anteriorly.

On its way to the upper limb, the subclavian artery crosses the first rib, producing a distinct groove.

This artery may be compressed where it passes over this rib, producing vascular symptoms, e.g., pallor, coldness, and cyanosis (blue color) of the hands. Less frequently, nerve pressure symptoms (numbness and tingling) in the digits result from pressure on the inferior trunk of the brachial plexus. These conditions have been described under several different terms (e.g., the thoracic inlet syndrome), depending on what the author thought was the cause of the symptoms.

Usually the condition is called the neurovascular compression syndrome. The designation thoracic inlet syndrome has also been used to describe the signs and symptoms resulting from multiple enlarged lymph nodes that constrict the superior thoracic aperture or thoracic inlet. These nodes usually enlarge as the result of infiltration of them by malignant cells from a lymphosarcoma, a lymphatic tumor. As a result, blood does not drain normally from the head, neck, and upper limbs and they become congested with blood and appear swollen.

Anatomic and Physiologic Changes in the Thorax with Aging Certain anatomic and physiologic changes take place in the thorax with advancing years: - The rib cage becomes more rigid and loses its elasticity as the result of calcification and even ossification of the costal cartilages; this also alters their usual radiographic appearance.

- The stooped posture (kyphosis), so often seen in the old because of degeneration of the intervertebral discs, decreases the chest capacity.

- Disuse atrophy of the thoracic and abdominal muscles can result in poor respiratory movements.

- Degeneration of the elastic tissue in the lungs and bronchi results in impairment of the movement of expiration.

These changes, when severe, diminish the efficiency of respiratory movements and impair the ability of the individual to withstand respiratory disease.

Fig. 4-4 Surface landmarks of the Posterior Thoracic Wall.

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Coordinate System of the Thoracic Wall The horizontal and the vertical imaginary lines are used to describe surface locations on the anterior and posterior chest walls.

Horizontal Lines of Orientation These lines correspond to the ribs and intercostal spaces.

Vertical Lines of Orientation Midsternal line: Lies in the median plane over the sternum.

Sternal line: Runs vertically downward over the edge of sternum.

Parasternal line: Lies between the sternal line and midclavicular line.

Midclavicular line: Runs vertically downward from the midpoint of the clavicle.

Anterior axillary line: Runs vertically downward from the anterior axillary fold.

Midaxillary line: Runs vertically downward from a point situated midway between the anterior and posterior axillary folds.

Posterior axillary line: Runs vertically downward from the posterior axillary fold.

Scapular line: Runs vertically downward on the posterior wall of the thorax, passing through the inferior angle of the scapula.

Paravertebral line: Lies between the scapular line and vertebral line.

Vertebral line: Lies vertically over the transverse processes of the thoracic vertebrae.

Posterior sagittal line: Lies in the median plane over the spinous processes of the thoracic vertebrae.

Superficial layer of the thoracic wall The skin of the anterior thoracic areas is thin and mobile, but behind it is thicken. The superficial fascia is composed of loose connective tissue. The hypodermis contains a variable amount of fat, sweat glands, blood and lymphatic vessels and nerves. Some blood vessels and nerves are forms the neurovascular fascicles, which provide the blood supply of the superficial soft tissues: - lateral thoracic artery and veins, long thoracic nerve; - superior thoracic artery and veins, supraclavicular nerves; - thoracoacromial artery and veins, lateral pectoral nerve; - cutaneous branches from the intercostal nerves and vessels.

Mammary Gland The mammary (lactiferous) gland, or breast, is a modified sweat gland; this explains why it has no special capsule or sheath. It lies in the superficial fascia, anterior to the thorax (see Fig. 4-5). The deep aspect of the breast is separated from the pectoral muscles by

THE REGIONS OF THE THORAX There are 5 regions of the anterior chest wall and 5 regions of the posterior chest wall.

The lateral boundaries between them are the left and right midaxillary lines.

