Head, Neck & Spine - Jack Roberts by ICSM SU

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

LCRS – Anatomy of the Head, Neck and Spine The Vertebral Column and the Spinal Cord 1. Recognise and name the following parts of a typical vertebra in osteological specimens or in suitable imaging: body, pedicle, lamina, transverse process, spinous process, articular surfaces Spinous Process

Lamina

Superior Articular Facet Transverse Processes

Pedicle

Spinal Canal

Vertebral Body

2. Recognise the distinctive features of cervical, thoracic and lumbar vertebrae Cervical Vertebrae (7)

Thoracic Vertebrae (12)

Lumbar Vertebrae (5)

Sacral Vertebrae (5 fused)

A triangular vertebral foramen Vertebral body is short in height and square shaped A foramen in each transverse process for arteries and veins A bifid (two-pronged) spinous process, except C1 and C7 The atlas and axis (C1 and C2) are specialised for movement

Larger and stronger Facets for rib articulation (inferior and superior costal facets, and transverse costal facet) A spinous process orientated in a marked inferior fashion Vertebral foramen circular Vertebral body is somewhat heart-shaped from above

Identifiable by their large size, particular of the body Have rounded upper and lower facets to prevent rotation Thin, long transverse processes (except LV) Vertebral body is cylindrical Vertebral foramen is triangular in shape

Sacral vertebrae are fused to form the sacrum Triangular in shape Concave anterior surface L shaped facets – articulation with pelvic bones

Coccyx (3-4 fused) Absence of vertebral arches and canal

3. Explain the roles of intervertebral discs, ligaments and muscles in load bearing in the vertebral column Joints The two major types of joints between vertebrae are: o Symphyses between vertebral bodies o Synovial joints between articular processes Each vertebra has a total of 6 joints with adjacent vertebrae (4 synovial (2 above, 2 below) and 2 symphyses (one above, one below) In between each vertebrae (C2 to S1) are intervertebral discs which consist of: o An annulus fibrosus – tough hyaline cartilaginous rim- limits rotation o A nucleus pulposus – fibrocartilagenous core – softer, probably derived from remnants of the notochord – absorbs compression forces between vertebrae Rupture of the annulus fibrosus may allow the softer nucleus pulposus to herniate which can compress the spinal cord or segmental nerve roots – slipped disc There is no disc between the base of the skull and C1, or between C1 and C2 due to specialised movements which occur here The synovial joints between articular processes on adjacent vertebrae are the zygapophysial joints In cervical regions, the zygapophysial joints slope inferiorly from anterior to posterior. This orientation facilitates flexion and

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine extension In thoracic regions, the joints are oriented vertically and limit flexion and extension, but facilitate rotation. In lumbar regions, the joint surfaces are curved and adjacent processes interlock, thereby limiting range of movement, though flexion and extension are still major movements in the lumbar region Although the movement between any two vertebrae is limited, the summation of movement among all vertebrae results in a large range of movement by the vertebral column Movements by the vertebral column include flexion, extension, lateral flexion, rotation, and circumduction Ligaments of the vertebral column: Ligamentum nuchae – triangular, sheet like structure – Skull to CVII Supraspinous ligaments – between the tips of the spinous processes – CVII to the sacrum Interspinous ligaments – between adjacent spinous processes Ligamentum flava – between vertebral arches connecting adjacent laminae – this ligament is pierced during a lumbar puncture. Form part of posterior surface of vertebral canal. o Predominantly elastic tissue o Resist separation of laminae in flexion o Assist in extension back to anatomical position Anterior longitudinal ligament – covers and connects the anterior surfaces of the vertebral bodies and intervertebral discs – base of skull to anterior surface of the sacrum o The anterior longitudinal ligament is mostly commonly damaged in whiplash Posterior longitudinal ligament – runs within the vertebral canal on the posterior surface of the vertebral bodies - anterior surface of vertebral canal Articular ligaments – all synovial articulations (facet joints) are surrounded by ligaments

Muscles of the vertebral column: Contraction of the muscles of the abdominal wall causes flexion and lateral flexion

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine There are two main groups of muscle in the back: o Superficial extrinsic muscles including trapezius, latissimus dorsi, rhomboid minor/major, levator scapulae o Deep intrinsic muscles, particularly the erector spinae muscles, which are important in controlling the movement of the vertebral column. The large muscle bulk is posterior and lateral to the vertebral column

4. Describe the relative extents of antero-posterior flexion, lateral flexion and axial rotation in the major regions of the vertebral column and explain this in terms of skeletal anatomy C1-C7 T1-T6 T7-T12 L1-sacrum

Flexion/extension ++ 0 + ++

Lateral flexion ++ + ++ +

Cervical – is the most flexible part of the spine. The articular surfaces between the vertebrae are almost horizontal and so allow rotation. The neck is slender with less surrounding bulk tissue and so there is less resistance to flexion and extension. Although the intervertebral discs are thin, they are relatively thick compared to the vertebrae. Thoracic – the attachment to ribs limits flexion and extension. Movement is also intervertebral discs. Joints are oriented vertically and limit flexion and extension, but Lumbar – there are large intervertebral discs. The intervertebral articular surfaces are midline of the body) orientated and so whilst these are compatible with flexion/extension and lateral flexion, they are not compatible with rotation.

Rotation ++ + ++ 0 cervical

limited by thin facilitate rotation. sagitally (vertically down the

5. Identify the atlas and axis and explain their functions in head movement Axis = C2 A typical cervical vertebra with the body extended upwards to form the dens (tooth) The dens is the pivot around which C1 rotates Large articular facets on upper and lateral sides for gliding movements with C1 Atlas = C1 Has no body Lies behind the mouth Posterior surface of anterior arch has a facet for articulation with the dens Has inferior articular facets for reciprocal facets on C2 The C1-C2 atlanto-axial joint Midline A synovial joint between the dens and the back of the anterior arch of the atlas, bursa between the dens and the transverse ligament behind Laterally the articular surfaces are flat to allow gliding The transverse ligament separates the dens from the spinal meninges The skull and C1 rotate on C2 as a unit. Excessive rotation at these joints is prevented by ligaments Atlanto-occiptal joints – between C1 and the occipital bone of the skull form synovial by apical ligaments to allow nodding of the head

process

and a synovial

the alar joints linked

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

6. Demonstrate on each other the location of C7, T3, T7, L2 and L4 vertebrae C7 – only cervical vertebrae with a prominent spinous process T3 – level with the medial end of the scapular spine T7 – level with the inferior angle of the scapula L2 – level of lowest rib L4 – Level of the iliac crest

7. State the number of vertebrae in each region of the spine, and how the pairs of spinal nerves are related to them Cervical Thoracic Lumbar Sacral Coccyx Total

Number of vertebrae 7 12 5 5 (fused) 1-4 (fused) 30-33

Number of spinal nerves 8 12 5 5 1 31

Relationship of nerve to vertebra All above corresponding vertebra except for C8 All below corresponding vertebra All below corresponding vertebra All below corresponding vertebra Below (or between if unfused)

