A&P Blood

Blood Types

  • Four Main Blood Types: A, B, AB, O

    • Each type is defined by the presence or absence of antigens on red blood cells.

    • A and B antigens determine the blood type:

      • Type A has A antigens.

      • Type B has B antigens.

      • Type AB has both A and B antigens.

      • Type O has neither A nor B antigens.

  • Rh Factor: Determines if blood type is positive or negative

    • Rh Positive (+): Presence of Rh antigen.

    • Rh Negative (−): Absence of Rh antigen.

    • Not part of the exam, but important for understanding blood compatibility.

  • Erythroblastosis Fetalis:

    • Occurs when an Rh-negative mother has an Rh-positive baby.

    • Mismatch can lead to the mother's body creating anti-Rh antibodies.

    • Can affect future pregnancies and lead to complications.

    • RhoGAM Injection: Administered to first-time mothers to prevent antibody production against Rh antigens.

Blood Plasma

  • Definition: Liquid component of blood, 55% of blood volume.

  • Composition:

    • 90% Water: Solvent for transporting nutrients, waste, and other substances.

    • 10% Solutes: Mainly proteins.

      • Key Plasma Proteins:

        • Fibrinogen: Essential for blood clotting.

        • Globulins: Involved in immune responses, including IgA, IgG, IgM.

        • Albumin: Helps maintain osmotic balance and water retention in blood.

  • Serum: Plasma without blood cells and clotting factors.

Blood Clotting (Coagulation)

  • Purpose: Prevents blood loss from damaged vessels.

    • Essential for maintaining fluid balance within the circulatory system.

    • Involves a series of chemical reactions to form a clot.

  • The Process of Clotting:

    • Initial Mechanism: Platelet plug formation at the site of injury.

    • Key Compounds:

      • Prothrombin: Precursor to thrombin, critical for clot formation.

      • Thrombin: Converts fibrinogen to fibrin, forming a stable clot.

      • Fibrin: Forms a mesh that helps stabilize the clot.

  • Mechanism Steps:

    1. Vessel injury activates clotting factors.

    2. Prothrombin converts to thrombin.

    3. Thrombin converts fibrinogen into fibrin, forming a clot.

  • Factors Influencing Clotting:

    • Preventing Clotting:

      • Intact blood vessels prevent clot formation.

      • Chemicals like heparin act as anticoagulants.

    • Promoting Clotting:

      • Rough spots on vessel walls accelerate clotting.

      • Slower blood flow enhances clot formation.

  • Clinical Enhancements:

    • Applying pressure or using chemical aides can accelerate clot formation in emergencies (e.g., thrombin foam).

Review Questions for Exam Preparation

  • Understand blood type compatibility and transfusion principles.

  • Identify universal donor (Type O−) and universal recipient (Type AB+).

  • Recognize the effects of Rh factor in pregnancy and its clinical implications.