What is the alveolus. Lung alveoli

Anatomical formations, which will be discussed in this paper, are part of two systems of the human body: respiratory and digestive. Outwardly resembling holes or cells, they have completely different histological structure and perform different functions. In the process of embryogenesis, two embryonic sheets develop - the endoderm and the mesoderm. These are human alveoli. They contain airy lung tissue and indentations in the bones of the upper and lower jaw. We will get acquainted with these structures in more detail.

External structure of structural units of lung tissue

Human lungs are paired organs that occupy almost the entire cavity of the chest and provide oxygen to the cells of the body and remove excess carbon dioxide and water. Constant gas exchange is possible due to the unique structure of the lung tissue, consisting of a huge number of microscopic saccular formations. The protrusion of the walls of the parenchyma of the respiratory organs, resembling bees' honeycombs - that is what is the alveolus. With adjacent structures, it is connected by an interalveolar septum consisting of two epithelial layers containing flat-shaped cells. Between them are fibers of collagen and reticular tissue, intercellular substance and capillaries. All the above listed structures are called interstitium. It should be noted that the network of blood vessels in the lungs is the largest and branched in the human body. This is explained by the fact that with their help in the alveoli of the lungs, transport of carbon dioxide from the venous blood into the alveolar cavity and the passage of oxygen from it into the blood are provided.

Aerogematic barrier

The portion of air received during the inhalation enters the alveoli of the lungs, which are collected, like grape clusters, on the thinnest tubules - bronchioles. From the bloodstream they are separated by a three-component structure, 0.1-1.5 μm thick, called the air-blood barrier. It includes membranes and cytoplasm of alveolar elements, parts of the endothelium and its liquid contents. For a better understanding of what an alveolus is and what its functions are, it is necessary to remember that diffusion of gases in the lungs is impossible without such structures as interalveolar septa, air-blood barrier, and interstitium, which contains fibroblasts, macrophages and leukocytes. An important function is performed by alveolar macrophages located inside the alveolar septa and near the capillaries. Here they break down harmful substances and particles that enter the lungs during inspiration. Macrophages can also phagocitate erythrocytes trapped in alveolar vesicles in the event that a person is diagnosed with heart failure, which is burdened by symptoms of blood stagnation in the lungs.

The mechanism of external respiration

The cells of the body are provided with oxygen and are released from carbon dioxide thanks to blood passing through the capillary network of the alveoli. Oxygen and carbon dioxide, which is liberated from carbonate acid and its salts by the enzyme carbonic anhydrase, continuously move through the air-blood barrier in opposite directions. It is in the red blood cells. The scale of diffusion can be judged from the following figures: about 300 million alveoli forming the pulmonary tissue make up about 140 m ^{2 of} the gas exchange surface and provide the process of external respiration. The above facts explain what is the alveolus and what role it plays in the metabolism of our body. In fact, it is the main element that provides the process of breathing.

Histological structure of the alveoli

Having considered the anatomy of the cells of lung tissue, let us now dwell on their species diversity. The alveoli consists of two types of elements called cells of the I and II type. The first - a flat shape, capable of adsorbing the particles of dust, smoke and dirt that are in the inspired air. An important function in them is performed by pinocytosis vesicles filled with a protein substrate. They reduce the surface tension of the alveoli and prevent their decay during exhalation. Another element of type I cells is the closing structures that serve as a buffer and do not allow the intercellular fluid to penetrate into the cavity of the alveoli filled with air. Groups of type II oval cells have a cytoplasm resembling a foam. They are found in the alveolar walls, capable of active mitosis, and this causes the regeneration and growth of the elements of the lung tissue.

Alveola in dentistry

Deepening in the jaw, in which the dental root is located - that's what the alveolus is. Its wall is formed by a compact substance, which looks like a plate. It contains osteocytes, as well as salts of calcium, phosphorus, zinc and fluorine, so it is sufficiently firm and strong. The plate is attached to the bony beams of the jaw and has periodontal strands in the form of collagen fibers. Also, it is abundantly supplied with blood and braided with nerve endings. After the extraction of the tooth, a strongly protruding wall of the outer part of the socket and bone septum remains. Heals the alveoli of the teeth for 3-5 months by first forming a granulation tissue, followed by the osteoid and then the mature bone tissue of the jaw.