8. Explain the arrangement of the meninges around the spinal cord and roots, and indicate any differences from the cranial meninges The spinal cord is surrounded by the meninges which are continuous with the meninges of the brain Pia mater – on the surface of, and inseparable from the spinal cord. On each side of the spinal cord, a longitudinally orientated sheet of pia (denticulate ligament) extends laterally from the cord toward the arachnoid and dura mater. Arachnoid mater – the arachnoid mater is against, but not adherent to the dura mater. Terminates at SII. Between it and the pia matar is the sub-arachnoid space containing CSF. Delicate strands of tissue (arachnoid trabeculae) are continuous with the arachnoid mater on one side and the pia mater on the other, span the subarachnoid space and interconnect the two adjacent membranes. Large blood vessels are suspended in the subarachnoid space by similar strands of material. Dura mater – tough and fibrous. At the point where a spinal nerve passes through the intravertebral foraemen the dura is continued along the nerve as the epineurium. Nerve roots in the subarachnoid space do not have this protection. Between the dura matar and the sub-arachnoid is the subdural space. Outside the dura matar between it and the walls of the bony canal is the extra or epidural space. It contains connective tissue, fat and the internal vertebral venous plexus Difference between spinal and cranial meninge There is no extradural (epidural) space in the cranium as the cranial dura matar is firmly adherent to the skull except at certain sites where they part to form the venous sinuses (principal collecting ducts for blood from the brain) Filum Terminale

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine At the lower margin of the spinal cord at about LII, the pia mater is prolonged (pial part). After the termination on the subarachnoid space (SII) the dura mater is prolonged and attaches to the coccyx (dural part). See Grays page 63 It is formed at the spinal cord withdraws upwards during development Together with the nerve roots forms the cauda equine below LII

9. Identify two major reasons for carrying out lumbar puncture, and explain the basis for the puncture site The vertebral level below L1/L2 is only occupied by CSF (up to S2), and the cauda equine This forms the lumber cistern of CSF – so needles may be inserted without damage to nerves A needle passes through the skin, slightly off centre → through the ligamentum flavum (a give is felt) between the adjacent vertebral laminae → the tip of the needle is in the epidural space → pierces the dura and arachnoid together (another pop/give) into the subarachnoid space→ CSF should pass out In an adult best done at L3/L4 – the highest point of the iliac crest. In a child it is performed one or two vertebral spaces lower Carried out to obtain a sample of CSF for examination (e.g. suspected meningitis) and for spinal anaesthesia (agent injected into subarachnoid space) Epidural anaesthesia – a liquid agent can be injected into the epidural space to anaesthetise the spinal nerve roots The sacral hiatus allows administration of caudal epidural anaesthesia

10. Explain the danger of carrying out lumbar puncture without excluding the presence of raised intracranial pressure In cases of intracranial pressure, the sudden release of CSF pressure, associated with the procedure of a lumbar puncture, could cause the brainstem to herniate through the foramen magnum and into the vertebral canal. This would be fatal.

11. Outline the steps taken to avoid neurological complication in casualties with a possibility of cervical spine injury At the scene signs of cervical spine injury Low BP with bradycardia – loss of sympathetic tone, vasodilation Large erection – Custer’s last stand Flaccid paralysis Large bladder with inability to micturate At the scene management Assume all patients have an intact spinal cord with an unstable fracture All patients who can’t tell you they have no neck pain must be assumed to have neck pain Use cervical collar and blocks to immobilise neck – only remove when C spine is clear In hospital Primary injury is done, damage cannot be reversed – aim is to reduce further damage Take lateral and AP C Spine – if fracture image with CT/MRI Give steroids – probably prevent the death of around 1cm of spinal cord – could be the difference between being independent or not in the cervical region. Treat any other symptoms e.g. low BP

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine 12. Explain in anatomical terms the most common causes of back pain The lower spine is subject to increased stresses of weight-bearing and so the lumbar region is most commonly affected We tend to abuse our backs, particularly when lifting heavy objects. Extending the spine from the fully flexed position under a heavy load can inflame intervertebral joints or place unequal pressure on the intervertebral disks, leading to local joint pain and referred neurological pain, if there is also pressure on the spinal nerve. Additional attempts to rotate the spine at the same time creates extra stress on the lumbar joints.

13. Describe the most common abnormalities of spinal curvature Scoliosis – lateral deviation of the vertebral column Kyphosis – excess thoracic curvature, “hump back” Lordosis – excess lumbar curvature, e.g. due to obesity

The Cranium and Brain 1. Demonstrate on a skull and in radiographs the following bones: frontal, parietal, temporal (squamous, petrous and mastoid process), ethmoid, sphenoid (body and wings) and occipital

Frontal Bone

Parietal Bone

Sphenoid Bone (wing)

Occipital Bone

Nasal Bone

Zygoma

Temporal Bone Mastoid Process

Maxilla

Styloid Process

Mandible

Anterior Cranial Fossa Ethmoid bone (cribriform plate) Lesser wing of sphenoid Greater wing of sphenoid Middle Cranial Fossa Petrous of Temporal Bone Foramen Magnum Posterior Cranial Fossa

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine 2. Identify both on the brain and in x-ray, CT and MRI images the following: ventricles, cerebral hemispheres, thalamus, hypothalamus, internal capsule, basal ganglia, brainstem, optic chiasm and pituitary gland MRI 1

Lateral ventricle [may be cut through twice in horizontal or coronal plane]

Third ventricle [may look like a hole or a slit in coronal and horizontal plane, depending on angle of section]

Fourth ventricle

Aqueduct

Corpus callosum [may be cut through twice in horizontal plane] – connects right and left hemisphere

Frontal lobe

Occipital lobe

Parietal lobe

Temporal lobe

Basal ganglia [may be more than one part] – group of nuclei – motor, cognition, emotions, and learning

Thalamus

Internal capsule [both anterior and posterior limbs seen in horizontal plane]

Optic chiasma

Midbrain

Pons

Medulla

Cerebellum

very similar – see notes

3. Identify the different tissue components of the scalp Skin –contains many sweat and sebaceous glands and hair follicles. It is covered in hair with lots of vasculature Connective tissue – richly vascularised that is well supplied by cutaneous nerves Aponeurosis – also known as epicranial aponeurosis. A membranous sheet and tendon of the epicranius muscles Loose connective tissue – many spaces which allows the ‘scalp’ to move over the pericranium Pericranium – a dense layer of connective tissue, which is continuous with endocranium in the cranial sutures. It is important to avoid infection of lacerations to the scalp as it can spread infection into the cranial cavity via emissary vessels which go through the skull – thus bypassing the blood-brain barrier See picture below

4. Demonstrate the relationship between the brain and the different cranial fossae Anterior cranial fossa – frontal lobes of brain Middle cranial fossa – temporal lobes of brain Posterior cranial fossa – cerebellum and brainstem

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine 5. Describe the structure and function of the meninges

Inner layer inseparable from the brain = pia mater Middle layer = arachnoid Outer layer = dura mater Between the arachnoid and pia = sub arachnoid space – continuous and containing CSF The contours of the dura reflect the folds of the brain o Falx Cerebri – separates the two cerebral hemispheres – attached to ethmoid at front and vault above and below o Tentorium cerebelli – separates the cerebellum from the cerebrum - a more or less horizontally arranged sheet extending back from the ridge of the petrous temporal bone to the internal occipital protuberance. It forms a complete diaphragm over the posterior cranial fossa except for the tentorial notch through which the brain stem and surrounding nerves and vessels pass

6. Draw a simple diagram to explain the flow of cerebrospinal fluid in and around the brain CSF is produced by the choroid plexus – a vascular plexus formed where the vessels of the pia mater come into contact with the ependymal lining of the central canal Lateral ventricles → third ventricle → through cerebral aqueduct → fourth ventricle → some enters the central canal of the spinal cord, most enters the subarachnoid space through foramina in the roof of the fourth ventricle → flows around the brain and is absorbed back into the venous circulation through arachnoid villi/granulations in the venous sinuses Hydrocephalous is over production of CSF or reduced absorption

7. Explain the term herniation with respect to the brain and give examples of its neurological consequences Space occupying lesion (eg. blood, tumour, oedema, cyst) in any compartment may raise intracranial pressure and lead to herniation of part of brain.

