Internal structure of the lungs

Internal structure of the lungs.

Each of the main bronchi , entering through the gates of the lungs into the corresponding lung, branches onto the lobar bronchi.

The right bronchus gives three lobar bronchi, bronchio lobares, of which one is above the artery, and the other two are below the artery. The left bronchus gives two lobar bronchi located under the artery.

Each of the branches brings air to the lungs. The lobar bronchi in turn are divided into segmental bronchi, bronchi segmentales. Each segmental bronchus in both the right and left lungs is dichotomously divided, while the branches of the bronchi decrease in diameter and become small bronchi; There are 9-10 orders of magnitude. Fine branchings with a diameter of about 1 mm are bronchioles, bronchioli.

The whole system of bronchial tubes from the main to bronchioles constitutes the bronchial tree, arbor bronchiatis, which serves to carry out the air flow during breathing. Further branching of bronchioles is the alveolar tree, arbor alveolaris.

As the branching of the bronchi changes the structure of their walls. If in the main bronchi a cartilaginous skeleton occupies on the average 2/3 of a circle, then in the walls of smaller bronchial branches only insignificant quantities, variously shaped cartilaginous plaques, are included. As the cartilage tissue decreases in the wall of the bronchial branches, the mass of connective tissue increases. Bronchioles are devoid of cartilaginous tissue. In the wall of bronchioles there are spiral smooth muscle fibers.

The inner surface of the branches of the bronchial tree is lined with a mucous membrane covered with a multilayer ciliated epithelium, gradually changing into a multi-rowed cubic, and finally in terminal bronchioles into a single-layered cubic ciliated epithelium; Contains a significant amount of mucous bronchial glands, glandulae bronchiales. There are no glands in the bronchioles.

Bronchioles are suitable for secondary pulmonary lobules, lobus pulmonis secundarius, which are separated from each other by connective tissue septa. Inside each lobule, suitable bronchioles are divided into 18-20 bronchioles of the second order, and the latter in turn are divided into respiratory bronchioles, bronchioli respiratorii. Breathing bronchioles bring air to the areas of the lung, called pulmonary acinus. Acini pulmonares (structural unit of the lung), the number of which in one lung reaches 15,000.

Within the acinus, respiratory bronchioles branch onto second-degree bronchioles, and the last respiratory bronchioles give 2-9 alveolar ducts, ductuli alveolares, the wall of which is protruded by vesicles - lung alveoli, alveoli pilmonis. Alveolar courses end with alveolar sacs, sacculi alveoiares. Alveolar courses and alveolar sacs, belonging to a single respiratory alveolus of the last order, constitute the primary lobe. The total number of alveoli in each lung is from 300 to 350 million, and the total area of ​​their respiratory surface is up to 80 square meters.

The wall of the alveolar courses is lined with a single-layered cubic ciliated epithelium and contains elastic fibers. The alveoli of the lung are lined with a single-layer flat (respiratory) epithelium. The alveoli are surrounded by a dense network of capillaries.

Thus, the parenchyma of the lung consists of a system of branching airway tubes (bronchi, their branches, bronchioles, alveoli) and branching blood vessels (arteries and veins), lymph vessels and nerves. All these formations are interconnected by a connective tissue.

Innervation: plexus pulmonales anterior and posterior, formed by nn. Vagi et trunci sympathici.

Blood supply: rr. Bronchiales (from aorta thoracica, a. Subclavia). Venous blood flows out by vv. Bronchiales in v. Azyca and v. Hemiazyca, partly due to anastomoses in the influx of vv. Pulmonales. Lymphatic vessels divert lymph to nodi lymphatici bronchopulmonales (tracheobronchiales superiores et inferiores). Mediastinales anteriores and posteriores (juxtaesophageales pulmonales).

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• Laryngeal cavity
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• External structure of the lungs
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• Border of the lungs
• Pleura