Human Anatomy, Part 1 - K. A. Dyubenko, A. K. Kolomiysev, Yu. B. Chaykovsky 2002

Special Part
Respiratory System, systema respiratorium [respiratory apparatus, apparatus respiratorius] - General Overview
Lungs - Lung Topography

Skeletotopy. The PROJECTION OF THE Lungs onto the Ribs defines their boundaries, which are determined by Percussion or radiography. The apices of the lungs rise 3–4 cm above the clavicle, posteriorly reaching the level of the spinous process of the seventh cervical vertebra (CVII).

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Fig. 294. BOUNDARIES OF THE lungs and Pleura (diagram):

A - anterior view; B - posterior view; C - right view; D - left view

The anterior border of the right lung extends from the apex to the second rib along the parasternal line (linea parasternalis) and further along the same line to the sixth rib, where it transitions into the inferior border. The anterior border of the left lung follows a course identical to that of the right lung down to the third rib; in the fourth intercostal space, it deviates laterally toward the midclavicular line (linea medioclavicularis), from which it descends to the sixth rib and likewise continues into the inferior border.

The inferior border of the right lung crosses the sixth rib along the parasternal line, the seventh along the midclavicular line, the eighth along the midaxillary line (linea axillaris media), the ninth along the posterior axillary line (linea axillaris posterior), the tenth along the scapular line (linea scapularis), and the eleventh along the paravertebral line (linea paravertebralis). The inferior border of the left lung lies 1–1.5 cm lower than that of the right.

The posterior border of both the right and left lungs extends from the apex to the eleventh rib along the paravertebral line.

Syntopy. Medially, the apex of the lung is adjacent to the Subclavian Artery. Covered by the parietal pleura, the costal surface is separated posteriorly from the intercostal Vessels and nerves by the endothoracic fascia. The Base of the lungs rests on the Diaphragm, which separates the right lung from the Liver, and the left lung from the Spleen, left Kidney and suprarenal gland, Stomach, transverse colon, and liver.

Anterior to the hilum, the Medial surface of the right lung lies adjacent to the right atrium; superiorly, to the right brachiocephalic and SUPERIOR VENA CAVA Veins; and posteriorly to the hilum, to the Esophagus. Anterior to the hilum, the medial surface of the left lung is adjacent to the left ventricle; superiorly, to the aortic arch and left brachiocephalic vein; and posteriorly to the hilum, to the Thoracic Aorta.

The Topography of the ROOT elements of the right and left lungs is not entirely identical. On the right, the main bronchus is located superiorly; inferiorly lies the pulmonary artery, anterior and inferior to which are the Pulmonary veins. In the root of the left lung, the pulmonary artery lies superiorly, with the main bronchus situated inferiorly and posteriorly to it, and the pulmonary veins positioned anteriorly and inferiorly to the bronchus.

Anterior to the root of the right lung lie the ascending aorta, superior vena cava, Pericardium, and part of the right atrium; superiorly and posteriorly lies the azygos vein. The root of the left lung is bordered anteriorly by the aortic arch and posteriorly by the esophagus. Phrenic nerves pass anteriorly along both roots, while vagus nerves run posteriorly.

In newborns, the lungs expand During the first breath. By the end of the first year of life, their volume increases 4-fold; by the end of the 8th year, 8-fold; and by age 12, 10-fold. The pulmonary apices in newborns reach only the first rib, and the inferior border lies higher than in adults.

The Blood supply to the lungs has distinct features. Arterial blood reaches the lungs via the bronchial Arteries, while venous blood drains through the corresponding veins. In addition, deoxygenated (venous) blood is delivered to the lungs via the pulmonary arteries. The pulmonary arteries divide into lobar and segmental branches, which further arborize in accordance with The Structure of the bronchial tree. The resulting capillaries form networks around the alveoli, thereby ensuring gas exchange between the alveolar air and the blood. These capillaries coalesce into venules and veins that carry oxygenated (arterial) blood into the pulmonary veins. The pulmonary and bronchial vascular systems are not entirely isolated—anastomoses exist between their terminal branches.

Lymphatic vessels and nodes of the lungs. Superficial and deep lymphatic vessels are distinguished within the lungs. The superficial vessels originate from the pleural lymphatic capillaries. The deep vessels are formed by capillary plexuses surrounding the terminal bronchioles, as well as the interacinar and interlobular spaces. Efferent lymphatic vessels drain into regional Lymph Nodes, which are classified as follows:

1) pulmonary nodes (nodi lymphoidei pulmonales), located within the lung parenchyma, primarily at the sites of bronchial branching;

2) bronchopulmonary nodes (nodi lymphoidei bronchopulmonales), situated in the region of the pulmonary hilum;

3) superior tracheobronchial nodes (nodi lymphoidei tracheobronchiales sup.), lying along the Trachea and the superior surface of the main Bronchi;

4) inferior tracheobronchial or bifurcation nodes (nodi lymphoidei tracheobronchiales inf.), located on the Inferior surface of the tracheal bifurcation and main bronchi;

5) paratracheal nodes (nodi lymphoidei paratracheales), positioned along the trachea.

Innervation of the lungs is provided by Branches of the Vagus nerve, branches of the trunk ganglion, and branches of the phrenic nerve, which form the pulmonary plexus (plexus pulmonalis) near the hilum. The pulmonary plexus is divided into anterior and posterior parts, with its branches forming peribronchial and periarterial plexuses. Sensory innervation of the lungs is mediated by Cells of the inferior ganglion of the vagus nerve and cells of the lower cervical and upper thoracic spinal ganglia. Nerve impulses from the bronchi are conducted primarily via afferent fibers of the vagus nerves, whereas impulses from the visceral pleura travel via afferent spinal fibers.

Sympathetic innervation of the lungs originates from cells in the lateral horns spanning spinal segments Th II–V. Parasympathetic innervation stems from cells of the dorsal motor Nucleus of the vagus nerve. The axons of these cells reach the lungs as part of the branches of the vagus nerve.