The blood circulation in the lungs and the brain

The blood vessels of the lung tissue and bronchus blood comes from the systemic circulation and the pulmonary alveoli into the vessels – from the right ventricle, i. e. in a small circle of blood circulation. The surface of the capillaries of the pulmonary circulation of about 70 cm2. All blood passes through the lungs for 6 seconds. The vessels have a small circle of relatively small length and underdeveloped muscle system. Arteriolar lumen light is 4-5 times greater than arteriolar lumen of the large circle. Therefore, the resistance in the pulmonary blood is much smaller and the pressure of the blood in the pulmonary artery of man is 30 mm. Hg. Art. In a small circle runs as much blood, how much and through a large and minute volume of the right ventricle is typically minute volume of the left ventricle.

The pulmonary vessels due to their great ability to stretch the pressure varies little, and the number of blood contained in them can vary significantly. Inhalation pulmonary capillaries are stretched and blood flow to the lungs is increased, and when you exhale, on the contrary, fallen down the capillaries and increases the blood flow from the lungs. Therefore, the breath in the lungs is about 10%, and when you exhale about 5% of all blood. The number of blood vessels in the lungs may be up to 25% of the entire mass of blood.

Increased pressure in the arterial vessels of the lungs causing depressor reflex that prevents stagnation of blood in the lungs, causing it to drain in a large circle. In this work the right ventricle decreases. Conversely, when the pressure in the large circle simultaneously with the fall of the heart and the great circle vasodilatation reflex increases pulmonary vascular hyperemia.
Blood flow to the brain is extremely important. When the blood pressure in arteries falls to 60-70 mm Hg. Art., the result of insufficient blood supply and accumulation of hydrogen ions and metabolites excited vasoconstrictor center of the medulla oblongata, which causes a rise in the overall blood pressure. At rest, the magnitude of blood flow through the brain of the person is 50-65 cm3 per 100 grams per minute. When mental work it does not change.


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The blood circulation in the lungs and the brain