Functions and Composition of Blood

Functions of Blood

• Transports oxygen, waste, and hormones
• Prevents infection and blood loss
• Regulates body temperature, pH, and fluid volume

Composition and Characteristics of Whole Blood

• Blood is a connective tissue made of cells suspended in a fluid matrix (plasma)
• Suspended cells are known as formed elements (red blood cells, white blood cells, and platelets)
• Plasma composition: 90% water, 10% dissolved gases, salts, minerals, nutrients, enzymes, hormones, waste, and proteins
• Three types of proteins in plasma: Albumin (regulates osmosis), Globulins (transport substances or fight infection), and Fibrinogen (used in blood clotting)
• Physical characteristics: 5 times more viscous than water, color ranges from bright red to purplish, pH range of 7.35-7.45, and blood volume of 5-6 liters

Erythrocytes (Red Blood Cells)

• Structure: biconcave shape, round sides, no nucleus, and few organelles
• Function: transport oxygen around the body via hemoglobin
• Production: produced in red bone marrow, assist in Hematopoiesis, and lives only 100-120 days

White Blood Cells (WBCs)

• Granulocytes:
  • Neutrophils: engulf and destroy foreign bacteria, most common leukocyte, and more are produced during an infection
  • Basophils: release histamines, which dilate blood vessels
  • Eosinophils: kill parasitic worms and lessen allergic reactions
• Agranulocytes:
  • Lymphocytes: antibody production, direct cell-mediated killing of virus-infected and tumor cells, and regulation of the immune response (2 types: T-cells and B-cells)
  • Monocytes: leave the blood and enter surrounding tissues, becoming macrophages that attack and engulf viruses, parasites, and bacterial infections

Platelets

• Structure: made of tiny fragments of other cells
• Function: clotting the blood when a vessel is broken
• Production: formed and released into the bloodstream by precursor cells called megakaryocytes in the bone marrow

Hemostasis

• Vascular spasms
• Platelet plug formation
• Coagulation
• Clot Retraction and Repair

ABO and Rh Blood Groups

• ABO blood groups: A, B, AB, O
• Antigens and antibodies: antigens trigger antibody production, leading to agglutination
• Rh factor: determined by the presence or absence of an Rh antigen on red blood cells
• Rh+ and Rh- individuals: Rh- people form anti-Rh antibodies when they come in contact with Rh+ blood
• Transfusion reactions: symptoms include fever, chills, urticaria, itching, and potentially serious reactions such as respiratory distress, high fever, hypotension, and red urine (hemoglobinuria)