Pa Part 1 Propede Pr edeuticss off Inte nal Medici Internal M dicine
Propede opedeut uticss of Internall Medicine Inte Partt 1 Pa
SPECIAL PART Chapter 3. RESPIRATORY SYSTEM FUNCTIONAL AND CLINICAL ANATOMy The respiratory organs consist of the upper respiratory tract: which includes the nose, pharynx, larynx, and the lower respiratory tract – trachea, bronchi, and lungs (Fig. 3.1).
Nostril
Sinus
Nasal cavity Hard palate Soft palate
Oral cavity
Pharynx Epiglottis
Larynx Trachea Bronchus
Left lung Right lung
Fig. 3.1. Respiratory organs
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The nose consist of the external nose – the projection on the face with two openings (nostrils or anterior nares) – and the nasal cavity, which is the internal part which is divided into right and left halves by the nasal septum. Each half of the nasal cavity communicates with the paranasal air sinuses via small opening, and by a large opening at the back (the posterior naris or choana) with the pharynx. The pharynx is a muscular tube about 12 cm long, which extends down from the base of the skull, consisting of nasal (the nasopharynx), oral (the oropharynx), and laryngeal parts (the laryngopharynx). The nasal part, into which the nasal cavities open, belongs exclusively to the respiratory tract, but the oral and laryngeal parts, commonly called the throat, belong to both the respiratory and alimentary tracts. At its lower end, the laryngopharynx opens into two structures: the larynx anteriorly, and the oesophagus directly below. The larynx, which is the organ of speech, opens from the front of the laryngopharynx and contains the vocal folds (or vocal cords) whose movements produce sounds. At the level of C6 vertebra, the lower end of the larynx continues into trachea (windpipe), which passes from the neck into the upper thorax. It is muscular tube about 10 cm long, which contain U-shaped strips of cartilage (called “rings”), which keep lumen continuously open. Just below the level of T4 vertebra, the trachea divides into the right and left main or principal bronchi, which enter the lungs. The left lung is divided into two lobes (upper and lower) by an oblique fissure, and is somewhat smaller than the right lung because the heart bulges towards the left. The right lung is divided into three lobes (upper, middle, and lower) by oblique and transverse fissures. Within the lungs, the main bronchi divide to form lobar bronchi, one for each lobe, and each in turn divides into segmental bronchi. Further subdivision results in a profusion of smaller tubes (bronchioles) that eventually open into the microscopically small air sacs (alveoli) through whose thin walls gaseous exchange can occur with the plasma and red cells of the blood in adjacent capillaries (Fig. 3.2). Due to its extensive branching pattern, the system of bronchi and bronchioles within each lung is often referred to as the bronchial tree.
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Venule
Bronchiole
Alveoli
Capillaries
Fig. 3.2. Diagrammatic representation of bronchioles, alveoli and blood capillaries
Topographic regions and lines of the chest. To describe an abnormality on the chest, you need to locate it in two dimensions: along vertical axis and around the circumference of the chest. To locate vertically, you must be able to number the ribs and interspaces accurately (Fig. 3.3). Note that an interspace between two ribs is numbered by the rib above it. As the 1st rib is covered by clavicle, the 1st interspace is below it. From here, using two fingers, you can “walk down the interspaces�. Do not try to count interspaces along the lower edge of the sternum; the ribs here are too close together. Note that the costal cartilages of only the first seven ribs articulate with the sternum. Those of the 8th, 9th, and 10th ribs articulate in-
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Manubrium of sternum Sternal angle
Body of sternum
1st rib st
1 interspace 2 2
3
3
4
4 5
Xiphoid process
5
6
6
Epigastric angle
Fig. 3.3. Anatomy of the chest wall. Anterior view
stead with the costal cartilages just above them. The 11th and 12th ribs, the so-called floating ribs, have no anterior attachments. The cartilaginous tip of the 11th rib can usually be felt laterally, and the 12th rib may be felt posteriorly. Costal cartilages are not distinguishable from ribs by palpation. When estimating location posteriorly, remember that the inferior angle of the scapula usually lies at the level of the 7th rib or interspace (Fig. 3.4).
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Spinous processes of C7
Spinous processes of T1
Inferior angle of scapula 7th interspace 7th rib
Fig. 3.4. Anatomy of the chest wall. Posterior view
Findings may also be located according to their relationship to the spinous processes of the vertebrae. When a patient flexes the neck forward, the prominent process is usually that of the 7th cervical. When two processes equally prominent, they are the 7th cervical and 1st thoracic. The processes below them can often be felt and counted, especially when the spine is flexed. The 12th rib gives you another possible starting point for counting the ribs and interspaces. This is especially useful in locating findings on the lower posterior chest.
