Life Sciences Glossary: Composition of Blood and Whole Blood

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Composition of Blood

Blood is highly complex fluid which is composed of two parts-a liquid, called the plasma and different types of cells which remain suspended in the plasma. The cells are called the blood corpuscles. The plasma constitutes about 55 per cent and the cells about 45 per cent of the total volume of human blood.

The general composition of the whole blood is as follows:

Whole Blood


  • Red Blood corpuscles for erythrocytes (RBC) .
  • White Blood Corpuscles or leucocytes (WBC) ; and
  • Platelets or thrombocytes.


  • Water- 90 to 92 per cent.
  • Solids – 8 to 10 per cent.
    • Inorganic constituents, 0.9 % , sodium, potassium, calcium, magnesium, phosphorus, iron, copper etc.
    • Organic constituents.
  • Proteins: 7.5 % serum albumin, serum globulin, fibrinogen, prothrombin, etc.
  • Non- protein: nitrogenous substances- urea, uric acid, creatine, creatinine, ammonia, amino acids, etc.
  • Fats: Neutral fat, phospholipid, cholesterol, cholestrides, etc.
  • Carbohydrate: glucose, etc.
  • Other substances: Internal secretions, antibodies and various enzymes amylases, proteases, lipases, phosphatases, etc.
  • Colorings matter: they yellow colour of plasma is due to small amounts of bilirubin, carotene and xanthophyll in.

Functions of Blood

The blood performs the following functions in our body.

Transport of Gases

  • Transportation from lungs to various body parts.
  • Transportation from various body parts to lungs.
  • Transport of food substances.
  • Transport of Excretory wastes.
  • Transport of Hormones.
  • Maintenance of water balance of body.
  • Maintenance of pH of body fluids.
  • Maintenance of body temperature by thermo regulation and heat dispersion.
  • To prevent hemorrhage formation of blood clot.
  • Defense of the body from microbes and pathogens by- Phagocytosis by WBC; and Antibodies found in the plasma. Antibodies are specialized proteins which destroy specific antigens.
  • Turgidity: It helps in insemination (by the flood turgidity in male genital organ.
  • Sexual Selection: helps in genetic counselling as Rh factor and M. N. O. P. factors etc. during premarital counselling.

Excretory System

Excretion involves the processes in which substances of no further use or those present in excess quantities are thrown out of the body and thereby maintaining a constant internal environment. Maintaining a constant internal environment is known as homeostasis.

Organs of Excretory Systems

In man, besides kidney excretion is also carried out by:

  • Skin: Sweat (Urea, salts and water) .
  • Lungs: Carbon dioxide and water (alcohol also)
  • Liver: Urea formation.
  • Intestine: Bile pigments, salts of calcium and other heavy metals. Urinary system of man consists of a pair of kidneys, ureters, median urinary bladder and urethra. Kidneys are excretory and homeostatic organs. Kidneys are mesodermal in organ developed from nephrostomies of early embryo.

Urinary System of Man

Kidney is covered by peritoneum on the ventral side. Kidneys are located on the posterior wall of the abdominal cavity on either side of the vertebral column. The right kidneys is slightly lower than the left (reverse in rabbit) because of the large area occupied by the liver. The average adult kidney measures about 11.5 cm (4 inches) long, 5.0to 7.5 cm (2 - 3 inches) wide and 2.5 cm (1 inch) thick. Concavity of kidney is called holus, at this place blood vessels, nerves and lymphatic enter and leave the kidneys.

Internal Structure

  • Capsule: Outer envelope of kidney is made of tough fibrous connective tissue.
  • Cortex: Outer part of kidney, dotted in appearance, it contains Malpighian capsules, PCT and DCT.
  • Medulla: Inner part of kidney, striated and lighter in colour, It contains loop of Henley and collecting tubules.
  • Pyramids: Conical processes formed by the projections of medulla into pelvis (dozen pyramids in each kidney) .
  • Pelvis: A large funnel- shaped space towards the concavity.

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