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 a completely different histological structure and perform dissimilar functions. In the process of embryogenesis, they develop from two germ layers - endoderm and mesoderm. These are human alveoli. They contain the air-bearing tissue of the lungs and depressions in the bones of the upper and lower jaws. Let's take a closer look at these structures.
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, which consists of a huge number of microscopic sac-like formations. The protrusion of the walls of the parenchyma of the respiratory organs, resembling a honeycomb - that's whatalveolus. It is connected with neighboring structures by an interalveolar septum, consisting of two epithelial layers containing flat-shaped cells. Between them are collagen fibers and reticular tissue, intercellular substance and capillaries. All of the above structures are called the interstitium. It should be noted that the network of blood vessels in the lungs is the largest and most extensive in the human body. This is explained by the fact that with their help in the alveoli of the lungs, carbon dioxide is transported from the venous blood to the alveolar cavity and oxygen passes from it into the blood.
Airblood barrier
The portion of air received during inhalation enters the alveoli of the lungs, which are collected, like bunches of grapes, on the thinnest tubes - bronchioles. They are separated from the blood flow by a three-component structure, 0.1-1.5 microns thick, called the air-blood barrier. It includes the membranes and cytoplasm of the 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 must be remembered that the diffusion of gases in the lungs is impossible without such structures as the interalveolar septa, the air-blood barrier, and the 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 inhalation. Macrophages can also phagocytize erythrocytes trapped in the alveolar vesicles.in the event that a person is diagnosed with heart failure, aggravated by symptoms of stagnation of blood in the lungs.
The mechanism of external respiration
The cells of the body are provided with oxygen and released from carbon dioxide thanks to the blood passing through the capillary network of the alveoli. Oxygen and carbon dioxide, released from carbonic acid and its s alts by the enzyme carbonic anhydrase, continuously move through the air-blood barrier in opposite directions. It is found in red blood cells. The scale of diffusion can be judged on the basis of the following figures: about 300 million alveoli that form the lung tissue make up approximately 140 m2 of the gas exchange surface and provide the process of external respiration. The above facts explain what an alveolus is and what role it plays in the metabolism of our body. In fact, it is the main element that ensures the process of breathing.
Histological structure of alveoli
Having examined the anatomy of lung tissue cells, let us now dwell on their species diversity. The alveolus consists of two types of elements, called type I and type II cells. The first are flat in shape, capable of adsorbing particles of dust, smoke and dirt that are in the inhaled air. An important function in them is performed by pinocytic vesicles filled with a protein substrate. They reduce the surface tension of the alveoli and prevent them from collapsing 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 intoalveolar cavity filled with air. Groups of oval type II cells have a foam-like cytoplasm. They are found in the alveolar walls and are capable of active mitosis, which leads to the regeneration and growth of lung tissue elements.
Alveoli in dentistry
The recess in the jaw where the tooth root is located - that's what an alveolus is. Its wall is formed by a compact substance having the form of a plate. It contains osteocytes, as well as s alts of calcium, phosphorus, zinc and fluorine, so it is quite hard and strong. The plate is attached to the bone beams of the jaw and has periodontal bands in the form of collagen fibers. It is also richly supplied with blood and braided with nerve endings. After tooth extraction, a strongly protruding wall of the outer part of the hole and the bone septum remains. The alveoli of the teeth heal within 3-5 months by forming first granulation tissue, which is replaced by osteoid, and then by mature bone tissue of the jaw.