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine 1) Subfalcine herniation – not usually clinically significant 2) Uncal herniation– affects midbrain – unconsciousness 3) Tonsilar herniation– affects medulla – cardiorespiratory failure

8. Identify on a skull the main exit/entry routes for the cranial nerves and the major blood vessels

Cribiform Plate

Optic Canal

Olfactory (I) Nerve Fibres

Optic Nerve (II) including (central artery of retina) Opthlamic Artery Oculomotor Nerve (III) Trochlear Nerve (IV)

Superior Orbital Opthalmic division of Trigeminal (V) Fissure Abducens Nerve (VI)

Superior Opthalmic Vein

Foramen Rotundum Foramen Ovale

Maxillary Division of Trigeminal Nerve (V)

Mandibular Division of Trigeminal Nerve (V)

Foramen Spinosum Foramen Lacerum

Middle Meningeal Artery and Vein

Carotid Canal

Internal Carotid Artery

Facial Nerve (VII) (including intermediate nerve

Internal Acoustic Vestibulocochlear Nerve (VIII) Meatus Labyrinthine Artery

Glossopharyngeal Nerve (IX)

Hypoglossal Canal Hypoglossal Nerve (XII)

Jugular Foramen

Vagus Nerve (X) Accessory Nerve (XI) Sigmoid Sinus → Internal Jugular Vein

Foramen Magnum

Vertebral Arteries, Medulla of Brain Spinal roots of Accessory (XI) Nerve

9. Draw a simple diagram of the Circle of Willis

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

10. Demonstrate the main venous sinuses

The Superior Saggital Sinus

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine In the midline at the attachment to the falx cerebri to the skull vault Blood in it drains posteriorly and at the internal occipital protuberance turns right, forming the right transverse sinus Transverse sinus turns into the sigmoid sinus as it passes the petrous temporal bone Sigmoid sinus passes through the jugular foramen and becomes the right internal jugular vein The Inferior Saggital Sinus In the midline in the inferior free margin of the flax cerebri Blood in it drains posteriorly and is joined at the tentorium/falx junction by blood from the great cerebral vein emerging at the back of the brain stem They unit to form the straight sinus which passes back in the attachment of the falx and turns left at the internal occipital protuberance becoming the left transverse sinus The pattern mirror this on the right forming the left internal jugular vein o Sometimes the pattern is reversed with the superior saggital sinus turning left and the straight saggital sinus turning right o At the internal occipital protuberance the venous channels may communicate – the confluence of sinuses o Right sided drainage normally bigger than left, indeed the left jugular vein can be absent all together The Cavernous Sinus Formed in the embryo from the coalescence of several venous channels Forms a system of interconnecting caverns around the internal carotid The right and left cavernous sinuses lie either side of the pituitary fossa and communicate with the transverse sinuses and internal jugulars via petrosal sinuses Arachnoid Granulations The dural walls of the sinuses, particular in the superior saggital sinus posses small defects These defects allow underlying arachnoid to billow out into the sinus Only the arachnoid, and endothelium of the sinus separate CSF from venous blood The site of CSF reabsorption

11. Outline how venous anatomy presents opportunities for intracranial infection The facial vein makes clinically important connections with the: o Cavernous sinus – (a venous sinus of the dura mater covering the brain) through the superior ophthalmic vein. o Pterygoid venous plexus – (a network of small veins within the infratemporal fossa) though the inferior ophthalmic and deep facial veins. The facial vein has no valves - blood may pass through it in the opposite direction Venous blood from the face may enter the cavernous sinus Patients with thrombophlebitis of the facial vein (inflammation of the facial vein with secondary thrombus formation) - pieces of an infected clot may extend into the intracranial venous system; producing thrombophlebitis of the cavernous sinus Compression of the thorax can also force venous blood from these areas into the dural sinus system – bypassing the BBB and possibly leading to infection or metasteses

12. Identify the pterion and explain the clinical importance of its relationship to the middle meningeal artery An area on the lateral side of the skull where the frontal, parietal, temporal and sphenoid bones meet Its surface marking is about 4cm above a point 1/3 of the way from ear to eye The middle meningeal artery is a branch of the maxillary artery and enters the middle cranial fossa through thr foramen spinosum The anterior division runs deep to the pterion – the thinnest and weakest part of the cranium Injury at this site can easily tear the artery causing an extradural haemorrhage The MCA also runs deeper to this point and if damaged can cause a subarachnoid haemorrhage

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

Root of the Neck 1. Sketch the thoracic inlet to show the relations of the following structures at the neck-chest interface: 1st thoracic vertebra, 1st ribs and cartilages, manubrium, pleura and lungs, oesophagus, trachea, brachiocephalic veins, vagus nerves, brachiocephalic artery, left common carotid and subclavian arteries, sympathetic trunks, left recurrent laryngeal nerve, phrenic nerves

of C1 C2 C3

Vertebral Levels the neck – open mouth – superior ganglion – body of hyoid C4 – upper border of

cervical

thyroid cartilage, bifurcation of the common carotid artery C6 – cricoid cartilage, middle cervical ganglion C7 – inferior cervical ganglion 3 main compartments in the column of the neck: o Visceral compartment (trachea, oesophagus, thyroid) o Carotid sheath/vascular (vagus nerve, carotid artery, jugular vein, associated with sympathetic chain behind) o Vertebral compartment (vertebral column, nuchal muscles, scalene muscles) 1st Rib The strap muscles are functionally connected to the visceral compartment and move the larynx during swallowing The deep cervical fascia/investing layer is Manubrium made of connective tissue and holds the contents in The sternocleidomastoid provides protection to the carotid sheath when the head is turned

2. Locate the carotid pulse and explain the main uses of this central pulse Main uses of the carotid pulse: o Assessment of pulse rhythm, rate character (easy to find) o Timing of murmurs o To locate the jugular vein The carotid pulse (the pulse that can be felt in the neck) is easily felt by palpating the common carotid artery on either side of the neck, where it lies in a groove between the trachea and the infrahyoid (strap) muscles o Posteriorly lateral to the upper border of the thyroid cartilage

