HUMAN ANATOMY – VOLUME 1

The rima glottidis is dilated by the p o s t e r i o r c r i c o a r y t e n o i d m u s c l e. This muscle originates from the back of the cricoid cartilage plate, extends upward and laterally and is inserted into the muscular process of the arytenoid cartilage. During contraction it pulls the muscular process backwards, turning the arytenoid cartilage to the outside. The vocal process moves laterally, widening the rima glottidis.

C o n s t r i c t o r s o f the r i m a g l o t t i d i s include the lateral cricoarytenoid, thyroarytenoid, transverse and oblique arytenoid muscles. The l a t e r a l c r i c o a r y t e n o i d m u s c l e originates on the lateral part of the cricoid cartilage arch. It extends upward and to the back, and attaches to the muscular process of the arytenoid cartilage. During its contraction the muscular process moves forward, while the vocal process shifts inwardly, narrowing the rima glottidis (especially its anterior section). The t h y r o a r y t e n o i d m u s c l e originates from the inner surface of the thyroid cartilage, extends upward and to the back, and inserts on the muscular process of the arytenoid cartilage. These muscles also pull the muscular process forward, bringing the vocal processes together and closing the vocal fissure. The t r a n s v e r s e a r y t e n o i d m u s c l e is situated on the posterior surface of the two arytenoid cartilages. During contraction it brings these two cartilages closer, narrowing the posterior section of the rima glottidis. The o b l i q u e a r y t e n o i d m u s c l e passes in the form of separate fascicles from the posterior surface of the muscular process upward and medially to the lateral edge of the other arytenoid cartilage. Fascicles of the right and left oblique arytenoid muscles cross behind the transverse arytenoid muscle. During contraction they draw the arytenoid

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cartilages toward each other. Separate fascicles from these muscles continue inside the a r y e p i g l o t t i c f o l d and are inserted into the lateral edges of the epiglottis, forming the a r y e p i g l o t t i c m u s c l e. These fascicles narrow the laryngeal inlet. The aryepiglottic muscles bend back the epiglottis, closing the larynx, during the act of swallowing.

The v o c a l l i g a m e n t s a r e t e n s e d (s t r e t c h e d) by the cricothyroid and vocal muscles. The c r i c o t h y r o i d m u s c l e originates from the anterior surface of the cricoid cartilage arch. It has a s t r a i g h t and o b l i q u e p a r t s. The straight part inserts on the inferior margin of the thyroid cartilage, and the oblique part — on its inferior horn. These muscles cause movement in the cricothyroid joint, bending the thyroid cartilage forward. The distance between this cartilage and the vocal processes increases and the vocal ligaments become tensed. Returning of the thyroid cartilage into its initial position relaxes the vocal ligaments. The v o - c a l m u s c l e (i n t e r n a l t h y r o a r y t e n o i d m u s c l e) is situated inside the homonymous fold. It originates on the lateral surface of the vocal process of the arytenoid cartilage and is insered into the inner surface of the thyroid cartilage angle. Part of its fascicles weaves into the focal cord. This muscle can contract totally or by separate fascicles, thus stretching the entire vocal cord or only parts of it.

The larynx is formed by three layers, including mucosa, fibrocartilaginous layer and adventitia. The m u c o s a is lined primarily with stratified ciliary epithelium. Only the vocal cords are covered by stratified squamous epithelium. The lamina propria of mucosa is formed by loose connective tissue, and contains a lot of elastic fibers, which lie in no particular arrangement. These elastic fibers weave into the perichondrium. Inside the lamina propria lie numerous mixed glands. There is an especially high concentration of them in the region of the vestibule and ventricles of the larynx. In the region of the vocal ligaments glands are absent. The lamina propria also contains a lot of lymphoid formations. There are especially large accumulations of lymphoid tissue in the walls of the ventricles. The muscularis mucosa is almost undeveloped. The submucosa is thickened by a considerable content of fibrous and elastic fibers (f i b r o e l a s t i c m e m b r a n e). This fibroelastic membrane is divided into two parts called the q u a d r a n g u - l a r m e m b r a n e and the elastic cone. The q u a d r a n g u l a r m e m - b r a n e corresponds to the vestibule of the larynx. Its superior margin reaches the aryepiglottic folds. Its free lower margin forms, on each side, the vestibular ligament of the larynx. The right and left vestibular ligaments lie inside the homonymous folds. The e l a s t i c c o n e corresponds to the subvocal cavity region. Its free upper margin is thickened and stretched between the thyroid cartilage angle and the vocal processes, forming the vocal ligaments.

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The f i b r o c a r t i l a g i n o u s layer consists of the hyaline and elastic cartilages of the larynx. The epiglottis, cuneiform and corniculate cartilages and the vocal processes of arytenoid cartilages are elastic. The thyroid, cricoid and arytenoid cartilages are hyaline.

