Blood Properties and Components

Blood Properties, Components, and Functions

• Blood is a connective tissue with a liquid matrix (plasma) containing cells and fragments.
• Functions include: transportation (oxygen, carbon dioxide, nutrients, hormones, heat, waste), regulation (homeostasis, pH, temperature), and protection (clotting, white blood cells).
• Physical characteristics: denser and thicker than water, temperature 38°C, pH 7.35-7.45, color varies with oxygen content (bright red/dark red), constitutes 8% of total body mass, average adult volume 5-6 liters.

Blood Components

• Blood is roughly 55% plasma and 45% formed elements (cells and cell fragments).
• Blood Plasma: Mostly water (91.5%) with dissolved solutes (proteins, electrolytes, nutrients, hormones, gases, waste).
  • Key proteins: albumins (54%), globulins (38%), fibrinogen (7%). Liver synthesizes most plasma proteins.
• Formed Elements:
  • Red blood cells (RBCs): >99% of formed elements; transport oxygen.
  • White blood cells (WBCs) & platelets: <1% of formed elements; involved in defense and clotting.
  • Hematocrit: percentage of blood volume occupied by RBCs (38-46% in females, 40-54% in males).

Blood Cell Formation (Hematopoiesis)

• Primary site after birth: red bone marrow.
• Pluripotent stem cells in red bone marrow differentiate into myeloid and lymphoid stem cells.
• Myeloid stem cells form RBCs, platelets, monocytes, neutrophils, eosinophils, basophils.
• Lymphoid stem cells form lymphocytes.
• Key hormones regulating formation: erythropoietin (EPO) for RBCs, thrombopoietin (TPO) for platelets, and various cytokines.

Blood Groups and Blood Types

• Determined by antigens on RBC surfaces (glycoproteins/glycolipids). O-A-B and Rh most important.
• ABO System:
  • Antigens: A and/or B.
  • Antibodies: Anti-A and/or Anti-B (in plasma).
  • Blood types: O, A, B, AB. O has both anti-A and anti-B, A has anti-B, B has anti-A, AB has neither.
• Rh System:
  • Antigen: Rh factor (present = Rh+, absent = Rh-).
  • Antibodies: Anti-Rh (form in response to Rh+ blood).
• Transfusions: Compatible blood types necessary to prevent agglutination (clumping) and hemolysis (rupturing) of RBCs.
  • Universal donor: O-.
  • Universal recipient: AB+.
• Hemolytic Disease of the Newborn (HDN): Rh incompatibility between mother and fetus can lead to destruction of fetal RBCs.

Typing and Cross-Matching

• ABO Typing: Mixing blood with anti-A and anti-B sera to identify presence of A or B antigens.
• Rh Typing: Mixing blood with Rh antiserum to detect presence of Rh antigen.