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine 3. Demonstrate the technique for palpation of the cervical lymph nodes and define their field of drainage All nodes eventually drain into the deep cervical nodes of the jugular vein There are 2 basic patterns of lymph nodes: o A ring at the junction of head and neck o Vertical line in the neck There are some deep nodes associated with the larynx which are not on the diagram Lymph drainage Parotid, Masotid & Occipital – drains side of face, ear and scalp Superficial cervical (along the jugular vein) – drains the posterior triangle Submandibular and Submental – drains the inside of the mouth and lips Jugulodigastic – drains the back of the throat Supraclavicular drains all of the head and neck up from the thorax The lymph nodes can become inflamed o Infection – reactive, local, generalised, in the gland itself o Neoplastic – of the node (lymphoma), metastatic

4. Define the boundaries of the anterior and posterior triangles of the neck Boundaries of the posterior triangle Posterior border of sternocleidomastoid Anterior border of trapezius Middle 1/3 of the clavicle Contents of posterior triangle Mainly nerves and blood vessels o External jugular vein o Spinal accessory nerve o Trunks of the brachial plexus, emerging posterior to scalenus anterior o Subclavian artery posterior to scalenus anterior o Subclavian vein anterior to scalenus anterior o Phrenic nerve lying in the anterior surface of scalenus

Boundaries of the anterior triangle Anterior border of sternocleidomastoid The midline The lower border of the mandible Contents of the anterior triangle Mainly muscles o Platysma o Digastric muscle o Strap muscles (infrahyoid) o Mylohyoid Common carotid arteries Internal jugular vein Larynx and trachea

5. Identify the infrahyoid (strap) muscles, mylohyoid and the digastric muscle Key muscles Platysma – supplied by facial nerve Mylohyoid – supplied by mandibular branch of the trigeminal nerve Anterior belly of digastric – supplied by mandibular branch of trigeminal nerve Posterior belly of digastric – supplied by facial nerve The infrahyoid (strap) muscles – omohyoid, sternothyroid, sternohyoid (supplied by ansa cervicalis) and thyrohyoid (supplied by C1 fibres via the hypoglossal nerve)

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

6. Demonstrate on the subject and on prosections the of the roots of the plexus

Superior

– C5, C6

Medial – C7 Inferior – C8, T1

living suitable position and trunks brachial

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine 7. Demonstrate in prosections the position and key relations of the subclavian artery and vein, and brachial plexus

8. Demonstrate the courses of the internal thoracic and vertebral branches of the subclavian artery Branches of the first part of the artery Vertebral artery – supplies the spinal cord, brainstem and brain through foramen in the transverse processes of the cervical vertebrae Internal thoracic artery – supplies the breast, anterior chest wall, anterior abdominal wall , pericardium and diaphragm Thyrocervical trunk – supplies the thyroid (via the inferior thyroid artery), upper scapular and anterior neck *Anatomy workbook – blood supply to the thyroid* Superior thyroid artery, branch of the external carotid Inferior thyroid artery, branch of thyrocervical trunk o In 10% of people also have the thyroid ima artery arising from the brachiocephalic trunk Superior thyroid vein drains in to the internal jugular vein Middle thyroid vein drains in to the internal jugular vein Inferior thyroid vein drains into brachiocephalic vein

9. Explain the uses of central venous lines and indicate the landmarks for insertion of a central line into the internal jugular vein Uses of central lines Monitoring central venous pressure (CVP) in the right atrium, central venous saturations Central venous access for delivery of certain drugs, large amounts of intravenous medication, and central feeding Internal jugular vein (IJV) The right internal jugular is preferred as is it is normally larger and straighter The puncture site is found by palpating the common carotid artery and inserting the needle into the IJV just lateral to it at a 30° angle, aiming at the apex of the triangle between the sternal and clavicular heads of the SCM The needle is then directed inferolaterally towards the ipsilateral nipple.

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine 10. List the possible complications of insertion of central venous lines Arterial puncture leading to haematoma and potential airway obstruction Pneumothorax Nerve damage Air embolism Thrombosis Misplacement Perforation of the great vessels and heart Infection

11. Describe the origin, course and function of the phrenic and spinal accessory nerves The spinal accessory nerve originates from neuronal cell bodies located in the cervical cord and caudal medulla Most are located in the spinal cord and ascend through the foramen magnum and exit the cranium through the jugular foramen They are branchiomotor in function and innervate the sternocleidomastoid and trapezius muscles in the neck and back

spinal

Phrenic nerve – origin is C3-C5 Its course is over the anterior scalene muscle and enters the thorax between the subclavian artery and vein, and then down the mediastinum and over the lung hilus between the pleura and pericardium The right phrenic nerve passes close to the inferior vena cavae and the central tendon, whilst the left phrenic passes through the diaphragmatic muscle Its function is motor to the diaphragm and sensory to the diaphragmatic pleura and peritoneum

Biting, Chewing and Swallowing 1. Outline the main neuromuscular systems involved in biting, chewing, salivation and swallowing The muscles of mastication Masseter: o Supplied by mandibular branch of trigeminal (V) o Zygomatic arch to lateral surface of ramus and angle of mandible o Elevates mandible for forced closure of mouth Temporalis: o Mandibular branch of trigeminal (V) o Temporal fossa to coronoid process of mandible o Elevates and retracts mandible (posterior fibres) Medial Pterygoid: o Mandibular branch of trigeminal (V) o Lateral pterygoid plate/maxilla/palate of angle of mandible o Elevates, protracts and lateral movement of mandible for fast chewing Lateral Pterygoid: o Mandibular branch of trigeminal (V) o Sphenoid /lateral pterygoid process to neck of mandible o Depresses and protracts mandible to open mouth (mainly gravity) Buccinator o Supplied by the facial nerve (VII) o Cheek muscle and aids mastication by pressing the cheeks against the molar teeth when chewing – keeps food in occlusal plane The suprahyoid and infrahyoid muscles o Primarily used to raise and depress the hyoid bone and larynx, respectively, during swallowing o Indirectly, they can also help to depress the mandible, especially when opening the mouth suddenly or against resistance. The facial nerve (VII) keeps the lips closed

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine Biting Biting and

and Chewing involves the opening closing the jaw Chewing requires

the protrusion and retrusion of the and lateral movements The lateral movements are produced pterygoid muscle of the opposite Mastication is

chin, by the temporal muscle of the same side as the jaw movement and the side to the jaw movement aided by the buccinator muscles which push the cheeks against the molar teeth when chewing

o Innervated by the Bolus into oropharynx o Palatoglossus o Cranial root of the accessory nerve (XI) or vagus (X) – sources differ Close off nasopharynx by raising soft palate Raise the larynx, closed off by epiglottis Peristaltic wave of constrictor muscles Relax cricopharyngeus, open oesophagus

Swallowing Elevation and retraction of the tongue o Styloglossus and intrinsic muscles of the tongue hypoglossal nerve (XII)