The regions of the anterior chest wall are: - sternal region (unpaired) - anterosuperior region (left and right) - anteroinferior region (left and right) The regions of the posterior chest wall are: - vertebral region (unpaired) - scapular region (left and right) - subscapular region (left and right) LAYERS OF THE THORACIC WALL Conventionally there are three layers of the thoracic wall (Fig. 4-5): - Superficial layer (skin; subcutaneous fatty tissue with the superficial blood vessels and nerves; superficial fascia with the mammary glands); - Medium layer (investing, or pectoral, fascia; muscles); - Deep layer (bones of the thoracic cage; intercostal spaces; internal thoracic vessels; transverses thoracic muscles; visceral, or endothoracic, fascia; parietal pleura).

Fig. 4-5 Sagittal section through the nonlactating female breast and anterior thoracic wall.

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the deep fascia. Between the breast and deep fascia, there is an area of loose connective tissue that contains little fat. This zone, referred to as the retromammary space (bursa), allows the breast to move freely on the deep fascia covering the pectoralis major muscle.

Although easily separated from the deep fascia, the mammary gland is firmly attached to the skin of the breast by suspensory ligaments (Cooper’s ligaments).

These fibrous bands, which support the breast, run between the skin and the deep fascia. The rounded contour and most of the bulk of the breasts are produced by fat lobules, except during pregnancy and lactation when the mammary glands enlarge. The shape of the breast varies considerably in different persons and races and in the same person at different ages.

During puberty the lactiferous ducts undergo branching and there is an increased deposition of fat.

As a result, progressive enlargement of the breasts occurs. In some women the breasts enlarge slightly during their menstrual cycles owing to the increase in gonadotropic hormones. During pregnancy the breasts enlarge greatly owing to the formation of new glandular tissue. The milk-secreting cells, referred to as alveoli, are arranged in grapelike clusters or lobules. Although the mammary glands are prepared for secretion by midpregnancy, milk is not secreted until after delivery of the fetus and placenta. Colostrum, a creamy white to yellowish premilk fluid, may be expressed from the nipples during the last trimester of pregnancy. Near term, colostrum often leaks from the nipples.

In multiparous women (those who have borne several children), the breasts may become large and pendulous. In elderly women the breasts are small and wrinkled owing to the decrease in adipose and glandular tissue. Although breasts vary markedly in size, their roughly circular bases are fairly constant and have the following limits in well-developed females: vertically from the second to sixth ribs and laterally from the edge of the sternum to the midaxillary line. Two-thirds of the breast rest on the pectoralis major muscle; one-third covers the serratus anterior muscle. Its inferior border overlaps the superior part of the rectus sheath.

The skin of the breasts around the nipples is called areolae. The lactiferous ducts give rise to buds that form 15 to 20 lobules of glandular tissue, which constitute the mammary gland. Each lobule is drained by a lactiferous duct, which opens on the nipple. These ducts extend from the nipple in a manner similar to spokes of a wheel. Deep to the areola, each duct has a dilated portion called the lactiferous sinus, in which milk accumulates during lactation.

Accessory breasts (polymastia) or nipples (polythelia) may occur superior or inferior to the normal breasts. Usually supernumerary breasts consist of a nipple and areola that may be mistaken for a mole or nevus (birthmark). They may appear anywhere along a line extending from the axilla to the groin; this is the location of the embryonic mammary ridge.

A transient increase in the size of the breasts of boys commonly occurs during puberty; however, in some boys with the Klinefelter syndrome (over 50%), the 94

breasts enlarge during puberty and usually increase slowly in size over a period of years. Enlargement of the breasts (gynecomastia) is often the presenting symptom in young men with this syndrome, who usually have an XXY sex chromosome complex.

The areolae contain numerous sebaceous glands, which enlarge during pregnancy and secrete an oily substance that provides a protective lubricant for the areola and nipple. The areolae, variable in size, are pink in white nulliparous women (those who have not borne children). There is no fat beneath the areolae. During the first pregnancy the areolae of white women change permanently to brown; the depth of colour depends on the woman’s complexion.

The nipples are conical or cylindrical prominences that are located in the center of the areolae. There is no fat in the nipples. In nulliparous women they are usually located at the level of the fourth intercostal spaces.

