Wednesday, September 11, 2019

Functions of Blood | Composition of Blood | Properties of Blood

What is Blood?
Blood is a specialized fluid connective tissue. It is composed of cells which are called formed elements and the liquid portion known as plasma. 
Blood cells
Fig: Blood cells
Characteristics of Blood:
There are some key characteristics of blood which are listed in the below:
  • Color: Red (Due to hemoglobin).
  • Volume: The average volume of blood in a normal adult is 5L.
  • pH: 7.4
  • Specific gravity: of total blood is 1.052 to 1.061
  • Viscosity: Blood is generally 5 times more viscous than water. 
Main Functions of Blood:
Blood performs several functions as follows-

1. Transportation or Distribution:
It includes-
  • Transport of oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs.
  • Transport of nutrients absorbed by the digestive tract to all the body cells.
  • Transport of metabolic waste products to the kidneys, lung, skin, and intestines for removal.
  • Transport of hormones from the endocrine glands to their target organs and tissues.
  • Transport of enzymes.
2. Regulation:
It includes-
  • Maintenance of normal pH (acid-base balance) in the body tissues.
  • Maintenance of appropriate body temperature.
  • Maintenance of body fluid or water content of the body.
  • Regulation of blood pressure.
  • Regulation of colloidal osmotic pressure.

3. Protection:

It includes-
  • Prevention of infection by the WBC and circulating antibodies.
  • Prevention of blood loss by initiating coagulation when blood is damaged.
Components of Blood or Plasma:
Compositions of blood or plasma have presented in the below:

Whole blood consists of formed elements (45%) and plasma (55%).


1. Formed Elements (45%):

It includes-
  • Red blood cells (RBC) or Erythrocytes,
  • White blood cells (WBC) or leukocytes,
  • Platelets.
White Blood Cells (WBC) or Leukocytes:
It includes-
  • Neutrophils (60-70%),
  • Eosinophil (2-4%),
  • Basophils (0-15%),
  • Lymphocytes (20-25%),
  • Monocytes (3-8%).
2. Plasma (55%):
It includes-
  • Solids (10%): Organic electrolytes and inorganic electrolytes.
  • Water (90%),
  • Gases: Oxygen, carbon dioxide and nitrogen.
Organic Electrolytes:
It includes-
  • Proteins: Albumin, globulin and fibrinogen.
  • Nutrients: Glucose, amino acids, fatty acids, glycerol, triglycerides, cholesterol, and vitamins.
  • Non-protein Nitrogenous Substances: Urea, uric acid, creatine, creatinine, ammonium, and xanthine.
  • Others: Metabolic enzymes, antibodies, complement, and hormones.
Inorganic Electrolytes:
It includes-
  • Cations: Na+, k+, ca++, Mg++,
  • Anions: Cl-.
More questions related to this article:
  1. What do you mean by blood?
  2. Define blood.
  3. What are the characteristics of blood?
  4. Mention the key properties of blood.
  5. What are the functions of blood?
  6. Discuss all the functions of blood.
  7. What are the compositions of blood?
  8. Write down the compositions of blood.
  9. Write a short note on blood.