The human lungs are one of the most important organs, without which its existence is impossible. Breathing seems so natural to us, but in fact, during it, complex processes take place in our body that ensure our vital activity. To better understand them, you need to know the structure of the lungs.
In the process of breathing, air passes through two bronchi, which have a different structure. The left one is longer than the right one, but narrower than it, so most often the foreign body enters the respiratory system through the right bronchus. These organs are branched. When entering the lung, the right one branches into 3, and the left one into 2 lobes, which corresponds to the number of lobes of the lungs.
The structure of the lungs is quite complex, because inside them the bronchi branch into many small segmental bronchi. In turn, they pass into the lobular bronchi, which are included in the lobules of the lungs. It is difficult to imagine what the structure of the lungs is without knowing how many lobular bronchi are in them (there are about 1000 of them). Intralobar bronchi have up to 18 branches (terminal bronchioles) that do not havecartilage walls. These terminal bronchioles form the structural component of the lungs, the acinus.
The structure of the lungs is easier to understand when you understand what an acinus is. This structural unit is a collection of alveoli (derivatives of the respiratory bronchioles). Their walls are the material substrate for gas exchange, and the area during a full breath can reach 100 sq.m. The greatest stretching of their respiratory surface occurs during exercise.
The bronchopulmonary segment is the part of the lung lobe that is ventilated by third-order bronchi, branching off from the lobar bronchus. Each of them has a separate broncho-vascular pedicle (artery and bronchus). The segmental structure of the lungs was revealed during the development of the level of medicine and surgery. There are 10 segments in the right lung, and 8 in the left. Due to the fact that the division of the lungs into bronchopulmonary segments was established, it became possible to remove the affected areas of this organ with the maximum preservation of its he althy parts.
In this organ, it is customary to distinguish the following surfaces: mediastinal, diaphragmatic, costal. In the mediastinal there are so-called "gates". Through them, the bronchi, arteries and nerves enter the lungs, and the lymphatic vessels and pulmonary veins exit. All these formations make up the so-called "root of the lung".
The lungs are separated by grooves of varying depth and length. They separate tissues up to the very gates of the lungs. There are 3 lobes of the right lung (lower, upper, middle) and 2 left (lower, upper). The lower beats are the largest.
The structure of the lungs will be incomplete without taking into account the visceral layers of the pleura, which cover each lung and root area and form the "parietal sheet" that lines the walls of the chest cavity. Between them is a slit-like cavity, part of which is called the sinuses (located between the parietal sheets). The largest pleural sinus is the costophrenic sinus (the edge of the lung descends into it when inhaling).
The structure of the lungs explains the processes occurring in them during breathing. In this organ, 2 systems of blood vessels are distinguished: a small circle (consists of veins and arteries involved in gas exchange), a large circle of blood circulation (consists of bronchial arteries and veins that supply arterial blood to ensure metabolism and maintain the vital activity of the lungs themselves). By the nature of their branching, the pulmonary veins are similar to arteries, but differ in their inconstancy. Their source is the capillary network of lobules, interlobular connective tissues, small bronchi and visceral pleura. Interlobular veins are formed from capillary networks, merging with each other. Larger veins are formed from them, passing near the bronchi. Two veins are formed from the lobar and segmental veins in each lung: the lower and the upper (their sizes vary greatly). They enter the left atrium separately.
The number of bronchial arteries is not constant. It ranges from 2 to 6. In 50% of cases, a person has 4 bronchial arteries, going evenly to the left and rightmain bronchi. They are not exclusively bronchial arteries, since they give off branches to various organs of the mediastinum. The beginning of the right arteries is located in the tissue behind the esophagus and in front or under the trachea (between the lymph nodes). The left arteries are located in the tissue below the trachea and under the aortic arch. Inside the lung, the arteries are located in the tissue along the bronchi and, branching out, play a direct role in the blood supply to the rest of its parts and the pleura. In the respiratory bronchioles, they lose their independent significance and pass into the capillary system.
All the blood vessels of the lungs are connected to each other. In addition to the common capillary network, extraorganic and intraorganic anastomoses are distinguished, connecting both circles of blood circulation.
The lymphatic system consists of initial capillary networks, plexus of lymphatic vessels within the organ, efferent vessels, extrapulmonary and intrapulmonary lymph nodes. There are superficial and deep lymphatic vessels.
The source of innervation of the lungs is the nerve plexuses and trunks of the mediastinum, formed by branches of the sympathetic, vagus, spinal and phrenic nerves.
