Chapter 6: Overview of Blood

1. Functions of Blood

🩸 Transport:

  • Gases (Oxygen, Carbon dioxide)

  • Nutrients & Waste (Glucose, Urea)

  • Hormones (Regulation of bodily functions)

🛡 Defense:

  • Against disease (White blood cells fight infections)

  • Against bleeding (Platelets aid in clotting)

🌡 Regulation:

  • Temperature (Heat distribution)

  • Water-salt balance (Osmotic balance)

  • Blood pH (Maintaining homeostasis)



2. Composition of Blood

🩸 Formed Elements (45%)

  • Red Blood Cells (Erythrocytes) – Transport gases

  • White Blood Cells (Leukocytes) – Immunity

  • Platelets (Thrombocytes) – Clotting

💧 Plasma (55%)

  • 91% Water

  • 9% Solutes:

    • Gases (O₂, CO₂)

    • Nutrients (Glucose, Amino acids, Fatty acids)

    • Wastes (Lactic acid, Urea)

    • Salts (NaCl)

    • Hormones

    • Plasma proteins:

      • Albumin (Osmotic pressure)

      • Globulins (Transport, Antibodies)

      • Clotting Proteins (Fibrinogen)



3. The Formed Elements

Red Blood Cells (Erythrocytes)

🔹 Structure & Function:

  • Biconcave disks → Increases surface area for gas exchange

  • Contains Hemoglobin (Hb) → Binds oxygen

  • Lacks nucleus & mitochondria → Maximizes oxygen transport

  • Produced in Red Bone Marrow (Erythropoiesis)

    • Stimulated by Erythropoietin (EPO)

  • Recycled by Liver & Spleen:

    • Globin → Recycled into amino acids

    • Iron → Reused for new RBCs

    • Heme → Converted to bilirubin (excreted)

🔹 Gas Transport Mechanisms:

  • Oxygen (O₂):

    • Deoxyhemoglobin + O₂ ↔ Oxyhemoglobin

  • Carbon Dioxide (CO₂):

    • 7% dissolved in plasma

    • 23% binds to globin (Carbaminohemoglobin)

    • 70% converted into bicarbonate (HCO₃⁻)

White Blood Cells (Leukocytes)

🦠 Function: Immunity & defense

🔹 Types of WBCs:
 1⃣ Granular Leukocytes:

  • Neutrophils (50-70%) – Phagocytosis of pathogens & debris

  • Eosinophils (Rare) – Fight parasites, manage allergies

  • Basophils (Very rare) – Contain histamine (Inflammation & allergies)

2⃣ Agranular Leukocytes:

  • Lymphocytes (25-35%) – Immunity (B & T cells)

  • Monocytes (3-9%) – Phagocytosis, clean-up function

🔹 Key Features:

  • Have a nucleus

  • Undergo diapedesis (Can move through blood vessel walls)

Platelets (Thrombocytes)

🔹 Function: Blood clotting (Coagulation)
🔹 Fragments of Megakaryocytes
 🔹 Blood Clotting Process:

  1. Blood vessel is punctured

  2. Platelets form a plug

  3. Prothrombin activator triggers a cascade

  4. Fibrin threads form a clot



4. Blood Typing & Compatibility

🔬 Blood Types & Antigens:

  • RBCs have antigens (cell markers)

  • Two main antigen groups:

    1. ABO Blood Group

      • A, B, AB, O

      • A & B are dominant, O is recessive

    2. Rh Blood Group

      • Rh+ is dominant, Rh- is recessive

💉 Blood Compatibility & Transfusions:

  • Universal Donor: O-

  • Universal Recipient: AB+

  • Incompatible blood types → Agglutination (clumping)

👶 Hemolytic Disease of the Fetus (HDFN):

  • Occurs when Rh- mother carries Rh+ fetus

  • Mother’s immune system attacks baby’s RBCs



Memory Devices & Study Tips

🔹 Mnemonics:

  • Blood Functions: "T-D-R" (Transport, Defense, Regulation)

  • Plasma Solutes: "Good Nurses Wear Stylish Hats & Pearls"

    • Gases, Nutrients, Wastes, Salts, Hormones, Proteins

  • WBC Order (Most to Least Abundant): "Never Let Monkeys Eat Bananas"

Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils