Human Anatomy and Physiology (with Age-Related Features of the Child's Body) - M.R. Sapin, V.I. Sivoglazov 2002

Splanchnology (Internal Organs)
Respiratory System
Airways

The respiratory Organs include the Nasal cavity, Pharynx, Larynx, Trachea, Bronchi, and Lungs (Fig. 49). All respiratory organs (except the lungs) are airways; they conduct air from the outside into the lungs and from the lungs back out. The lungs form the Respiratory Portion, as gas exchange between air and Blood takes place within them.

The airways have either a bony framework (nasal cavity) or Cartilage (larynx, trachea, bronchi) in their walls. Therefore, these organs maintain an open lumen and do not collapse. The mucous membrane of the airways is lined with ciliated epithelium, whose cellular cilia move to expel foreign particles that have entered the respiratory tract along with mucus.

Nasal cavity

The nasal cavity serves a dual function: it is the beginning of the respiratory tract and the Organ of Smell. As inhaled air passes through the nasal cavity, it is filtered, warmed, and humidified. Odorants present in the inhaled air stimulate olfactory receptors, generating Olfactory nerve impulses.

Class="center">

Fig. 49. Respiratory system (diagram):

1 — Oral Cavity, 2 — nasopharynx, 3 — soft palate, 4 — Tongue, 5 — oropharynx, 6 — epiglottis, 7 — laryngopharynx, 8 — larynx, 9 — Esophagus, 10 — trachea, 11 — apex of the lung, 12 — superior lobe of the left lung, 13 — left main bronchus, 14 — inferior lobe of the left lung, 15 — alveoli, 16 — right main bronchus, 17 — right lung, 18 — Hyoid bone, 19 — Mandible, 20 — Vestibule of the Mouth, 21 — oral fissure, 22 — hard palate, 23 — nasal cavity

Anteriorly, the nasal cavity is covered (and protected) by the External Nose. The dorsum of the nose, which has a bony framework, continues downward into its apex. The wings of the nose (its lateral parts) are reinforced by cartilaginous plates — the alar cartilages of the nose.

The nasal cavity is divided by a septum into right and left halves. The nasal septum is formed by the perpendicular plate of the Ethmoid bone and the Vomer. Posteriorly, the nasal cavity communicates with the upper part of the pharynx — the nasopharynx — through openings called choanae. On the lateral walls, there are three nasal conchae: superior, middle, and inferior, which hang into the nasal cavity. Between the conchae lie the nasal meatuses: superior, middle, and inferior (Fig. 50).

The olfactory receptors, which perceive various odors, are located in the mucous membrane covering the upper Regions of the nasal cavity (the superior nasal conchae and superior nasal meatuses). This part of the nasal cavity is called the olfactory region. The zone of the inferior and middle nasal meatuses is called the respiratory region.

The mucous membrane of the nasal cavity is rich in Blood Vessels (Veins), whose purpose is to warm the inhaled air. If the mucous membrane is irritated or damaged, nosebleeds easily occur here. The Paranasal Sinuses open into the nasal cavity: the frontal, maxillary (antrum of Highmore), sphenoid, and ethmoidal labyrinths. These air-filled paranasal sinuses not only reduce the weight (mass) of the Skull but also serve as resonators for sounds and the voice.

Fig. 50. Lateral wall of the nasal cavity:

1 — frontal sinus, 2 — middle nasal concha, 3 — superior nasal concha, 4 — Inferior nasal concha, 5 — sphenoid sinus, 6 — pharyngeal tonsil, 7 — pharyngeal opening of the auditory tube, 8 — hard palate

From the nasal cavity, inhaled air passes through the choanae into the nasopharynx. Then, passing through the oropharynx, where it crosses the digestive pathway, it enters the larynx. Air also enters the oropharynx during mouth breathing.