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To locate findings around the circumference of the chest, use a topographic vertical lines. The median (or midsternal) and vertebral lines are precise; the others are estimated. The midclavicular line drops vertically from the midpoint of the clavicle. To find it, you must identify both ends of the clavicle accurately (Fig. 3.5).
1
2
3
4
Fig. 3.5. Topographic lines. Anterior view. 1 – median line, 2 – left parasternal line, 3 – left midclavicular line, 4 – left anterior axillary line
The anterior and posterior axillary lines drop vertically from the anterior and posterior axillary folds (the muscles that border the axilla). The midaxillary line drops from the apex of axilla (Fig. 3.6).
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2
1
3
Fig. 3.6. Topographic lines. Right anterior oblique view. 1 – midaxillary line, 2 – anterior axillary line, 3 – posterior axillary line
Posteriorly, the vertebral line follows the spinal processes of the vertebra. Paraspinal lines drop along vertebra; each scapular line drops from the inferior angle of the scapular (Fig. 3.7).
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2
1
Fig. 3.7. Topographic lines. Posterior view. 1 – vertebral line, 2 – paraspinal line, 3 – scapular line
The lungs lobes and fissures can be outlined mentally on the chest wall. Anteriorly, the apex of the each lung rises about 2 cm to 4 cm above the inner third of the clavicle (Fig. 3.8). The lower border of the lung passes the 6th rib at the midclavicular line and 8th rib at the midaxillary line. Posteriorly, the lower border of the lung lies at about the level of the 11th thoracic spinous process at the paraspinal line. On inspiration it descends (Fig. 3.9).
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Apex of the lung
Upper lobe of left lung
Upper lobe of right lung Middle lobe
Lower lobe of left lung
Lower lobe of right lung
Fig. 3.8. Projection of the lungs on the chest wall. Anterior view
You should usually locate your pulmonary findings in external terms, such as these: • Supraclavicular region – above clavicles; • Infraclavicular region – below clavicle; • Suprascapular region – above scapulae; • Interscapular region – between the scapulae; • Infrascapular region – below scapular; • Bases of the lungs – the lowermost points; • Upper, middle, and lower lungs fields.
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Left upper lobe
Left lower lobe
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Right upper lobe
Right lower lobe
Inspiratory descent
Fig. 3.9. Projection of the lungs on the chest wall. Posterior view
The pleurae are serous membranes that cover the outer surface of each lung (visceral pleura) and also line the inner thorax and upper surface of the diaphragm (parietal pleura). Their smooth opposing surfaces, lubricated by pleural fluid, allow the lungs to move easily within the thorax during inspiration and expiration. The pleural space is the potential space between visceral and parietal pleura.
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METHODS OF EXAMINATION Inquiry The main complaints of the patients with disease of the respiratory system are: dyspnea (breathlessness), cough, and chest pain. Dyspnea is determined as an abnormally uncomfortable awareness of breathing. Patients use a large variety of verbal expressions to describe these uncomfortable sensations, such as ‘breathlessness’, ‘short of breath’, ‘out of breath’, ‘cannot get enough air’, ‘air does not go all the way down’, ‘smothering feeling or tightness or tiredness in the chest’, a ‘choking sensation’, or even more colloquially ‘puffed’. The clinical analysis of dyspnea. All normal subjects will have experienced dyspnea on heavy exertion – physiological dyspnea. Pathological dyspnea is the same sensation occurring at lower workloads or at rest, and includes a perception that the awarness of breathing is unpleasant and/or inappropriate to the situation. The gradation of dyspnea may usefully be based on the amount of physical exertion required to produce the sensation. In assessing the severity of dyspnea, it is important to obtain a clear understanding of the patient’s general physical condition, work history, and recreational habits. For example, the development of dyspnea in a trained runner upon running 3 km may signify a much more serious disturbance than a similar degree of breathlessness in a sedentary person upon running a fraction of this distance. Dyspnea in its manifestation can be subjective, objective, and mixed. By subjective dyspnea is understood the subjective feeling of difficult breathing. Objective dyspnea is characterized by changes in respiration rate, depth, or rhythm, and also the duration of inspiration and expiration. Respiratory diseases are often accompanied by mixed dyspnea. Dyspnea is possible with normal, rapid breathing (tachypnea), and slow rate of breathing (bradypnea). Breathlessness is difficult to describe. Most patients can go no further than saying that they are ‘short of breath’. Three types of dyspnea quality are differentiated by the prevalent breathing phase: inspiratory dyspnea (more difficult to breath in than out), expiratory dyspnea (more difficult to breath out than in), and mixed dyspnea when both inspiration and expiration phases become difficult.