*Anatomy workbook – the tongue* Muscles (inervated by the hypoglossal XII): o Styloglossus – retracts and elevates during swallowing o Hyoglossus – depresses tongue o Genioglossus – protracts tongue o Intrinsic muscles Salivation The parotid gland is supplied by the glossopharyngeal (IX) and opens into the parotid duct which opens at the upper second molar The submandibular salivary gland is located beneath and medial to the angle of the mandible The submandibular duct passes forwards to open out either side of the frenulum of the tongue The sublingual salivary glands are scattered along the submandibular duct into which some of them open. Some open directly into the oral cavity Secretomotor impulses to both glands are supplied by presynaptic parasympathetic, secretomotor fibres conveyed from the facial nerve to the lingual nerve by the chorda tympani nerve, which synapse with postsynaptic neurons in the submandibular ganglion

2. Identify the major branches of the external carotid artery (superior thyroid, ascending pharyngeal, lingual, facial, posterior auricular, occipital, superficial temporal, maxillary) The internal carotid artery has no branches until it enters the skull The external carotid artery has many branches In order of ascending branch, they are: superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, superficial temporal, and the maxillary artery

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

3. Assess those functions of the trigeminal, facial, glossopharyngeal, vagus and hypoglossal nerves which relate to biting chewing and swallowing Cranial nerve Trigeminal (V)

Facial (VI)

Glossopharyngeal (IX)

Vagus (X)

Function Ophthalmic division (V1) supplies skin of the forehead, upper eyelids, nose midline, and the anterior surface of the eye, nasal mucosa and frontal sinus Maxillary division (V2) supplies the skin of the temple and face as inferior as the corners of the mouth, and also upper teeth, lip, gums, and palate Mandibular division (V3) supplies a strip of skin from the temple to the chin, the lower teeth, gums, lips, floor of the mouth, and the anterior two thirds of the tongue. Also, see muscles of mastication. Proprioception (coordinate movements) of the muscles of the face and taste of the anterior two thirds of the tongue. Also somatic motor to muscles of the face, scalp and neck, and parasympathetic to the lacrimal, sublingual, submandibular, nasal, and palatine glands. Somatic and taste sensation from posterior third of tongue and oropharynx, and proprioception of the swallowing muscles. Also motor to the stylopharyngeus muscle and parasympathetic to the parotid gland. Somatic sensation from larynx and also taste from small number of receptors in epiglottis and pharynx.

Test Test sensations of the face and mouth in response to touch, pain, temperature and muscle sense. See if they can chew.

Test their taste and ask them to smile, salivate or cry.

Test taste and sensation at back of tongue. Encourage the gag reflex and check ability to salivate. Test swallowing, coughing and voice production. Check taste

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

Hypoglossal (XII)

Also motor to muscles of throat and neck and parasympathetic to smooth muscle of the trachea and oesophagus Main function is as the only motor nerve of the tongue causing movement through speech and swallowing

Test chewing, speaking and swallowing. If the nerve is injured on one side only then the tongue will deviate towards the side of the lesion. Long term – muscle wasting

4. Demonstrate how the temporo-mandibular joint and muscles of mastication produce chewing movements The temporo-mandibular joint is divided into two separate synovial cavities by a fibrocartilaginous disc o The lower part of the joint allows mainly the hinge-like depression and elevation of the mandible o The upper part of the joint allows the head of the mandible to translocate forward (protrusion) onto the articular tubercle and backward (retraction) into the mandibular fossa. Opening the mouth involves both depression and protrusion The forward or protrusive movement allows greater depression of the mandible by preventing backward movement of the angle of the mandible into structures in the neck Side to side movements - sliding occurs unilaterally, the head of the contralateral mandible rotates on the inferior surface of the articular disc. Movements about the temporo-mandibular joint are all produced by the muscles of mastication

5. Demonstrate the routes by which the maxillary, mandibular, facial, glossopharyngeal, vagus and hypoglossal nerves leave the skull, and indicate the courses of the lingual and inferior alveolar nerves The mandibular nerve (V3) is the largest and most inferior branch of the trigeminal nerve and it exits through the foramen ovale o The lingual nerve arises from the mandibular nerve (including chorda tympani VII component). The lingual nerve lies anterior to the inferior alveolar nerve. It is sensory to the anterior two-thirds of the tongue, the floor of the mouth, and the lingual gingivae o The inferior alveolar nerve enters the mandibular foramen and passes through the mandibular canal forming the inferior dental plexus, which sends dental branches to all mandibular teeth on its side The maxillary nerve (V2) leaves through the foramen rotundum The facial nerve (VII) leaves through the internal acoustic meatus The glossopharyngeal nerve (IX) leaves through the jugular foramen The vagus (X) leaves through the jugular foramen

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine The hypoglossal (XII) leaves through the hypoglossal canal

6. Describe the relationship between the facial nerve and the parotid gland The parotid gland lies at the side of the face superficially (parotid swellings, i.e. mumps) The parotid duct emerges from the anterior border and passes forwards on the masseter, then turns medially and penetrates the buccinator and opens into the mouth opposite the second upper molar tooth Parasympathetic secretomotor impulses come from the glossopharyngeal (IX) – the lesser petrosal nerve The facial nerve emerges from the skull through the stylomastoid foramen in the temporal bone It enters the parotid gland (does not innervate it), continues superficially, and forms a complex and variable plexus Branches of VII emerge from the anterior margin in five groups: o Temporal – to frontal belly of occipitofrontalis o Zygomatic – to orbicularis oculi and upper face o Buccal – to buccinatorm orbicularis oris and mid face o Marginal mandibular – to orbicularis oris and the corner of the mouth o Cervical – to platysma As the nerve is superficial, it is easy to damage leading to facial palsy. The mandibular branch is particulary in danger as it passes just below the lower margin of the mandible Bell’s palsy = a lower motor lesion of the facial nerve – lesion of cell bodies or the nerve itself causing the muscles of the face to sag on the affected side

7. Identify the positions of the parotid and submandibular glands and the lymph nodes draining the oral and oropharyngeal structures Parotid The parotid gland is the largest of the three main salivary glands in the head and numerous structures pass through it It is anterior to and below the lower half of the ear, superficial, posterior, and deep to the ramus of the mandible It extends down to the lower border of the mandible and up to the zygomatic arch Posteriorly it covers the anterior part of the sternocleidomastoid muscle and continues anteriorly to halfway across the masseter muscle Submandibular Each submandibular gland lies along the body of the mandible, partly superior and partly inferior to the posterior half of the mandible, Partly superficial and partly deep to the mylohyoid muscle Lymph Drainage To the deep cervical nodes either directly or via the submandibular, retropharyngeal, submental or parotid nodes

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

Parotid Gland

Sub-lingual Gland

Sub-mandibular Gland

8. Identify the teeth in the living mouth and record them accurately; recognise characteristic dental patterns for children and adults Left Upper Right Upper Left Lower Right Lower • • • • •

Incisors 2 2 2 2

Canines 1 1 1 1

Premolars 2 2 2 2

Molars 3 3 3 3

In a full adult set there are 32 teeth, including wisdom teeth, or 28 without There are 20 teeth in a complete deciduous set (no premolars (8) or wisdom teeth (4)) The first deciduous teeth first come at 6-8 months and are complete by 20-24 months Permanent adult teeth start at 6 years and are complete by the early 20’s These ages can be used as milestones to assess general development

