What is alveolus?

Alveolus is a small air bag created at the tip of the smallest lung airways, bronchioles. The primary function of alveoli is the replacement of carbon dioxide for oxygen. Alveoli tissues also perform secondary functions such as the production of hormones, enzymes and pulmonary surfaces. Second, alveolus is a place where inhalation substances such as pathogens, medicines or other chemicals are usually processed. The network of elastic fibers and capillaries, reminiscent of a rounded basket, forms the external structure of each alveolo. These capillaries branch out both from the pulmonary artery and from the pulmonary vein. The blood -respected oxygen is transmitted by the pulmonary artery from the heart to the lungs, while the lung vein carries blood rich in the lungs and back to the heart. Known as capillary bed , blood vessels surrounding alveoli are not only necessary for gas exchange, but also to ensure elastic support of the delicate internal lining of alveoli. This tissue is covered with a damp film of the lung surface -active substance, a liquid substanceábi in alveoli. The pulmonary -active substance helps in diffusion and prevents alveolar collapse during exhalation. The alveolar epithelium is made of two different types of cells, which together with the pulmonary surface -active substance form the respiratory surface of the lungs.

Flat cells and cover most of the surface surfaces of the epithelium in a pattern similar to tile. The fitting cells are connected by close intersections and create a membrane that allows only the smallest molecules to pass between them. These cells facilitate the diffusion of respiratory gases to the capillary bed by allowing the oxygen and carbonate oxide molec, dissolved in the surface -active substance to pass through intracellular spaces.

type II alveolar cells are more numerous than type I cells, yet they occupy a smaller area of ​​alveolar lining. These cell -shaped cells perform a number of important tasks in the alveoli. The main between these tasks je production of pulmonary surface active substance that is necessary for gas exchange. In addition, type II cells synthesize a number of substances important for a healthy lung function. If necessary, type II cells also have the ability to change the form to replace damaged cells of type I.

also inhabiting the epithelium are large round cells known as macrophages . These cells loosely roam alveolar space and receive fine particles such as dust, tar and pathogens. Once they are full, macrophages go into connective tissue outside the alveoli. In smokers or other individuals exposed to a high level of pollutants, accumulated macrophages appear as heavy black residual lung tissue.

Every pulmonary alveolus measures an average of ten thousandths of an inch (about 250 microns), or just over double the thickness of human hair. At birth, an average person has approximately 200,000,000 alveols. In adulthood, this number usually doubles. Despite their small size, it is reflected in the air surface areahu over 1,500 square feet (143 square meters.)