However, the position of the nipple varies considerably and therefore cannot be used as a guide to the fourth intercostal space. The tip of the nipple is fissured and contains the openings of the lactiferous ducts. The nipples are composed mostly of circularly arranged smooth muscle fibers that compress the lactiferous ducts and erect the nipples when they contract.

Arterial Supply of the Breast (Fig. 4-6). There is an abundant blood supply to the breast. The arteries are mainly from the internal thoracic artery via its perforating branches, which pierce the 2nd to 4th intercostal spaces. The breast also receives several branches from the axillary artery, mainly from its lateral thoracic and thoracoacromial branches and lateral and anterior cutaneous branches from the intercostal arteries (in the 3rd to 5th intercostal spaces).

Venous Drainage of the Breast. Veins from the breast drain into the axillary, internal thoracic, lateral thoracic, and intercostal veins. The chief venous drainage is to the axillary vein.

Lymphatic Drainage of the Breast (see Fig. 4-6).

Most lymph passes from the mammary gland along interlobular lymphatic vessels to a subareolar plexus.

From here and other parts of the breast, most lymph vessels follow the veins of the breast to the axilla. Most of the lymphatic drainage (about 75%) is to the axillary lymph nodes, mainly the pectoral group of nodes. They are located along the inferior border of the triangular pectoralis minor muscle, which lies deep to the pectoralis major. From the deep surface of the breast, the lymphatics pass through the pectoralis major muscle and drain into the apical group of axillary lymph nodes.

Lymph from the medial part of the breast drains into the parasternal lymph nodes, which are located within the thorax along the internal thoracic vessels. Lymph from the skin of the breast may pass to the abdominal wall and the opposite breast.

Innervation of the Breast. The breast is supplied by lateral and anterior cutaneous branches of the 2nd to 6th intercostal nerves. These nerves include both sensory and sympathetic fibers, which supply the skin, smooth muscle of the areolae and nipples, blood vessels, and mammary glands.

Fig. 4-6 The Breast.

The breasts are usually equal in size, but if one is larger and more inferior, it is usually the right one. The superolateral quadrant of the breast contains a large amount of glandular tissue and is where most breast cancers develop. This tissue may extend superior to the clavicle and/or inferiorly into the epigastrium. Similarly, glandular tissue from one breast may cross the median plane. The vascularity of the breasts begins to increase early in pregnancy. The increased blood supply dilates the vessels, often making them visible. The connections of the intercostal veins with the vertebral venous plexuses provide a route for spread of cancer cells from the breast to the vertebrae and then to the skull and brain. When carcinoma or CA of the breast invades the retromammary space and attaches to or invades the deep fascia covering the pectoralis major muscle, contraction of this muscle causes the breast to move superiorly. This is a clinical sign of advanced malignant disease of the breast.

The lymphatic and venous drainage of the breasts is of highest importance in the spread of CA of the breast (breast cancer), one of the two most common types of cancer in women. Cancer cells are carried from the breast by lymph vessels to lymph nodes, chiefly those in the axilla. The cells lodge in these nodes where they produce nests of tumor cells called metastases (G. meta, beyond + stasis, a placing). As there is free communication between lymph nodes inferior and superior to the clavicle and between the axillary and cervical

(neck) lymph nodes, metastases from the breast may develop in the supraclavicular lymph nodes, the opposite breast, or in the abdomen. The axillary lymph nodes are the most common site of metastases from CA of the breast. Enlargement of these nodes in a woman therefore suggests the possibility of breast cancer.

Cancerous nodes tend to be hard, but they are not usually tender. The absence of enlarged axillary lymph nodes is no guarantee that metastasis from a breast cancer has not occurred. Often there is dimpling and a thickening of the skin over the site of a CA of the breast, giving it the appearance of an orange peel; this skin change is called “orange skin�. Interference with the lymphatic drainage of the breast produces the leathery thickening, whereas dimpling of the skin is mainly caused by infiltration of cancer cells along the suspensory ligaments. This invasion shortens the ligaments and causes the skin to invaginate (dimple). Subareolar CA may cause inversion of the nipple by the same mechanism.