The a d v e n t i t i a of the larynx is formed by loose fibrous connective tissue.

Fig. 158. Position of vocal ligaments during various functional stages of larynx. Rima glottidis is closed(I), opened(II), and widelydilatated (III).

A — laryngoscpopic picture; 1 — epiglottis; 2 — epiglottic tubercle; 3 — vocal fold; 4 — corniculate tubercle; 5 — cuneiform tubercle; 6 — vestibular fold. B — scheme of various positions of vocal ligaments, rima glottidis and arytenoid cartilages; 1 — right lamina of thyroid cartilage; 2 — vocal fold; 3 — arytenoid cartilage; 4 — posterior cricoarytenoid muscle; 5 — lateral cricoarytenoid muscle; 6 — transverse arytenoid muscle; 7 — thyroarytenoid muscle.

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Oscillations of the vocal cords (folds), which are caused by the current of exhaled air, produce sound. The strength and pitch of this sound depend on the speed of the air current and the tension of the vocal cords (Fig. 158). Speech is formed with participation of the lips, tongue and palate. The cavity of the larynx and the paranasal sinuses serve as sound resonators.

I n n e r v a t i o n of the larynx: superior and inferior laryngeal nerves (from vagus nerve), laryngopharyngeal branches (from sympathetic trunk).

B l o o d s u p p l y: superior laryngeal artery (from superior thyroid artery), inferior laryngeal artery (from inferior thyroid artery).

Ve n o u s o u t f l o w: superior and inferior laryngeal veins (into internal jugular vein).

Ly m p h o u t f l o w: deep cervical lymph nodes (internal jugular and prelaryngeal nodes).

Questions for revision and examination

1.Name the cartilages of the external nose and their location.

2.Describe the structure of the lateral wall of the nasal cavity, the nasal conchae and nasal meatuses.

3.Describe the structure and functions of mucosa of the nasal cavity.

4.Name the cartilages of the larynx and the means by which they articulate with each

other.

5.Name the muscles which expand the vocal fissure and which contract it.

6.What muscles stretch the vocal cords? Describe the mechanism of this function.

7.Describe the inner surface of mucosa of the larynx. Explain what is the fibroelastic membrane of the larynx.

TRACHEA

The trachea (trachéa) is a hollow tubular organ, which serves as a passage for air to and from the lungs. In an adult the trachea begins at the lower margin level of the sixth cervical vertebra, where it connects with the larynx, and ends at the upper margin level of the fifth thoracic vertebra. The trachea lies in the anterior part of the neck (its c e r v i c a l p a r t) and in the mediastinum of the thoracic cavity (its t h o r a c i c p a r t). In front of the cervical trachea (its upper region) lie the lower part of the thyroid gland, pretracheal lamina of the cervical fascia, and sternohyoid and sternothyroid muscles. Behind the trachea lies the esophagus. At its sides lies a paired neurovascular bundle, which contains the common carotid artery, internal jugular vein and vagus nerve. Inside the thoracic cavity to the front of the trachea lies the arch of aorta, brachiocephalic trunk, brachiocephalic veins, beginning of the left common carotid artery and thymus gland. Behind it lies the esophagus, and at the sides — the right

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and left mediastinal pleura. The average length of the trachea in an adult is 10–11 cm (ranges from 8.5 to 15 cm). At the level of the fifth thoracic vertebra the trachea divides into the right and left bronchi (tracheal bifurcation) (Fig. 159). Inside the lumen of the bifurcation region there is a semilunar prominence called the c a r i n a.

The wall of the trachea consists of a m u c o s a, s u b m u c o s a, f i - b r o c a r t i l a g i n o u s l a y e r and a d v e n t i t i a. The mucosa is lined with pseudostratified columnar epithelium, which lies on a basement mem-

Fig. 159. Trachea and bronchi of right and left lungs. Anterior aspect.

1 — oesophagus; 2 — trachea; 3 — aorta; 4 — left main bronchus; 5 — left pulmonary artery; 6 — left superior lobular bronchus; 7 — segmental bronchi; 8 — left inferior lobular bronchus; 9 — azygos vein; 10 — segmental bronchi of inferior and middle lobes of right lungs; 11 — right inferior lobular bronchus; 12 — right middle lobular bronchus; 13 — right superior lobular bronchus; 14 — right main bronchus; 15 — tracheal bifurcation.

