The vascular system consists of a network of vessels and, along with the heart, provide for circulation of the blood.
Coronary circulation provides blood to the heart. Systemic circulation provides blood to and from the body. Blood travels to and from the lungs and obtains oxygen and removes carbon dioxide from the blood.
Blood vessel layers include the tunica intima (innermost), tunica media (middle), and tunica adventitia (outermost).
All arteries, with the exception of the pulmonary artery, carry oxygenated blood to the body. All veins, with the exception of the pulmonary artery, carry deoxygenated blood back to the heart and lungs. Arterioles are small arteries and venules are small veins. Capillaries provide a link between arterioles and venules and allow for gas exchange.
The three veins most commonly used for phlebotomy are located in the antecubital fossa. They include the median cubital, cephalic, and basilic veins.
Blood is responsible for transporting oxygen and nutrients to the cells and tissues of the body, transporting hormones to their target area, eliminating waste materials (excretion) from the body's cells, maintaining water balance for the cells and tissues of the body, and transporting antibodies and protective substances.
The major components of blood include formed elements (erythrocytes, leukocytes, and platelets) and plasma.
Red blood cells transport oxygen and carbon dioxide. White blood cells destroy foreign invaders and remove cellular debris. Platelets are essential for clotting.
Granular white blood cells include neutrophils for phagocytosis, eosinophils for phagocytosis, and basophils for release of histamine and heparin. Agranulocytes include monocytes that fight chronic infections and lymphocytes that assist the immune system in producing antibodies.
Plasma is the liquid portion of unclotted blood. Serum is the liquid portion of blood collected in a tube without anticoagulant.
Hemostasis or stopping of blood includes four major events: blood vessel spasm, platelet plug formation, blood clotting, and fibrinolysis.
ABO and Rh blood types are determined by the type of antigen found on the red blood cells.