Methods of Examination of the Breast Mammography (radiographic examination of the breast) is one of the radiographic techniques used to detect breast masses. Mammographs are also used by surgeons to guide them during the removal of breast tumors, cysts, and abscesses. Breast tumors emit more heat than normal breast tissue, consequently thermography is used as a method of measuring and recording heat radiation emitted by the breast. It is sometimes 95

used in conjunction with mammography. Computerized tomography (CT) is also combined with mammography for detection of breast cancer. Before CT scans are taken, an iodide-contrast material is given intravenously to the patient. Breast cancer cells have an unusual affinity for iodide and so become recognizable.

Medium layer of the thoracic wall The investing, or pectoral, fascia is thin but is usually dense and loosely attached to the superficial fascia. It forms an envelope, deep to the superficial fascia, which is adherent to the underlying muscles and constitutes their covering, called epimysium. The pectoral fascia can be separated only by sharp dissection because the epimysium sends septa into the muscles.

This fascia covers the muscles up to their attachment to bone (e.g., the sternum and ribs) and is itself attached to the periosteum of bones. The part of investing fascia between the clavicle and the upper edge of pectoralis minor muscle is named clavipectoral.

Muscles of the Thorax Many muscles are attached to the ribs, such as the anterolateral muscles of the abdomen and some back muscles (Fig. 4-7; Tabs. 4-1, 4-2). The pectoral

muscles, covering the anterior thoracic wall, usually act on the upper limbs, but the pectoralis major can also function as an accessory muscle of respiration to expand the thoracic cavity when inspiration is deep and forceful. In addition, the serratus anterior muscle, which protrudes the scapula, runs around the anterolateral surface of the thorax from the scapula. It is also an accessory muscle of respiration.

Accessory Muscles of Respiration The accessory muscles of respiration (pectoralis major and serratus anterior) are often used by patients with respiratory problems or heart failure when they struggle to breathe. They hold onto a table to fix their pectoral girdles (clavicles and scapulae) so these muscles can act on their attachments to the ribs.

Deep layer of the Thorax Intercostal spaces The spaces between the ribs are called intercostal spaces (Fig. 4-8). Each space contains three muscles of respiration: the external intercostal, the internal intercostal, and the innermost intercostal muscle. The innermost intercostal muscle is lined internally by the endothoracic fascia, which is lined internally by the

Fig. 4-7 Muscles and fascia of the pectoral region.

Table 4-1 Muscles of the Pectoral Region

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Table 4-2 Muscles of the Thoracic Wall

Fig. 4-8 Intercostal Space. (A) Anterolateral view. (B) Details of an Intercostal Space and relationships.

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parietal pleura. The intercostal nerves and blood vessels run between the intermediate and deepest layers of muscles. They are arranged in the following order from above downward: intercostal vein, intercostal artery, and intercostal nerve (i.e., VAN).

Intercostal arteries and veins Each intercostal space contains a large single posterior intercostal artery (see Figs. 4-8, 4-9) and two small anterior intercostal arteries.

The posterior intercostal arteries of the first two spaces are branches from the superior intercostal artery, a branch of the costocervical trunk of the subclavian artery. The posterior intercostal arteries of the lower nine spaces are branches of the descending thoracic aorta.

The anterior intercostal arteries of the first six spaces are branches of the internal thoracic artery. The anterior intercostal arteries of the lower spaces are branches of the musculophrenic artery, one of the terminal branches of the internal thoracic artery.

Each intercostal artery gives off branches to the muscles, skin, and parietal pleura. In the region of the breast in the female, the branches to the superficial structures are particularly large.

The corresponding posterior intercostal veins drain backward into the azygos or hemiazygos veins, and

the anterior intercostal veins drain forward into the internal thoracic and musculophrenic veins.

Intercostal nerves The intercostal nerves are the anterior rami of the first 11 thoracic spinal nerves (see Fig. 4-9). The anterior ramus of the 12th thoracic nerve lies in the abdomen and runs forward in the abdominal wall as the subcostal nerve.