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brane. Among its epitheliocytes are mostly ciliated cells, each of which may have up to 250 cilia. Movements of these cilia are directed upwards, toward the larynx. The epithelium contains a large number of goblet cells, which produce mucus. There are also basal (stem) cells, endocrinocytes (they secrete noradrenalin, serotonin, dopamine) and some other types of epitheliocytes. The lamina propria of mucosa contains a lot of longitudinally oriented elastic fibers and lymphoid tissue. Inside the lamina propria there are separate smooth myocytes with primarily circular orientation. The lamina propria mucosa is perforated by numerous excretory ducts of the glands, which lie inside the submucosa. The submucosa consists of loose fibrous connective tissue, and contains vessels, nerves and lymphoid nodules. The fibrocartilaginous layer is formed by 16–20 hyaline cartilages, connected by a n n u l a r l i g a m e n t s. Each cartilage is shaped like an arch, which occupies two thirds of the circumference of the trachea. The annular ligaments, which connect and cover them, pass into their perichondrium. The posterior membranous wall of the trachea is formed by dense fibrous connective tissue with fascicles of myocytes. On the outside the trachea is covered by adventitia.

MAIN BRONCHI

The right and left main bronchi (brónchi principáles) begin at the bifurcation of the trachea, at the upper edge level of the C5 vertebra. They extend to the hila of the right and left lung, where they divide into lobar bronchi. Above the l e f t m a i n b r o n c h u s lies the arch of the aorta; above the right bronchus — the azygos vein. The r i g h t m a i n b r o n - c h u s is situated more vertically and has a shorter length (approximately 3 cm) than the left (4–5 cm in length). The right main bronchus is also wider (1.6 cm in diameter) than the left bronchus (1.3 cm in diameter). The walls of the main bronchi have the same structure as the trachea. Their structure is base on arches of cartilage (6–8 in the right bronchus and 9–12 in the left).

I n n e r v a t i o n of trachea and bronchi: branches of recurrent laryngeal nerves and sympathetic trunk.

B l o o d s u p p l y: branches of the inferior thyroid artery, internal thoracic artery and thoracic part of aorta.

Ve n o u s o u t f l o w: into brachiocephalic veins.

Ly m p h o u t f l o w: lateral deep cervical (internal jugular) lymph nodes, pretracheal and paratracheal, superior and inferior tracheobronchial lymph nodes.

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LUNGS

The right and left lungs (pulmónes) are situated in the corresponding halves of the thorax, within the pleural cavities. Situated between the lungs are the organs of the mediastinum. At the front, back and sides each lung adjoins the internal surface of the thoracic cavity. The shape of a lung resembles a cone flattened on one side and with a rounded a p e x. The right lung is 25–27 cm long and 12–14 cm wide. It is 2–3 cm shorter and 3–4 cm narrower than the left lung, due to a higher location of the right cupola of the diaphragm. Each lung has three surfaces. The d i a - p h r a g m a t i c s u r f a c e is concave; it faces the diaphragm. The costal surface is convex and adjoins the inside of the thoracic wall. The vertebral part of this surface lies against the spine. The m e d i a l (m e d i a s t i n a l) s u r f a c e of the lung adjoins the mediastinum. Each lung has a base, which corresponds to the diaphragmatic surface, and an apex. The surfaces of the lung are limited by its margins. Between the c o s t a l and m e - d i a l s u r f a c e s is the a n t e r i o r b o r d e r, and between these surfaces and the diaphragmatic surface is the i n f e r i o r b o r d e r. On the anterior margin of the left lung is a recession called the c a r d i a c n o t c h, limited at the bottom by the lingula of the left lung.

The right and left lungs have somewhat different projections onto the skeleton. The apex of the right lung in the front projects 2 cm above the clavicle and 3–4 cm above the first rib. In the back it projects at the level of the C7 spinous process. The anterior margin of the right lung extends from its apex to the right sternoclavicular joint. Then it passes through the middle the sternal angle. It extends downward behind the sternum (slightly left of the median line) to the cartilage of rib 4, where it continues into the inferior margin. Along the midclavicular line the inferior margin of the right lung corresponds to rib 6; on the anterior axillary line — to rib 7; on the middle axillary line — to rib 8; on the posterior axillary line — rib 9; on the subscapular line — rib 10; and on the paravertebral line — neck of rib 11. At the level of the eleventh rib the inferior margin turns upward, continuing into the posterior margin, which extends up to the head of the second rib.

The apex of the left lung protrudes 2 cm above the clavicle. From the apex the anterior margin extends to the left sternoclavicular joint, and then behind the body of the sternum down to the cartilage of rib 4. Then the anterior margin of the left lung deviates to the left and extends along the lower edge of the fourth costal cartilage until the parasternal line. From there it extends down to the sixth costal cartilage and abruptly turns, con-

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tinuing into the inferior margin. The inferior margin of the left lung is situated approximately half a rib lower than that of the right lung. On the paravertebral line it continues into the posterior margin, which passes upward along the vertebral column. The posterior margins of the right and left lungs are approximately the same.

