Ch. 14 Blood Groups

Overview of Blood

  • Blood is the only liquid connective tissue in the body.

  • Main topics covered include:

    • Definition and classification of leukocytes (white blood cells).

    • Structure, function, size, and lifespan of different types of leukocytes.

    • Overview of platelets and erythrocytes (red blood cells).

    • Components of blood and their significance.

    • Blood typing, including antigens and antibodies, and implications for transfusions.

    • Discussion on hemolytic disease of the newborn.

Composition of Blood

  • Blood is a sticky fluid that circulates through blood vessels.

  • Contains living (cells) and nonliving (plasma) components.

Volume of Blood

  • Blood constitutes about 8% of total body volume.

  • Average volume in humans:

    • Males: 5 to 6 liters.

    • Females: 4 to 5 liters.

Components of Blood

  • Blood is composed of two major components:

    • Plasma (liquid portion, nonliving)

    • Constitutes approximately 55% of total blood volume.

    • Made up of 90% water and 10% solid components.

    • Formed Elements (living cells):

    • Erythrocytes (red blood cells)

    • Leukocytes (white blood cells)

    • Platelets

Plasma Breakdown

  • Water: 90% of plasma, contributing to viscosity and circulation.

  • Solids (10%): Includes nutrients, hormones, waste products, and electrolytes:

    • Electrolytes: Charged particles (sodium, potassium, chloride, bicarbonate) that help maintain osmotic balance.

    • Plasma Proteins (mostly made in the liver):

    • Albumin: Maintains blood pH, osmotic pressure.

    • Globulins: Transport proteins (alpha, beta), immune function (gamma globulins).

    • Fibrinogen: Clotting protein that converts to fibrin during coagulation.

  • Nutrient Transport: Includes carbohydrates, amino acids, lipids.

  • Respiratory Gases: Oxygen (picked up in lungs) and carbon dioxide (transported to lungs).

  • Hormones: Hormones travel through plasma to reach target cells.

Formed Elements

  • Erythrocytes (Red Blood Cells)

    • Function: Transport oxygen via hemoglobin.

    • Structure: Disk-shaped, about 7.5 micrometers in size.

    • Lifespan: 100-120 days.

    • Normal count: 4-6 million cells per microliter of blood.

    • Disorders:

    • Anemia: Decreased oxygen-carrying capacity.

    • Polycythemia: Increased red blood cell count leading to blood clotting issues.

    • Sickle Cell Anemia: Abnormal hemoglobin structure reducing oxygen transport efficiency.

  • Leukocytes (White Blood Cells)

    • Total count: 4,800 to 11,000 cells per microliter.

    • Classifications:

    • Granulocytes: Neutrophils, eosinophils, basophils.

    • Agranulocytes: Lymphocytes, monocytes.

    • Relative abundance (% of total leukocytes):

    • Neutrophils: ~60%

    • Lymphocytes: ~30%

    • Monocytes: ~8%

    • Eosinophils: ~2%

    • Basophils: <1%

Detailed Functions of Leukocytes

  1. Neutrophils

    • Most abundant (60%) leukocyte.

    • Count: 3,000 to 7,000 cells/microliter.

    • Functions: Destroy bacteria through phagocytosis and enzyme release.

  2. Eosinophils

    • Approximately 2% of leukocytes.

    • Count: 100 to 400 cells/microliter.

    • Functions: Destroy parasitic worms and involved in allergic reactions.

  3. Basophils

    • <1% of leukocytes.

    • Count: 20 to 50 cells/microliter.

    • Functions: Release histamine and heparin during allergic responses.

  4. Lymphocytes

    • About 30% of leukocytes.

    • Count: 1,500 to 3,000 cells/microliter.

    • Types:

      • T Lymphocytes: Target viruses and tumor cells.

      • B Lymphocytes: Produce antibodies; mature into plasma cells.

  5. Monocytes

    • Largest leukocytes with a U-shaped nucleus.

    • Count: 100 to 700 cells/microliter.

    • Functions: Phagocytosis and activating immune responses.

Platelets

  • Derived from megakaryocytes in the bone marrow.

  • Count: 100,000 to 400,000 per microliter.

  • Functions: Essential for blood clotting by forming a meshwork with fibrin.

  • Lifespan: 5 to 10 days.

Blood Typing and Compatibility

  • Blood typing ensures safe transfusion, matching donor and recipient blood types to avoid reactions.

  • Main blood groups:

    • A, B, AB, O, along with positive (+) and negative (-) Rh factor.

  • Antigens on red blood cells define blood types.

    • Type A: Has A antigens and anti-B antibodies.

    • Type B: Has B antigens and anti-A antibodies.

    • Type AB: Has both A and B antigens, no antibodies.

    • Type O: No A or B antigens, has both anti-A and anti-B antibodies.

  • Rh Factor: D antigen presence.

    • Rh positive (D antigen present): No antibodies against Rh.

    • Rh negative (D antigen absent): Antibodies against Rh present.

Implications of Blood Transfusion

  • Incorrect transfusions can lead to acute hemolytic reactions, causing clumping (agglutination) and subsequent complications.

  • First: Immediate identification and removal of transfused blood are critical.

Hemolytic Disease of the Newborn (HDN)

  • Cause: Rh incompatibility between mother (Rh negative) and baby (Rh positive).

  • If the mother’s antibodies attack the baby’s Rh positive blood cells, it can lead to severe anemia or death.

  • Prevention: Administration of RhoGAM during the first pregnancy to prevent the mother's immune system from producing Rh antibodies.

Conclusion

  • Understanding blood components, types, compatibility, and associated conditions is crucial for medical practice and transfusion safety.