Types Of Blood Vessels In Human Body
There are three types of blood vessels present in human circulatory system.
• Arteries carry blood from heart and supply to organs. These are thick muscular walled and deep seated. All Arteries carry oxygenated blood except pulmonary arteries which carry deoxygenated blood to lungs for purification. They do not have valves.
• Veins collect blood from the tissue of the organs and Bring it to the heart through two big veins, the superior and Inferior vena cava. Veins carry deoxygenated blood except pulmonary veins. Veins are thin walled and placed more superficially. They contain valves.
Capillaries are extremely thin-walled and narrow. They are closely placed with the cells of the tissue in an organ. Oxygen and food pass into the cells and carbon-dioxide and other wastes pass into the capillaries from the cells.
The following terms should be clearly understood before studying blood group.
• A substance capable of stimulating the formation of an antibody is called antigen.
• It is any substance, a bacteria or virus, that the body regards as foreign and it may be formed in or introduced into the body, it is capable of causing some disease in the body and are present in the red blood cells of the donor.
• It is specialised protein produced by certain white blood cells (lymphocytes) in response to entry into the body of a foreign substance. i.e. antigen in order to render it harmless.