9. Be able to identify the following structures in the living mouth: hard and soft palate, uvula, faucial pillars, palatine tonsils, lingual papillae, parotid and submandibular papillae, sublingual glands, frenulum, genioglossal ridge Faucil pillars - a pair of curved ridges running down the soft palate Parotid papillae – small raised patch neer the 2nd upper molar – opening of parotid duct Submandibular papillae – felshy tag with a forked tip found as you run doen the low gums and mandibular symphysis – where the submandicular salivary ducts open Sublingual glands – bumpy bit on the lower lateral buccal floor (the lingual papillae) Frenulum - small fold of tissue that secures or restricts the motion of a mobile organ in the body o Oral tissue: Frenula of the mouth include the frenulum linguae under the tongue, the frenulum labii superioris inside the upper lip, the frenulum labii inferioris inside the lower lip, and the buccal frena which connect the cheeks to the gum Genioglossal ridge – a smooth, firm rounded ridge running along the midline of the floor of the mouth to the tongue formed by the genioglossus muscle

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

Palatopharangeal fold

Breathing, Palatine tonsil

Uvula

Palatoglossal fold

Voice

Posterior wall of oropharynx

and Hearing 1. List the mechanisms which protect the lungs and bronchi against aspiration of food and drink There are two main mechanisms which function when swallowing o Levator veli palatine - muscle elevates the soft palate during swallowing, pushing the soft palate against the wall of the pharynx, thereby preventing the passage of the food into the nasal cavity o When swallowing, a peristaltic wave of activity of the constrictor muscles of the pharynx raises the larynx which becomes closed off by the epiglottis Gag reflex Sneezing – see below Coughing – see below

2. Explain (in terms of sensory and motor pathways and muscle groups) the sneeze and cough reflexes SNEEZING COUGHING Inspiration Intrathoracic pressure raised (glottis closed, abdominal muscles contracted)

Soft palate depressed against tongue (palatopharyngeus/palatoglossus)

Soft palate raised and tensed against posterior wall of pharynx. (Levator veli palatini, tensor veli palatini, sup. constrictor)

Sudden abduction of vocal folds to release intrathoracic pressure through nose or mouth

Cough o o

Afferent - irritation of receptors in larynx and trachea (laryngeal branches of X – internal laryngeal) Efferent  Deep inspiration, phrenic nerves (C3-5) to diaphragm and intercostal nerves (T1-12)  Build up of pressure against closed glottis - recurrent laryngeal – posterior cricoarytenoid muscle  Forced exhalation with oropharyngeal isthmus open - soft palate is raised and tensed against the posterior wall of the pharynx using the levator veli palatini (innervated by the cranial part of the accessory nerve (CN XI)), tensor veli palatini (innervated by the medial pterygoid nerve which is a branch of the mandibular nerve (CN V)), and the superior constrictor muscles of the pharynx (innervated by the cranial part of the accessory nerve (CN XI))  Sudden abduction of vocal cords - air escapes through mouth

Sneeze

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine o o

Afferent - irritation of receptors in larynx and trachea (laryngeal branches of X – internal laryngeal) Efferent  Deep inspiration, phrenic nerves (C3-5) to diaphragm and intercostal nerves (T1-12)  Build up of pressure against closed glottis - recurrent laryngeal – posterior cricoarytenoid muscle  Forced exhalation with oropharyngeal isthmus closed - soft palate becomes depressed against the tongue using the palatopharyngeus and palatoglossus muscles, innervated by the cranial part of the accessory nerve (CN XI)  Sudden abduction of vocal cords - air escapes through nose

3. Demonstrate in dissected specimens the landmarks of the nasal cavities, nasopharynx and soft palate

Frontal and cribiform plates/bones Mucus glands and capillary plexus for warming and humidification

Vocal Fold with Vestibular Fold above

Hard palate – front of mouth and is formed by processes of the maxillae and palatine bones and is covered by mucous membrane Soft palate – is further back. It is a moveable fold of mucous membrane that tapers at the back of the mouth to form a fleshy hanging flap of tissue called the uvula The lowest part of the airway – the larynx is modified for the production of voice

4. Demonstrate in living subjects the body of the hyoid, the thyroid and cricoid cartilages, the cervical part of the trachea, and the thyroid isthmus These structures constitute the larynx The hyoid bone is located at the base line of the mandible and serves as a point of an attachment to some neck muscles Inferiorly is the thyroid cartilage (made from two lamina which meet to form the adam’s apple, and leave an open back) Then inferior to this is the cricoid cartilage (which is a complete ring that is thicker posteriorly). Below this are the cartilaginous tracheal rings Between each of the structures is a membrane - the thyrohyoid membrane and cricothyroid membrane The isthmus of the thyroid is located just inferior to the cricothyroid cartilage

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

Phonation is the vocal sounds created when air is forced between vocal cords The quadrangular membrane merges with the cricothyroid membrane and bulges to form the vestibular fold and the vocal fold (which flattens/bulges when talking to help shape sound) The pitch depends on relative position and tension in vocal folds by movement of arytenoid cartilages and cricothyroid joint The inferior horn of the thyroid cartilage is articulated by the cricothyroid muscle (external laryngeal nerve) which causes changes in tension of the vocal cords and so changes in pitch The arytenoid cartilage inserts into the vocal cord and can move them further up, together or twist them causing movement of the vocal folds/chord – further alterations to pitch (recurrent laryngeal nerve) The intensity of a sound depends on force with which air is pushed through the glottis The quality of sound depends on resonation in the pharynx, mouth, and paranasal sinuses Words depend on shaping of sound with the mouth, particularly the tongue and lips

5. Demonstrate in living subjects and imaging the positions of the paranasal sinuses; define their sensory nerve supply; explain the clinical significance of their drainage routes The paranasal sinuses reduce the weight of the facial skeleton Act as resonators for the voice Are lined with respiratory epithelium and may become infected Are connected to the pharynx by small holes and therefore are a route of infection – build up of mucus in sinuses causes pain which doesn’t always clear easily.

Frontal sinuses – located in the frontal bone above the nose and terminate laterally in

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine the mid-orbital plane o The frontal sinuses drain into the frontonasal duct into the infundibulum, which opens into the semilunar hiatus of the middle meatus o Innervated by branches of the supraorbital nerves (arise from the trigeminal nerve). Ethmoidal sinus – comprised of several cavities known as ethmoidal air cells. These are located in the ethmoid bone behind the nose o The anterior and middle ethmoidal cells drain directly into the middle meatus through the infundibulum o The posterior ethmoidal cells open directly into the superior meatus. o Innervated by the nasocilliary nerves (CN V1), which is a branch of the trigeminal nerve. Maxillary sinus – these are in the maxilla, behind the cheeks, just lateral to the nose extending between the inferior border of the orbit and the upper lip o This sinus does not drain particularly well as the exit to the nasal cavity is 2/3 of the way up its medial border, and so has to fill before it actually drains anything o There is also a thin layer of bone between the sinus and the teeth and so a tooth infection can infect the sinus as well o Each maxillary sinus drains by an opening, called the maxillary ostium, into the middle meatus of the nasal cavity o Innervation of the maxillary sinus is via the anterior, middle, and posterior superior alveolar nerves. They are all branches of the maxillary nerve (arises from 2nd branch of the trigeminal nerve (CN V2)). Sphenoidal sinus – this is located just posterior to the ethmoidal air cells in the sphenoid bone o This is located in close proximity to the pituitary gland, and so can be utilised when operating on the pituitary (transphenoidal surgery) o The sphenoidal sinus is also in close proximity to the optic nerves, the optic chiasm, the internal carotid arteries, and the cavernous sinuses o These sinuses are innervated by the posterior ethmoidal nerve (a branch of the trigeminal nerve (CN V))

