Components of Blood

Components of Blood

  • Blood is essential for transporting nutrients, oxygen, and waste products in the body.

Structure of Blood

  • Adult Blood Volume: Approximately 5 liters

  • Composition:

    • Plasma: Liquid portion of blood, containing various proteins and solutes.

    • Serum: Fluid obtained after blood has clotted and cells have been removed.

    • Cellular components:

      • Red Blood Cells (Erythrocytes)

      • White Blood Cells (Leukocytes)

      • Platelets (Thrombocytes)

Plasma Composition

  • Water: 92% by weight, crucial for maintaining blood volume and transporting substances.

  • Proteins: 7% by weight, comprising:

    • Albumins (58%): Maintain osmotic pressure and transport substances.

    • Globulins (37%): Involved in immune responses.

    • Fibrinogen (4%): Essential for blood clotting.

    • Regulatory Proteins (1%): Include hormones and enzymes.

  • Other Solutes: 1% by weight

    • Electrolytes, Nutrients, Respiratory Gases, Waste Products

Cell Counts in Blood

  • Platelets: 12-300 thousand per cubic mm

  • Leukocytes (White Blood Cells): 5-10 thousand per cubic mm

    • Types:

      • Neutrophils: 60-70%

      • Lymphocytes: 20-25%

      • Monocytes: 3-8%

      • Eosinophils: 2-4%

      • Basophils: 0.5-1%

  • Erythrocytes: 4.2-6.2 million per cubic mm

Characteristics of Plasma

  • Appearance: Straw-colored liquid

  • Contains:

    • Salts, Glucose, Amino Acids, Vitamins, Urea, Proteins, Fats

Erythrocytes – Red Blood Cells

  • Shape: Biconcave discs, allowing flexibility and surface area for gas exchange.

  • Primary Function: Transport oxygen throughout the body.

  • Hemoglobin Composition:

    • Heme: Contains iron, crucial for oxygen binding.

    • Globin: Protein component of hemoglobin.

  • Normal Count per Microliter: 4.2 – 6.2 million, making up 45% of blood volume.

Leukocytes – White Blood Cells

  • Larger than erythrocytes.

  • Primary Function: Fight infections and respond to pathogens.

  • Average Count: 5-10 thousand per microliter.

  • Types of Leukocytes:

    • Neutrophils

    • Eosinophils

    • Basophils

    • Lymphocytes

    • Monocytes

Types of Leukocytes and Their Functions

Neutrophils

  • Comprise 60% of WBCs.

  • Function: Main defense against bacteria via phagocytosis.

  • Nuclear Structure: Multi-lobed (PMNs, polys, or segs).

Eosinophils

  • Comprise 2% of WBCs.

  • Function: Combat multicellular parasites and active in allergic reactions.

Basophils

  • Comprise 1% of WBCs.

  • Function: Active during allergic responses.

    • Release histamine (increases permeability of blood vessels) and heparin (prevents clotting).

Monocytes

  • Comprise 4% of WBCs.

  • Function: Kill bacteria and clean up dead cells.

    • Migrate to tissues becoming macrophages living for months to years.

Lymphocytes

  • Comprise 4% of WBCs.

  • Function: Direct the body’s immune response; have memory to recognize pathogens.

  • Types:

    • T-cells: 75% of lymphocyte population.

    • B-cells: Produce antibodies.

Thrombocytes - Platelets

  • Function: Essential for blood clotting.

  • Characteristics: Smallest solid component of blood; fragments of megakaryocytes.

  • Lifespan: Average 10 days.

  • Average Count: 12 – 300 thousand per microliter.