Age-related Features of the nasal cavity

In a newborn, the nasal cavity is low (its height is 17.5 mm) and narrow. The nasal conchae are relatively thick, and the nasal meatuses are poorly developed. The inferior nasal concha touches the floor of the nasal cavity. The common nasal meatus remains free, and the newborn breathes through it; the choanae are low. By 6 months, the height of the nasal cavity increases to 22 mm, and the middle nasal meatus is formed; by 2 years, the inferior meatus develops, and after 2 years, the superior one. By 10 years of age, the length of the nasal cavity increases 1.5 times, and by 20 years, it doubles compared to that of a newborn. Of the paranasal sinuses, only the maxillary sinus is present in a newborn, and it is poorly developed. The remaining sinuses begin to form after birth. The frontal sinus appears In the second year of life, the sphenoid sinus by 3 years, and the ethmoidal Cells by 3–6 years. By 8–9 years, the maxillary sinus occupies almost the entire body of the bone. By 5 years, the frontal sinus is the size of a pea. The size of the sphenoid sinus in a child of 6–8 years reaches 2–3 mm. At 7 years of age, the ethmoidal sinuses lie close to each other; by 14 years, their Structure resembles the ethmoidal cells of an adult.

Larynx

The larynx is located in the anterior part of the neck, below the hyoid bone, at the level of the IV—VI cervical vertebrae. In front of the larynx are the SUPERFICIAL Muscles OF the neck, and behind it is the laryngopharynx. The larynx is connected to the hyoid bone by Ligaments and Muscles. During swallowing, speaking, and coughing, the larynx moves up and down. Superiorly, the larynx communicates with the pharynx; inferiorly, it continues into the trachea. The Thyroid Gland lies anteriorly and laterally to the larynx.

The Skeleton of the larynx consists of cartilages connected to each other by joints and ligaments. These are the thyroid, cricoid, arytenoid cartilages, and the epiglottis (Fig. 51). The thyroid cartilage is the largest, consisting of two quadrangular plates joined anteriorly at a right angle. This angle projects forward, forming a prominence well-defined in men (the Adam's apple). Below the thyroid cartilage lies the cricoid cartilage, connected to the thyroid cartilage by two joints. Posteriorly, on the lamina of the cricoid cartilage, There are two mobile arytenoid cartilages, above which also lie paired miniature corniculate and cuneiform cartilages. The entrance to the larynx from the pharynx is closed by the elastic epiglottis. The inner surface of the larynx is lined with a mucous membrane.

Fig. 51. Cartilages, ligaments, and JOINTS OF THE larynx:

A — anterior view: 1 — body of the hyoid bone, 2 — triticeal cartilage, 3 — superior horn of the thyroid cartilage, 4 — lamina of the thyroid cartilage, 5 — inferior horn of the thyroid cartilage, 6 — arch of the cricoid cartilage, 7 — tracheal cartilages, 8 — anular ligaments, 9 — cricothyroid joint, 10 — cricothyroid ligament, 11 — superior thyroid notch, 12 — thyrohyoid membrane, 13 — median thyrohyoid ligament, 14 — lateral thyrohyoid ligament.

B — posterior view: 1 — epiglottis, 2 — greater horn of the hyoid bone, 3 — triticeal cartilage, 4 — superior horn of the thyroid cartilage, 5 — lamina of the thyroid cartilage, 6 — arytenoid cartilage, 7 — right cricoarytenoid joint, 8 — right cricothyroid joint, 9 — tracheal cartilages, 10 — membranous wall of the trachea, 11 — lamina of the cricoid cartilage, 12 — left cricothyroid joint, 13 — inferior horn of the thyroid cartilage, 14 — left cricoarytenoid joint, 15 — muscular process of the arytenoid cartilage, 16 — vocal process of the arytenoid cartilage, 17 — thyroepiglottic ligament, 18 — corniculate cartilage, 19 — lateral thyrohyoid ligament, 20 — thyrohyoid membrane

The laryngeal cavity is divided into three regions: superior, middle, and inferior (Fig. 52). The superior region, which narrows downward to the vestibular ligaments, is called the laryngeal vestibule. The middle region lies between the vestibular (false vocal) folds above and the vocal (true vocal) folds below. In this narrowest part of the larynx, foreign objects that enter the airways can become lodged. On the right and left sides, between the vestibular and vocal folds, there are depressions — the right and left laryngeal ventricles. The inferior region of the larynx — the infraglottic cavity — is located below the vocal folds. Widening downward, the infraglottic cavity continues into the trachea.

The vocal folds, covered by mucous membrane, are formed by the vocal ligaments and vocal muscles stretched between the thyroid cartilage anteriorly and the arytenoid cartilages posteriorly. The narrow sagittal space between the vocal folds is called the rima glottidis. As exhaled air passes through the rima glottidis, the vocal folds vibrate and produce sounds.

Fig. 52. Laryngeal cavity. Posterior view:

1 — greater horn of the hyoid bone, 2 — triticeal cartilage, 3 — thyrohyoid membrane, 4 — superior horn of the thyroid cartilage, 5 — vestibular fold, 6 — laryngeal ventricle, 7 — vocal fold, 8 — cricoarytenoid joint, 9 — infraglottic cavity, 10 — lamina of the cricoid cartilage (partially removed), 11 — posterior cricoarytenoid Muscle, 12 — arytenoid cartilage, 13 — corniculate cartilage, 14 — laryngeal vestibule, 15 — lateral thyrohyoid ligament, 16 — epiglottis

During quiet breathing, the width of the rima glottidis is 5 mm. During phonation, especially during singing or shouting, the rima glottidis widens to its maximum size of up to 15 mm (Fig. 53). The deeper pitch of the male voice is due to the greater length of the vocal folds compared to women and children. The tension of the vocal folds and the width of the rima glottidis during respiration and phonation are regulated by the laryngeal muscles. These include the vocalis and cricothyroid muscles, which tense the vocal folds, the lateral cricoarytenoid muscles (which narrow the rima glottidis), the posterior cricoarytenoid muscles (which widen the rima glottidis), and others. The Lips, tongue, Teeth, oral cavity, and nasal cavity with its paranasal sinuses also participate in The formation of articulate speech.

Age-related features of the larynx

The larynx of a newborn is relatively large; it is short, wide, funnel-shaped, and situated higher than in an adult (at the level of the II—IV vertebrae). The laminae of the thyroid cartilage lie at an obtuse angle to each other. The laryngeal prominence is absent. Due to the high position of the larynx in newborns and infants, the epiglottis is located slightly above the ROOT of the tongue; therefore, during swallowing, the food bolus (or liquid) bypasses the epiglottis laterally. As a result, the child can breathe and swallow (drink) simultaneously, which is crucial for the act of sucking,

The laryngeal inlet in a newborn is relatively wider than in an adult. The vestibule is short, so the rima glottidis is located high and has a length of 6.5 mm (3 times shorter than in an adult). The rima glottidis increases significantly During the first three years of a child's life and then during Puberty. The laryngeal muscles in newborns and children are poorly developed. Their most intensive growth is observed during puberty. The larynx grows rapidly during the first four years of life. During puberty (after 10—12 years), active growth resumes, continuing until age 25 in men and 22—23 in women. Along with the growth of the larynx (which gradually descends) in childhood, the distance between its upper margin and the hyoid bone increases. By age 7, the lower margin of the larynx is at the level of the upper margin of the VI cervical vertebra. The larynx assumes the position characteristic of an adult after 17—20 years.

Fig. 53. Position of the vocal folds during various functional states. The rima glottidis is closed (I), open during quiet breathing (II), and widely dilated (during phonation) (III).

The arrows indicate the direction of muscle pull.

A — laryngoscopic view: 1 — epiglottis, 2 — epiglottic tubercle, 3 — vocal fold, 4 — corniculate tubercle, 5 — cuneiform tubercle, 6 — vestibular fold.