6. Explain the importance of the relationship of the maxillary sinus to the roots of the upper teeth, and of the sphenoid sinus to the pituitary fossa The maxillary sinus has the roots of teeth directly underneath and so abscesses/infection of the teeth can spread to the maxillary sinus o Because the superior alveolar nerves supply both the maxillary teeth and the mucous membrane of the maxillary sinus, inflammation of the mucosa of the sinus is frequently accompanied by a sensation of toothache in the molar teeth, especially when the maxilla is very thin in the floor of this sinus The sphenoid sinus provides a route of surgical entry through the nose for pituitary surgery

7. Explain pressure equalisation between the pharynx and the middle ear The pharyngotympanic tube (or auditory tube) connects the tympanic cavity to the nasopharynx, where it opens posterior to the inferior meatus of the nasal cavity The tube is tonically closed by a sphincter at its medial end, but during swallowing and yawning, it opens so that air can leave or enter the middle ear and equalise pressure with the nasopharynx and thus the atmosphere It is also a possible route of infection from the pharynx to the middle ear/mastoid air cells

8. Explain the clinical importance of the relationship of the mastoid antrum and air cells to the middle ear cavity in the skull

the mastoid

Mastoid air cells are located in the mastoid protcess They are connected via mastoid antrum to the tympanic cavity of the middle ear which in turn is connected to the pharynx via the auditory tube The pharyngotympanic tube can act as a route for infection from the pharynx to either the middle ear or the mastoid air cells (where there are tiny air filled compartments). Infections of the mastoid antrum and mastoid cells (mastoiditis) result from a middle ear infection that causes inflammation of the mastoid process Untreated, this can lead to temporal bone erosion The air cells are also close to the base of the brain where the bone can sometimes be incomplete giving a route for meningitis spread Infection can also spread to the sigmoid sinus via the internal jugular giving risk of thromboses

9. Identify the features of the external auditory meatus and eardrum that can be seen through an auroscope

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

If the cone of light is present then this indicates the ear is normal If infection is present in the middle ear then the cone of light reflection if lost

10. Outline the contributions of the structures and spaces of the airway and oral cavity to voice production See above

11. List the actions that may be taken to restore patency of the airway in an emergency Chin lift or jaw thrust (this straightens the airway, and opens up the airways making it easier for the patient to breathe of their own accord) Oropharyngeal or nasopharyngeal airway Endotracheal intubation – this is where an intubation tube is forced down the trachea, through the vocal cords, into the main bronchus of the lungs. Once this is done, the patient can be bagged, and therefore his breathing controlled Cricothyroidotomy (see the next learning objective) Tracheostomy (see the next learning objective)

12. Describe the anatomical basis of tracheotomy and cricothyroidotomy Cricothyroidotomy – would be done through the cricothyroid membrane in the midline, between the thyroid cartilage above and the cricoid cartilage below o Needle cricothyroidotomy – a large-bore intravenous cannula is inserted directly through the membrane. o Surgical cricothyroidotomy – a surgical hole is made in the cricothyroid membrane, and a cuffed tube, similar to a short endotracheal tube is inserted directly. This method affords much better airway protection Tracheostomy – a more permanent procedure. The infrahyoid muscles are retracted laterally, the isthmus of the thyroid gland is divided (much lower than a cricothyroidotomy) and an opening is made in the trachea between the 1 st and 2nd tracheal rings, or through the 2nd through 4th rings. A tracheostomy tube is then inserted and secured with neck straps

13. Explain likely consequences of disease or injury of a recurrent laryngeal nerve and of the superior part of the cervical sympathetic chain Any one of the following effects can occur during surgery – perhaps the worst effect being if the recurrent laryngeal nerve is damaged, as this will cause complete loss of voice

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine

With superior thyroid artery

With inferior thyroid artery LEFT: bronchial or oesophageal tumour/swollen mediastinal lymph nodes

*Further Information covered in lecture* Facial Nerve Has 3 functional components: o Motor – muscles of facial expression o Sensory – branches to the cauda tympani where it joins the linguinal nerve (a branch of the mandibular branch of the trigeminal) just after the acoustic meatus. Sensory to anterior 2/3 of tongue o Parasympathetic secretor motor – salivary (not parotid) and lacrimal glands via the submandibular, and pterygopalantine ganglia Leaves the brain stem at the junction of the pons and medulla via the internal acoustic meatus The stylomastoid foramen is a hole between the mastoid and styloid processes of the temporal bone The nucleus solitarius receives input from the taste buds and synapses with rely neurones to send information to the brainstem Bells Palsy – inflammation of the boney canal causes pressure on nerve which causes facial paralysis on one side. In 80% of cases nerve regenerates after treatment Depending on how high up the inflammation is will depend on which branches it affects and how much is affected

The Eye and Sight 1. Describe briefly the margin and walls of the bony orbit and name its important contents The orbit is a pyramidal, bony cavity in the facial skeleton with its base anterior and its apex posterior The bony orbit contains the visual apparatus together with nerves, vessels and lacrimal apparatus that maintain it, the muscles that move it and the orbital fat pad that cushions it

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine The bones forming the orbit are lined with periorbita (periosteum of the forms the facial sheath of the eyeball

orbit), which

Roof (superior wall) Orbital plate of frontal bone o Small contribution from the lesser wing of the sphenoid posteriorly Medial Wall Frontal process of maxilla Lacrimal Orbital plate of ethmoid o Small contribution from the lesser wing of the sphenoid Floor (inferior wall) Orbital surface of the maxilla o Small contribution from zygomatic and palatine bones Lateral Wall Zygomatic (anteriorly) Greater wing of sphenoid (posteriorly)

2. Identify on a skull the superior orbital fissure and the optic and name the nerves and vessels passing through them

canal

Optic canal o Optic nerve (II) o Ophthalmic artery Superior orbital fissure o Oculomotor (III), Trochlear (IV), Ophthalmic nerve (V1), Abducens (VI) o Ophthalmic vessels o Sympathetic fibres Inferior orbital fissure o Maxillary nerve (V2) o Infraorbital vessels

3. Identify the rectus and oblique muscles, levator palpebrae superioris and orbicularis oculi in suitable specimens

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine Note the axis of explain

the eyeball the action of muscles.

compared to the axis of orbit. This helps to the attached

Extrinsic muscles of eyeball o Four rectus muscles – superior,

o o

inferior, medial Two oblique Levator

and lateral muscles – superior and inferior plapebrae superioris - above the superior

the

rectus and below

the frontal bone. It acts to elevate the upper eyelid and acts with the superior rectus (i.e. when you look up) Orbicularis oculi – consists of two parts o orbital part - surrounds the orbit – tightly closes o palpebral part - which is in the eyelids – gently closes

