Blood Properties and Functions

Blood Properties

• Blood is a red fluid within blood vessels, representing 8% of body weight (5 liters in women, 5.5 liters in men).
• Specific gravity: 1.060 for whole blood, 1.030 for plasma, 1.090 for blood cells.
• Viscosity: 5 times that of water for whole blood, 2 times for plasma.

Blood Components

• Plasma: The fluid portion, comprising 55% of blood volume.
• Cellular Elements: Comprising 45% of blood volume:
  • Red Blood Cells (RBCs): Erythrocytes.
  • White Blood Cells (WBCs): Leukocytes.
  • Platelets: Thrombocytes.

Blood Functions

• Transport:
  • Carries oxygen to tissues and carbon dioxide to the lungs.
  • Transports absorbed nutrients from the gut.
  • Transports waste products for excretion (e.g., urea, uric acid).
  • Transports hormones and regulatory substances.
• Temperature Regulation: Plasma absorbs and distributes heat produced by metabolism.
• Hemostasis: Blood clots to stop bleeding and seal injuries.
• Defense:
  • White blood cells attack invading organisms.
  • Antibodies provide immune defense.
• Nutrition:
  • Provides nutrients for tissues (sugars, amino acids, fatty acids, minerals).
  • Plasma proteins can be broken down for extra amino acids.

Plasma Properties

• Fluid portion of blood, comprising 3.5 liters in a 70 kg man (5% of body weight).
• Yellow color.
• Specific gravity: 1.030.
• pH: 7.4.
• Viscosity: 2 times that of water.
• Osmotic pressure:
  • Crystalloid: 5000 mmHg.
  • Colloid (proteins): 25 mmHg.

Plasma Composition

• Water: 90%, medium for transport and temperature regulation.
• Plasma Proteins: 6-8% of total weight.
• Inorganic Constituents: 1% of total weight (Na+, Cl-, HCO3-, K+, Ca2+, Mg+).
• Other: Nutrients, waste products, dissolved gases, hormones.

What is Serum?

• Fluid remaining after blood clots and the clot is removed.
• Same composition as plasma but lacks fibrinogen and clotting factors II, V, and VIII.

Plasma Proteins:

• Important components that remain in the plasma and perform various functions.
• Do not pass through capillary pores due to their size.
• Exist in a colloidal dispersion.
• Total concentration: 6-8 g/dl.
• Three groups:
  • Albumin: 4-4.5 g/dl.
  • Globulin: 2.5 g/dl (subdivided into α1, α2, β1, β2, and γ globulins).
  • Fibrinogen: 0.3 g/dl.
• Albumin/Globulin (A/G) ratio: 1.2-1.6.

Site of Synthesis of Plasma Proteins

• Most are synthesized by the liver.
• γ-globulins are produced by lymphocytes.