Composition of Blood and their Important Functions in Detail

Blood is the liquid connective tissue in the body. This blood is essential for life activities and has many components. Broadly it can be classified as a cellular fraction which makes 45 % and plasma which comprises 55%.

Composition of Blood

1.Blood cells

a) Red blood cells

b) White blood cells

c) Platelets or thrombocytes


Blood cells:

This portion forms 40% of the total blood. It has formed elements called cells. These cells are all formed in the bone marrow and released into the bloodstream.

Red blood cells

These cells are called as red blood corpuscles or erythrocytes. The blood is red in color due to the presence of these cells in large concentrations. They have hemoglobin in their matrix and helps in carrying oxygen from the lungs to the tissues.

Composition of Blood - Blood cells

White blood cells

These cells are white in color and are three types like the Neutrophils, Acidophils, Basophils, Monocytes, and lymphocytes.

These white blood cells help to combat infections and help prevent infectious diseases.


These cells are also called platelets. These cells are involved in hemostasis.


This is the fluid portion which makes up 55% of the composition of Blood. It has up to 90% of water and 10% of soluble and suspended materials. The solid material includes

  1. Proteins like albumin and globulin.
  2. Nutrients
  3. Gases (Oxygen, carbon dioxide)
  4. Waste material
  5. Lipids
  6. Electrolytes like Na+, Ca+
  7. Hormones
  8. Enzymes

Proteins: Mainly proteins like serum albumin and globulin are present. Albumin contributes to the osmotic pressure of the blood. It helps the blood stay within the blood vessels and prevents leaking.

Globulin has an immune function.


Blood carries nutrients like the glucose, amino acids, fatty acids from the digestive system to other tissues. Glucose is meant for energy generation in the form of ATP. Amino acids are used as building blocks for protein synthesis.

Gases (Oxygen, carbon dioxide)

Oxygen and carbon dioxide gases are present in the plasma. Oxygen is supplied from the lungs to the tissue. CO2 is carried from tissues to the lungs for expiration.

Waste material

Waste material is carried from the tissues to the kidney for excretion. These include urea, uric acid, ammonia, etc.


Lipids like the HDL, LDL, VLDL are present in the blood.


These help in proper function of the nervous system and also help in the movement of substances into the cell.


Hormones are the substances released from the endocrine glands. These are carried away to the tissue.

Enzymes SGPT, SGOT, etc are present in the plasma.

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