4. Test the function of the following cranial nerves: oculomotor, trochlear, abducens, ophthalmic division of trigeminal, facial (to orbicularis oculi) Superior Rectus (III - occulomotor) Inferior Rectus (III) Lateral Rectus (VI - abucens) Medial Rectus (III) Inferior Oblique (III) Superior Oblique (IV – trochlear)

The series of movements aim to isolate the function of and test the specific supplying it

muscle/nerve

Levator Palpebrae Superioris (III) and sympathetic innervation o Sympathetic loss – partial ptosis (Horner’s Syndrome) o Occulomotor loss – complete ptosis Orbicularis Oculi (VII – facial) o Tested by closing the patient’s eye(s) tightly and asking the patient to resist your attempt to open them The ophthalmic nerve (a sensory nerve) - first branch of the trigeminal nerve (CN V1) o Can be tested by light touch, pin prick, and temperature over the forehead region o A partial loss can be diagnosed by comparing the response to the same stimulus on the other side

5. Explain the clinical significance of the close relationship between the superior orbital fissure and the cavernous sinus The superior ophthalmic veins drain into the cavernous sinus through the superior orbital fissure, providing a potential route for the spread of infection from around the orbit, nasal sinuses and superior part of the face This can lead to a cavernous sinus thrombosis and subsequent impairment of all the structures passing through it (lacrimal and frontal nerve (branches of ophthalmic division of trigeminal), trochlear nerve, occulomotor nerve and abducens

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine 6. Describe briefly the arterial supply and venous drainage of the eye, including the retina The orbit is supplied almost exclusively by the ophthalmic artery (a branch of the internal off immediately after it leaves the cavernous sinus). It has many braches: o Lacrimal artery → anterior ciliary branch o Central retinal artery o Posterior ciliary arteries o Muscular arteries (intrinsic of eyeball) o Supra-orbital arteries(forehead and scalp) o Ethmoidal arteries (ethmoidal air cells) o Palpebral arteries (medial eyelids) o Dorsal nasal arties (upper nose surface) o Supratrochlear (forehead) Superior and inferior ophthalmic vein o Superior → superior orbital fissue → cavernous sinus o Inferior is smaller → leaves by  Joining superior ophthalmic vein;  Draining through superior orbital fissure on its own; or  Passing through inferior orbital fissure to join with pterygoid

carotid – given

plexus

7. Understand how to test corneal and consensual light reflexes and explain the afferent and efferent components of these This diagram shows the corneal or pupillary light reflex Retinal photoreceptors detect the light, and the optic nerve (CN II (sensory)) transmits a signal to the pretectal nucleus At this stage, a motor signal is transmitted along the oculomotor nerves (CN III (motor)) to the ciliary ganglia This causes parasympathetic innervation of the pupillary sphincter which causes constriction of the pupil This response is a consensual reflex – that is both pupils constrict, even if only exposed to the light The patient is asked to look at a distant object The light is slowly shone into the left eye for a few seconds. In this time, you must observe the pupillary response of both eyes In normal people, the pupil will constrict in both eyes (perhaps more in the eye that the light is shone in to (so in this case the left eye)), but there will be a notable change in the size of the other pupil (of the right eye) This procedure will therefore be testing the optic nerve of the left eye, and the oculomotor nerves of both eyes. You then need to test the optic nerve of the other eye (in this case the right eye). this time is shone into the right eye, and again the responses of both pupils is Again, in a normal person, both pupils should constrict.

one eye is

So the light observed.

There is also something called afferent pupil defect test, or the swinging light test. Here the light is initially shone into one eye for a few seconds, and is then switched to the other eye, and then this cycle is repeated several times If any of the two optic nerves or two oculomotor nerves are slightly damaged, there will be a lagging of one or both eyes

8. Identify the optical and neural parts of the eye The parts of the eye can be divided into three main categories The muscles of the eye (already described) The optical structures of the eye The nervous supply of the eye Optical structures of the eye The cornea The iris and pupil The lens and ciliary muscles associated with it (for accommodation) The optic retina

Jack Roberts – 2nd Year Revision Notes 2008-09 – LCRS – Anatomy of the Head, Neck and Spine The yellow spot (fovea), which is technically known as the macula lutea Nervous supply to the eye In addition to the optic nerve, the nerves of the orbit include those that enter the through the superior orbital fissure and supply the ocular muscles o CN III supplies the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique. o CN IV supplies the superior oblique. o CN VI supplies the lateral rectus. Several branches of the ophthalmic nerve (CN V1) pass through the superior orbital fissure and supply structures in the orbit o The lacrimal nerve arises in the lateral wall of the cavernous sinus and passes to the lacrimal gland, giving branches to the conjunctiva and skin of the superior eyelid and providing secretomotor fibres conveyed to it from the zygomatic nerve (CN V2) o The frontal nerve divides into the supraorbital nerve and supratrochlear nerve, which supply the upper eyelid, forehead, and scalp. o The nasociliary nerve, the sensory nerve to the eye, supplies several branches to the orbit.  The infratrochlear nerve, a terminal branch of the nasociliary nerve, supplies the eyelids, conjunctiva, skin of the nose, and lacrimal sac  The ethmoidal nerves, also branches of the nasociliary nerve, supply the mucous membrane of the sphenoidal and ethmoidal sinuses and the nasal cavities, and the dura of the anterior cranial fossa  The short ciliary nerves, branches of the ciliary ganglion, carry parasympathetic and sympathetic fibres to the ciliary body and the iris (III). The long ciliary nerves, branches of the nasociliary nerves (CN V1), transmit postsynaptic sympathetic fibres to the dilator pupillae and afferent fibres from the iris and cornea. *See Grays Anatomy diagrams – too many/complex to include*

9. Outline the mechanisms of tear secretion, tear-film maintenance and tear drainage The lacrimal gland is a small exocrine gland in the upper part of the orbit Arranged around the anterior portion of levator palpebrae superioris – divided into two parts Secretomotor fibers from the parasympathetic part of the autonomic division of the PNS stimulate fluid secretion from the lacrimal gland. These preganglionic parasympathetic neurons leave the CNS in the facial nerve [VII], enter the greater petrosal nerve (a branch of the facial nerve [VII]), and continue with this nerve until it becomes the nerve of the pterygoid canal The nerve of the pterygoid canal eventually enters the pterygopalatine ganglion where the preganglionic parasympathetic neurons synapse on postganglionic parasympathetic neurons. The postganglionic neurons join the maxillary nerve [V2] and continue with it until the zygomatic nerve branches from it, and travel with the zygomatic nerve until it gives off the zygomaticotemporal nerve, which eventually distributes postganglionic parasympathetic fibers in a small branch that joins the lacrimal nerve (branch of V 1) . The lacrimal nerve passes to the lacrimal gland Numerous ducts open into the conjunctival sac, tears lubricating and protecting the eyeball, creating a tear film Tears then pass medially over the surface of the eyeball to the lacrimal lake, then into the lacrimal canaliculi via the puncta They drain into the lacrimal sac, then through the nasolacrinal duct into the inferior meatus of the nasal cavity Infection of the lacrimal canaliculi or ducts may block tears leading to dripping down cheeks. Excessive production has the same effect