B — diagrams of various positions of the vocal folds, rima glottidis, and arytenoid cartilages: 1 — lamina (right) of the thyroid cartilage, 2 — vocal ligament and vocal muscle, 3 — arytenoid cartilage, 4 — posterior cricoarytenoid muscle, 5 — lateral cricoarytenoid muscle, 6 — transverse arytenoid muscle, 7 — thyroarytenoid muscle

Sex differences in the larynx are not observed at an early age. Subsequently, the larynx grows somewhat faster in boys than in girls. After 6—7 years, the larynx in boys is larger than in girls of the same age. At 10—12 years, the laryngeal prominence becomes noticeable in boys. During puberty, the dimensions of the larynx and the length of the vocal folds are greater in boys than in girls.

The laryngeal cartilages, which are thin in newborns, become thicker with age but retain their flexibility for a long time. In old age, calcium salts are deposited in the laryngeal cartilages, except for the epiglottis; the cartilages ossify, becoming fragile and brittle.

Trachea and Bronchi

The trachea, which is connected superiorly to the larynx by ligaments, extends from the lower margin of the VI cervical vertebra to the upper margin of the V thoracic vertebra. The trachea has a skeleton consisting of 16—20 cartilaginous C-shaped rings that are open posteriorly and connected by anular ligaments. The posterior wall of the trachea, adjacent to the esophagus, is membranous, composed of Connective Tissue and smooth muscle bundles. The tracheal mucosa is lined with ciliated epithelium and contains numerous glands and lymphoid nodules.

At the level of the V thoracic vertebra, the trachea divides into two main bronchi (tracheal bifurcation) — the right and left, which HEAD toward the hilum of each lung. The right main bronchus is shorter and wider than the left, appearing as a continuation of the trachea. The walls of the main bronchi have the same structure as the trachea, with their skeleton formed by cartilaginous C-shaped rings. At the hilum of the lungs, the main bronchi divide into lobar bronchi. There are three lobar bronchi in the right lung and two in the left. The lobar bronchi divide into segmental and other smaller bronchi, which form 22—23 orders of branching in each lung. The branching of the bronchi in the lung is called the bronchial tree. In the walls of medium-sized bronchi, hyaline cartilage is replaced by elastic cartilage plates. In small bronchi, cartilage tissue is completely absent, but Cytology/cytology/32.html">Smooth Muscle tissue is well developed.

Age-related features of the trachea and main bronchi

In a newborn, the length of the trachea is 3.2—4.5 cm, and the width of the lumen in its middle part is about 0.8 cm. The membranous wall of the trachea is relatively wide, and the tracheal cartilages are poorly developed, thin, and soft. In old age (after 60—70 years), the tracheal cartilages become dense and brittle, easily fracturing under compression.

After birth, the trachea grows rapidly during the first 6 months, then its growth slows down and accelerates again during puberty and adolescence (12—22 years). By 3—4 years of age, the width of the tracheal lumen doubles. The trachea of a 10—12-year-old child is twice as long as that of a newborn, and by 20—25 years, its length triples.

The mucous membrane of the tracheal wall in a newborn is thin and delicate; the glands are poorly developed. In a child of 1—2 years, the upper margin of the trachea is located at the level of the IV—V cervical vertebrae, at 5—6 years — anterior to the V—VI vertebrae, and in adolescence — at the level of the VI cervical vertebra. By age 7, the tracheal bifurcation is located anterior to the IV—V thoracic vertebrae, and after age 7, it gradually settles at the level of the V thoracic vertebra, as in an adult. The main bronchi grow particularly rapidly during the first year of life and during puberty.

Lungs

The right and left lungs are located in the thoracic cavity, to the right and left of The Heart and great blood vessels. The lungs are covered by a serous membrane — the Pleura, which forms a closed pleural sac — the pleural cavity — around each lung. In shape, the lung resembles a cone with a flattened medial side, a rounded apex, and a base facing the Diaphragm (Fig. 54).

Each lung has three surfaces: costal, diaphragmatic, and mediastinal. The costal surface is convex and lies adjacent to the inner surface of the thoracic wall. The diaphragmatic surface is concave and lies adjacent to the diaphragm. The mediastinal (medial) surface is flattened. On this flattened side (medial, mediastinal) is the hilum of the lung, through which the main bronchus, pulmonary artery, and nerves enter the lung, while the Pulmonary veins and Lymphatic vessels exit. The bronchi, vessels, and nerves form the root of the lung.

