Blood Functions and Characteristics

Functions of Blood

• Transport: Nutrients, wastes, gases (oxygen & carbon dioxide)

• Regulation: Body temperature, pH, and osmotic pressure

• Protection: Clot formation, immune response against pathogens

Characteristics of Blood

• Composition: Cells in a liquid extracellular matrix (plasma)

• Density: 1.06 g/mL

• Temperature: 37°C

• pH: 7.35–7.45

• Body Weight Percentage: 8%

• Volume: 5-6L (males), 4-5L (females)

Components of Blood

Plasma

• Liquid portion making up 55% of blood volume

• Composition: 91.5% water, 7% proteins (albumins, globulins, fibrinogens), 1.5% solutes (salts, nutrients, wastes, hormones)

Formed Elements

• Comprise 45% of blood volume

• Types:

  • Red Blood Cells (RBCs): Oxygen transport, biconcave shape, no nucleus

  • White Blood Cells (WBCs): Immune protection, 5 types (neutrophils, lymphocytes, monocytes, eosinophils, basophils)

  • Platelets: Blood clotting, fragments of megakaryocytes

Hemopoiesis

• Blood cell production, starts in yolk sac, proceeds to liver & bone marrow

• Pluripotent stem cells differentiate into various blood cells

Erythropoiesis

• RBC formation triggered by hypoxia

• Kidneys release erythropoietin to stimulate RBC production

Leukocytosis

• Increase in WBCs due to infection or stress

Hemostasis

• Processes to stop bleeding:

  • Vascular spasm

  • Platelet plug formation

  • Clotting (coagulation)

• Fibrinolysis: Process to dissolve clots after healing

Blood Groups

• Antigens: Substances provoking immune responses

• Antibodies: Proteins binding to specific antigens

• ABO Groups: A, B, AB, O types based on antigens present

• Rh Factor: Rh+ (with antigen) vs. Rh- (without antigen)

Blood Chemistry Tests

• Plasma: Liquid portion requiring anticoagulants to remain liquid

• Serum: Plasma without fibrinogen, obtained after clotting