The respiratory system consists of pathways that conduct air – the nasal cavity, trachea and bronchi, and the respiratory part itself – the lungs. After passing through the nasal cavity, the air warms up, moisturizes, cleanses and enters first into the nasopharynx, and then into the oral part of the pharynx and, finally, into its laryngeal part. Air can get here if we breathe through our mouths. However, in this case it is not cleaned or warmed up, so we easily catch a cold.
From the laryngeal part of the pharynx, air enters the larynx. The larynx is located in the front of the neck, where the contours of the laryngeal elevation are noticeable. In men, especially thin ones, a ledge protruding forward is clearly visible – Adam’s apple. Women do not have such a protrusion. Vocal cords are located in the larynx. The immediate extension of the larynx is the trachea. From the neck, the trachea passes into the chest cavity and at the level of 4-5 thoracic vertebrae is divided into left and right bronchi. In the region of the roots of the lungs, the bronchi are divided first into lobar, then into segmented bronchi. The latter are further divided into smaller ones, forming a bronchial tree of the right and left bronchi. The lungs are located on either side of the heart. Each lung is covered with a moist shiny shell – pleura. Each lung is furrowed into lobes. The left lung is divided into 2 lobes, the right – into three. Shares consist of segments, segments of segments. Continuing to divide inside the lobules, the bronchi pass into the respiratory bronchioles, on the walls of which many small vesicles, alveoli, are formed. This can be compared with a bunch of grapes hanging on the end of each bronchus. The walls of the alveoli are braided with a dense network of tiny capillaries and are a membrane through which gas is exchanged between the blood flowing through the capillaries and the air entering the alveoli during breathing.
The pulmonary artery, branching in the lung according to the division of the bronchi up to the smallest blood vessels, brings venous blood poor in oxygen from the right ventricle of the heart. As a result of gas exchange, venous blood is enriched with oxygen, turns into arterial and returns through the two pulmonary veins back to the heart in its left atrium. This blood path is called the pulmonary or pulmonary circulation.