Fig. 54. Lungs. Anterior view:

1 — apex of the lung, 2 — superior lobe of the left lung, 3 — inferior lobe of the left lung, 4 — Base of the lung, 5 — cardiac notch, 6 — interlobar fissures, 7 — inferior lobe of the right lung, 8 — middle lobe of the right lung, 9 — superior lobe of the right lung, 10 — trachea, 11 — larynx

Each lung is divided into lobes by deep fissures. The right lung has three lobes: superior, middle, and inferior; the left lung has two lobes—superior and inferior. Within the lobes, segments are distinguished (10 in each lung), the boundaries of which are not visible on the lung surface. Lung segments consist of lobules. There are approximately 80 lobules in a single segment. Each lobule is entered by a lobular bronchus with a diameter of 1 mm. The lobular bronchus divides into terminal bronchioles, and the terminal ones divide into respiratory bronchioles. The respiratory bronchioles lead to alveolar ducts, which feature tiny outpouchings (vesicles) called alveoli in their walls. A single terminal bronchiole with its branches—respiratory bronchioles, alveolar ducts, and alveoli—is called the alveolar (respiratory) tree, or pulmonary acinus (cluster). The acinus is the Structural and functional unit of the lung, where gas exchange occurs between the blood flowing through the capillaries and the air in the alveoli. In both human lungs, there are about 600—700 million alveoli, with a respiratory surface area of approximately 120 m².

Age-related features of the lungs

In a newborn, the lungs have an irregular conical shape; the superior lobes are relatively small, the middle lobe of the right lung is equal in size to the superior lobe, and the inferior lobe is comparatively large. The average mass of both lungs in a newborn is 57 g (ranging from 39 to 70 g), with a volume of 67 cm³. The density of a non-aerated lung is 1.068 (the lungs of a stillborn infant sink in Water), while the density of the Lung of a breathing child is 0.490. The bronchial tree is largely formed by the time of birth. During the first year of life, its intensive growth is observed (the size of the lobar bronchi doubles, and that of the main bronchi increases 1.5 times). During puberty, the growth of the bronchial tree accelerates again. By the age of 20, the dimensions of all its parts increase 3.5—4 times compared to the bronchial tree of a newborn. The bronchial tree reaches its maximum size in individuals aged 40—45. Age-related involution of the bronchi begins after 50 years of age. In elderly and senile age, the length and lumen diameter of the segmental bronchi decrease slightly, and sometimes moniliform outpouchings of their walls appear.

In a newborn, pulmonary acini contain a small number of tiny pulmonary alveoli. During the second year of a child's life and later, the acinus grows due to the appearance of new alveolar ducts and the formation of new pulmonary alveoli in the walls of already existing alveolar ducts.

The formation of new branches of alveolar ducts is completed by 7—9 years of age, and that of pulmonary alveoli by 12—15 years. By this time, the size of the alveoli has doubled. The Formation of the pulmonary parenchyma is completed by 15—25 years of age. Between the ages of 25 and 40, The structure of the pulmonary acinus remains virtually unchanged. After 40 years, Aging of the lung tissue gradually begins: pulmonary alveoli become larger, and some interalveolar septa disappear. During the postnatal GROWTH AND DEVELOPMENT of the lungs, their volume increases: 4 times during the first year, 8 times by age 8, 10 times by age 12, and 20 times by age 20 compared to the lung volume of a newborn.

Pleura

The pleura is a serous membrane that covers the lungs on all sides, firmly adhering to the pulmonary parenchyma, and forms the walls of the pleural cavities in which the lungs are located. The pleura covering the lungs—the pulmonary, or visceral pleura—reflects at the root of the lung onto the walls of the thoracic cavity, forming a closed pleural sac (right and left) around each lung. The pleura lining the walls of the thoracic cavity is called the parietal pleura. The parietal pleura is subdivided into the costal pleura, adjacent to the Ribs, the diaphragmatic pleura, and the mediastinal pleura. Between the parietal and visceral pleura, There is a narrow space—the pleural cavity—containing a small amount of serous fluid. This fluid moistens the contacting surfaces of the visceral and parietal pleura, facilitating the sliding of the lungs within the pleural cavities.