Each intercostal nerve enters an intercostal space between the parietal pleura and the posterior intercostal membrane. It then runs forward inferiorly to the intercostal vessels in the subcostal groove of the corresponding rib, between the innermost intercostal and internal intercostal muscle. The first six nerves are distributed within their intercostal spaces. The seventh to ninth intercostal nerves leave the anterior ends of their intercostal spaces by passing deep to the costal cartilages, to enter the anterior abdominal wall. In the case of the 10th and 11th nerves, since the corresponding ribs are floating, these nerves pass directly into the abdominal wall.

Branches of the intercostal nerves - Rami communicantes connect the intercostal nerve to a ganglion of the sympathetic trunk. The gray ramus joins the nerve medial to the point at which the white ramus leaves it.

Fig. 4-9 Arteries and Nerves of the Thoracic Wall.

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- A collateral branch, which runs forward inferiorly to the main nerve on the upper border of the rib below.

- A lateral cutaneous branch, which reaches the skin on the side of the chest. It divides into an anterior and a posterior branch.

- An anterior cutaneous branch, which is the terminal portion of the main trunk, reaches the skin near the midline. It divides into a medial and a lateral branch.

- Numerous muscular branches are given off by the main nerve and its collateral branch.

- Pleural sensory branches to the parietal pleura.

- Peritoneal sensory branches to the parietal peritoneum (seventh to eleventh intercostal nerves only).

The first intercostal nerve is joined to the brachial plexus by a large branch that is equivalent to the lateral cutaneous branch of typical intercostal nerves. The remainder of the first intercostal nerve is small, and there is no anterior cutaneous branch.

The second intercostal nerve is joined to the medial cutaneous nerve of the arm by a branch, called the intercostobrachial nerve that is equivalent to the lateral cutaneous branch of other nerves. The second intercostal nerve therefore supplies the skin of the armpit and the upper medial side of the arm. In coronary artery disease, pain is referred along this nerve to the medial side of the arm.

With the exceptions noted, the first six intercostal nerves therefore supply (a) the skin and the parietal pleura covering the outer and inner surfaces of each intercostal space, respectively, and (b) the intercostal muscles of each intercostal space and the levatores costarum and serratus posterior muscles. In addition, the seventh to the eleventh intercostal nerves supply (a) the skin and the parietal peritoneum covering the outer and inner surfaces of the abdominal wall, respectively, and (b) the anterior abdominal muscles, which include the external oblique, internal oblique, transversus abdominis, and rectus abdominis muscles.

The Dermatomes Through the cutaneous branches of the dorsal and ventral rami, each spinal nerve supplies a continuous strip of skin, which extends from the posterior midline to the anterior midline. These strips of skin are called dermatomes (Fig. 4-10). This term is derived from Greek and means skin slices. The thoracic and abdominal dermatomes are arranged in a segmental fashion because the thoracoabdominal nerves arise from segments of the spinal cord. There is considerable overlapping of contiguous or closely related dermatomes; i.e., each segmental nerve overlaps the territories of its neighbours. The first two intercostal nerves (Tl and T2) supply the upper limbs in addition to supplying the thoracic wall. The inferior five intercostal nerves (T7 to T11) supply the abdominal wall, as well as the thoracic wall.

Bones of the Thoracic Wall The osteocartilaginous thoracic cage is formed by part of the vertebral column (12 thoracic vertebrae and intervertebral discs); 12 pairs of ribs and costal cartilages, and the sternum (see Figs 4-1 and 4-2). The ribs and costal cartilages form the largest part of the thoracic cage.

The Thoracic Vertebrae Thoracic vertebrae are unique in that they have facets on their bodies and transverse processes for articulation with the ribs (T11 and T12 are exceptions).

Two demifacets are located laterally on the bodies of T2 to T9. The superior demifacet articulates with the head of its own rib and the inferior demifacet articulates with the head of the rib inferior to it. The costal facets of other vertebrae vary somewhat. T1 has a single costal facet for the head of the first rib and a small demifacet for the cranial part of the second rib. T10 has only one costal facet which is partly on its body and partly on its pedicle. T11 and T12 have only a single costal facet on their pedicles.

Fig. 4-10 The Dermatomes.

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