Blood: Physical Properties

Physical Properties of Blood

• Blood volume is approximately 5.5 liters, making up 7-8% of total body weight.
• Red color is due to hemoglobin in red blood cells; arterial blood appears brighter due to oxyhemoglobin.
• Blood is opaque because of cellular components.
• Slightly alkaline with a pH of about 7.4.
• Viscosity is 3-5 times that of water, influenced by cellular components and plasma proteins.
• Specific gravity is 1060 for whole blood, 1090 for cells, and 1030 for plasma.
• Plasma osmotic pressure measures 5500 mmHg.

General Functions of Blood

• Transport Medium:
  • Carries oxygen from lungs to tissues and carbon dioxide in reverse.
  • Transports nutrients from the gastrointestinal tract to tissues.
  • Distributes vitamins and hormones, aiding metabolic regulation.
  • Moves waste products like urea and creatinine to excretory organs.
  • Transfers heat generated from metabolic processes to regulate body temperature.
• Defensive Functions:
  • White blood cells (WBCs) phagocytize microorganisms and produce antibodies.
• Haemostatic Functions:
  • Stopping bleeding via platelets and clotting factors.
• Homeostatic Functions:
  • Maintains acid-base balance.
  • Regulates water balance and substance exchange among blood, interstitial fluid, and external environment.
  • Controls blood glucose and calcium levels.
• Contributes to peripheral resistance, which helps maintain arterial blood pressure.

Composition of Blood

• Consists of cellular elements (45%) and plasma (55%).
• Cellular Elements:
  • Red Blood Cells (RBCs): approximately 5 million/mm³.
  • White Blood Cells (WBCs): ranges from 4000 to 11000/mm³.
  • Platelets: between 150,000 and 300,000/mm³.
• Plasma:
  • Accounts for 5% of body weight and 55% of blood volume.

Plasma Composition

• Water constitutes 90% of plasma; dissolved solutes make up 10% (includes organic and inorganic substances).
• Plasma proteins include albumin (3.5-5 gm%), globulin (2.3-3.5 gm%), fibrinogen (0.3-0.4 gm%), and prothrombin (10 mg%).

Plasma Proteins

• Normal plasma protein levels range from 6-8 gm/dl.
• Types of Plasma Proteins:
  • Albumin: Most abundant; functions in osmotic pressure (28 mmHg).
  • Globulin: Includes types alpha and beta; functions related to immunity.
  • Fibrinogen: Key role in blood clotting.
  • Prothrombin: Involved in coagulation.

A/G Ratio

• Normal range is 1.2 by electrophoresis and 1.6-1.7 by chemical separation.
• A decreased ratio may indicate liver failure or nephritic syndrome.
• An increased ratio can occur in congenital agammaglobulinaemia and AIDS.

Functions of Plasma Proteins

• Carriage and Preservation: Act as carriers for hormones, minerals, and vitamins to prevent rapid losses or diffusion.
• Buffer Function: Plasma proteins contribute 7-15% to the buffer system, helping maintain blood pH.
• Regulation of Capillary Permeability: Influence capillary pore closure; low levels can lead to edema.
• Nutritional Reserve: Can be utilized in gluconeogenesis during starvation.
• CO2 Carriage: Transport carbon dioxide as carbamino compounds.
• Specific Functions:
  • Albumin generates osmotic pressure essential for fluid balance.
  • Gamma globulins function as antibodies for defense.
  • Fibrinogen and prothrombin are crucial for clot formation and viscosity.

This quiz covers the physical properties of blood, including its volume, color, opacity, pH, and viscosity. Understand how these properties contribute to the overall function of blood in the cardiovascular system. Test your knowledge on this vital body fluid!