At the transitions between different PARTS OF THE pleura, there are pleural recesses (sinuses) into which the margins of the lungs enter only during maximal inspiration. The deepest recess is the costodiaphragmatic recess (sinus).

BOUNDARIES OF THE lungs and pleural cavities

In clinical practice, knowledge of the boundaries of the lungs and pleural sacs is of great importance. This information becomes particularly relevant in Pneumonia, pleural diseases (Pleurisy), or when an excessive amount of fluid accumulates in the pleural sacs (such as blood in hemorrhages or injuries). Anteriorly, the apices of the lungs are located 3—4 cm above the I rib, or 2 cm above the clavicle. The inferior boundary is determined with reference to vertical lines. These include the parasternal line, which runs along the border of the Sternum (on both sides), the midclavicular line, drawn vertically through the midpoint of the clavicle, the anterior axillary line (running along the anterior axillary fold), the midaxillary line (extending downward from the deepest point of the axilla), the posterior axillary line (running along the posterior axillary fold), the scapular line (passing through the inferior angle of the scapula), and the paravertebral line, which runs along THE Vertebral Column through the costovertebral joints.

The anterior boundary of the lung extends from its apex through the sternoclavicular joint, then through the middle of the junction between the manubrium and body of the sternum, and further down to the cartilage of the VI rib, where it transitions into the inferior boundary. Along the midclavicular line, the inferior boundary of the lung crosses the VI rib; along the midaxillary line, it crosses the VIII rib; along the scapular line, the X rib; and along the paravertebral line, the XI rib, where the inferior boundary transitions into the posterior boundary, which extends upward along the spine. The inferior boundary of the left lung is located slightly lower than that of the right lung.

The superior and anterior boundaries of the pleura coincide with the corresponding boundaries of the lung. The inferior boundary of the pleura is determined along the same lines as the lung, but is located one rib lower.

Age-related boundaries of the lungs

The boundaries of the lungs change with age. In a newborn, the apex of the lung is at the level of the I rib. Later, it projects above the I rib, and by 20—25 years of age, it is located above the I rib (2 cm above the clavicle). In a newborn, the inferior boundary of both the right and left lungs is one rib higher than in an adult. As the child grows older, this boundary gradually descends. In old age (after 60 years), the inferior boundaries of the lungs are located 1—2 cm lower than in individuals aged 30-40 years.

Mediastinum

The mediastinum is a complex of organs located in the thoracic cavity between the right and left lungs. Anteriorly, the mediastinum is bounded by the posterior surface of the sternum; posteriorly, by the thoracic spine; and inferiorly, by the diaphragm. Superiorly, the mediastinum communicates with the neck region through the superior thoracic aperture. The mediastinum contains the heart and Pericardium, the aorta, the SUPERIOR VENA CAVA, the Thymus, the trachea and main bronchi, the esophagus, the Thoracic duct, mediastinal Lymph Nodes, the vagus and phrenic nerves, as well as other Arteries, veins, and nerves.

REVIEW AND SELF-control questions:

1. Name the walls of the nasal cavity. Indicate where the nasal conchae and nasal meatuses are located and what Functions they perform.

2. List the cartilages and Muscles of the larynx. What functions does each of these muscles perform?

3. What is the root of the lung, and what does it contain?

4. Name the surfaces of the right and left lungs and their boundaries (along the reference lines).

5. What are the bronchial tree and the alveolar tree? How are they structured, and where are they located?

6. Describe the STRUCTURE OF THE pulmonary acinus.

7. What is the pleura, what are its parts, and what functions does it perform?

8. Describe the mediastinum and its boundaries. Which organs are located within it?