3. Plasma

Plasma Component of Blood

Plasma Composition

  • Plasma constitutes the bulk of blood.
  • Composition:
    • 80-90% water.
    • 10-20% solutes.
      • Proteins (majority).
      • Electrolytes.
      • Metabolic nutrients and wastes.
      • Hormones.
      • Gases.

Plasma Proteins

  • Most abundant solutes in plasma.
  • Roles:
    • Osmosis.
    • Transport.
Production
  • Mostly synthesized by the liver.
  • Antibodies (immunoglobulins or Ig) are produced by B cells (a type of white blood cell).
Significance of Origin
  • Liver dysfunction can impair plasma protein production, affecting blood functions (transport, homeostasis, defense).
Contribution to Osmotic Pressure
  • Plasma proteins are charged and large, preventing their escape from capillaries.
  • This keeps fluid in blood vessels by maintaining osmotic pressure.
  • Changes in solute concentration (too few or too many solutes) will shift the amount of fluid in the blood.
Main Plasma Proteins

  • Albumin: Most abundant.

    • Maintains osmotic pressure.
    • Transports hydrophobic substances (free fatty acids, hydrophobic drugs, steroid hormones).

  • Globulins:

    • Antibodies (Immunoglobulins - Ig): Immune defense.
    • Transport Globulins:
      • Transferrin: Transports iron.
      • Thyroglobulin: Transports thyroxine (thyroid hormone).

  • Clotting Factors:

    • 4% of plasma proteins.
    • Essential for hemostasis (blood clotting).
    • Fibrinogen: most abundant clotting factor.

  • Regulatory Proteins:

    • Enzymes: Catalyze reactions.
    • Hormones: e.g., Insulin.

Electrolytes

  • Charged ions in the blood with functional roles.

  • Sodium (Na+):

    • Most abundant cation in extracellular fluid (interstitial fluid and plasma).
    • Role in water balance via osmosis.
    • Essential for neuronal and muscle activation through electrical signaling.

  • Potassium (K+):

    • Most abundant cation in intracellular fluid.
    • Role in neuronal and muscle activation via electrical charge movement.

  • Calcium (Ca2+):

    • Cation involved in neuronal and muscle activation, cell signaling, and muscle contraction.
    • Vital for blood clotting (hemostasis).
    • Important for bone and teeth health.

Role of Electrolytes in Homeostasis

  • Electrolytes contribute to water balance and signal transmission by moving from one compartment to another.
  • Maintaining proper electrolyte balance in blood is crucial for overall bodily function and electrolyte balance in other compartments.
Anions

  • Chloride (Cl-):

    • Most abundant anion in extracellular fluid.

  • Bicarbonate (HCO3-):

    • Important for buffering extracellular fluids, especially in the carbonic acid-bicarbonate buffer system in blood.

  • Phosphate (PO43-):

    • Important for bone and teeth formation (calcium phosphate salts).
    • Role in intracellular buffering.

Other Key Solutes

  • Nutrients: Glucose, amino acids (for energy generation and building blocks).

  • Nitrogenous Wastes: Urea, creatinine (transported to kidneys for elimination; contribute to osmotic pressure).

  • Hormones: Insulin, growth hormone (protein types).

  • Respiratory Gases: Carbon dioxide (waste), oxygen (for ATP generation).

  • The amount of these substances in plasma can indicate the functional status of various bodily systems.