Each lung is divided into lobes by deep fissures. The right lung consists of three l o b e s (s u p e r i o r, m i d d l e and i n f e r i o r), and the left consists of two (s u p e r i o r and i n f e r i o r). In both lungs there is an oblique fissure, which extends from its posterior margin 6–7 cm below the apex (level of T3 spinous process) forward and down, to the anterior margin, where the later projects on the junction between rib 6 and its costal cartilage. From there the oblique fissure extends along the medial surface to the hilus of the lung. In both lungs the oblique fissure separates the inferior lobe. In the right lung there is also a horizontal fissure. It begins on the costal surface, approximately from the middle of the o b l i q u e f i s - s u r e , where the latter crosses the middle axillary line. It extends across

Fig. 160. Branching of bronchi of left and right lungs.

A — branching of bronchi within right and left lungs: 1 — trachea; 2 — main bronchi; 3 — lobular bronchi; 4 — segmental bronchi; 5 — lobule; 6 — acinus; 7 — inferior lobe of right lung; 8 — segment.

B — sequenced numeration of lobes: 1, 2 — main bronchi; 3, 4 — lobar and segmental bronchi; 5–15 — branches of segmental bronchi, lobular bronchi; 16 — terminal bronchiole; 17–19 — respiratory bronchioles; 20–22 — alveolar ducts; 23 — alveolar sacs.

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the lung to its anterior margin, where it turns and passes to its hilus. The h o r i z o n t a l f i s s u r e separates the middle and superior lobes. The middle lobe of the right lung can be seen only from the front and medial sides. The lobes of the liver adjoin each other with their interlobar surfaces. On the medial surface of each lung is t h e h i l u m, which contains the r o o t o f t h e l u n g, formed by vessels, nerves and the main bronchus. In the hilus of the right lung the main bronchus is situated at the top, below it the pulmonary artery, and at the bottom — two pulmonary veins. In the hilus of the left lung at the top lies the artery, below it — the main bronchus, and at the bottom lie the veins. In the right lung the hilus is somewhat shorter and wider than in the left one.

In region of the hilus the main bronchus divides into three l o b a r, or secondary, b r o n c h i (Fig. 160). When entering the superior lobe of the right lung the bronchus is situated above the lobar artery (branch of pulmonary artery), or epiarterially. In all other lobes of the right and left lungs the lobar bronchus lies beneath the lobar artery (hypoarterially). The lobar bronchi divide into smaller s e g m e n t a l (tertiary) b r o n c h i, which continue to divide dichotomically. Division of bronchi and their nomenclature are shown in table 19.

Table 19. Division of bronchi inside the lungs.

Each segmental bronchus spreads through a separate segment of a lung (Fig. 161, 162). The nomenclature of the lung segments corresponds to names of the segmental bronchi (see table 18). In the center of each segment lie the segmental bronchus and artery. The segmental veins pass through the connective tissue layers, which separate neighboring bronchi. The segmental bronchi divide into subsegmental branches (9–10 consecutive divisions), which then are devidedinto lobular and interlobular bronchi.

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Fig. 161. Right and left lung. Left lung is incised in frontal sectioned. Anterior aspect.

1 — right lung; 2 — apex of lung; 3 — larynx; 4 — trachea; 5 — left lung; 6 — superior lobe; 7 — main bronchus of left lung; 8 — inferior lobe; 9 — inferior margin; 10 — cardiac notch; 11 — medial margin of right lung; 12 — inferior lobe; 13 — oblique fissure; 14 — middle lobe; 15 — horisontal fissure; 16 — superior lobe of right lung.

The structure of bronchi is similar throughout the whole b r o n c h i a l t r e e. Their walls consist of m u c o s a, s u b m u c o s a, f i b r o c a r t i l a g - i n o u s l a y e r and a d v e n t i t i a. The mucosa is lined with ciliary epithelium. The thickness of epithelium decreases as the bronchi become smaller, and columnar epitheliocytes are gradually switched form columnar to cuboidal. In the beginning the walls of the small bronchi are lined with two-layer epithelium, which passes into simple. Among epitheliocytes there are goblet cells, endocrinocytes and basal cells. In distal sections of the bronchial tree there are also secretor secretory Clara cells, which produce enzymes that break down surfactant (see below). The lamina propria of mucosa contains a large amount of longitudinal elastic fibers, which make the bronchial wall resilient. Inside the lamina propria lie vessels, nerves and lymphoid tissue. The thickness of the lamina propria (relative to thickness of the bronchial wall) increases from large bronchi to small. Oblique and circular muscle fascicles of the muscularis mucosa promote the formation of mucosal folds. These folds are present, however, only in large bronchi, which are 5–15 mm in diameter. Aside from vessels, nerves and lymphoid tissue the submucosa contains secretory sections of

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