Blood components

Functions: Blood delivers oxygen, transports nutrients, protects against infection, and helps regulate body temperature and chemical balance.
Contents of Blood: Shown as a test tube, blood is made up of plasma (46–63%) and formed elements (37–54%). Plasma includes water, albumin, globulins, fibrinogen, hormones, nutrients, and wastes. Formed elements consist of erythrocytes (RBCs), leukocytes (WBCs), and platelets. It defines hematocrit as the percentage of RBCs and packed cell volume as the volume of RBCs. Normal counts are: WBCs 4.5–11 × 10⁶/µL, RBCs 3.5–5.5 × 10⁶/µL, and platelets 150–450 × 10³/µL.
Blood Clotting: Describes three pathways—extrinsic (triggered by external trauma), intrinsic (triggered by vessel wall damage), and common pathway (where both meet). Key plasma proteins are albumin (most abundant, transports fatty acids and hormones), globulins (transport iron, lipids, vitamins A, D, K, E), and fibrinogen (produced by the liver, vital for clotting).