Capillary physiology (role of capillaries in metabolism, regulation of capillary function) PDF

Preview

Summary

Capillary physiology (role of capillaries in metabolism, regulation of capillary function)...

Description

Capillary physiology (role of capillaries in metabolism, regulation of capillary function). Capillaries are the smallest blood vessels in the body. Their average diameter is 79µm, length about 700µm. The total capillary lumen is 700-1000 times greater than that of the aorta. At rest, 25-30% of capillaries function. Increases to 60% during physical work. If all capillaries were opened, the EQS would drop dramatically, and capillary shock would occur. The capillary network varies in different organs:  Extremely dense in heart, skeletal muscle, glands (endo- / exo-);  Less dense in bone, cartilage, adipose tissue (therefore, these tissues temperature lower). Capillary function is determined by their structure:  Thin and semiconductive capillary wall (short diffusion path);  Large surface area 700-1000m2 (functional ~ 30% of all capillaries);  Slow linear blood flow 0.05 cm / s;  Sufficient hydrostatic pressure for filtration in the capillaries of the major circulatory system. The capillaries exchange water, dissolved substances and heat. It occurs by diffusion, filtration, pinocytosis, exocytosis. Hydrostatic pressure (capillary blood pressure): 30-40 mm Hg in capillaries of the large circulatory circulation; Kidney 50-60 mm Hg (due to different inputs and outflows of arterioles); Lung 6-8 mm Hg (Interstitial fluid does not form because this pressure is lower than blood plasma oncotic pressure). Regulation of capillary function - no muscle layer: 1. Doesn't work alone - network only; 2. Entry into the capillary is closed by a smooth muscle fiber - a precapillary sphincter increasing or decreasing the volume of blood entering the capillaries by changing their radius; 3. When all the folds are closed, blood flows from the arterioles to the venules via the metarterioles. Metarteriosol - the beginning of a capillary network, with single smooth muscle fibers in the wall. Metarteriosols gives birth to a network of capillaries;

4. Some organs (lungs, kidneys, liver, limbs, skin) are rich in arterialvenous anastomoses, i.e. direct connection through the arterioles to the venules. Less important for function regulation, but very important for thermoregulation. As the temperature rises, the anastomoses open and the temperature closes when the temperature rises.

5. Tons of precapillary arterioles. The tone (luminosity) of the arterioles that branch directly into the capillaries is very important and depends on the amount of blood flow to the capillaries, which is myogenic autoregulation. At high KS, the wall is stretched, the radiance of the arethriol is narrowed, the folds are closed, and less blood enters the capillary network. As KS decreases, tone decreases (luminosity increases) - more capillaries are opened and more blood is drawn. 6. Metabolic regulation. Arterioles dilate and release precapillary folds:  a decrease in the level of O2 in the blood (called hypoxia);  Increased levels of CO2 in the blood;  Increased H + levels in the blood;  increased levels of histamine;  Fever. 7. Hypoxia stimulates endothelial cells to secrete substances that are vasodilatory operation (another way of regulation). Hypoxia causes:  NO release, which dilates blood vessels;  Prostacyclin release, which also dilates blood vessels;  EDHF (endothelial-derived hyperpolarization factor) - also dilates blood vessels.  The endothelium also secretes endothelin and is vasoconstrictive....