Composition of Blood

Blood is a body fluid that runs throughout the body. It is the medium through which all necessary elements like nutrients and oxygen are transferred to cells and all metabolic wastes are transferred from cells. Blood consists of almost 8% of human body’s weight.

Functions of blood include transportation of necessary elements, protection from the foreign materials like bacteria, fungus etc., and regulation of pH by interacting with acids and bases.

A composition of blood:

Composition of blood

Blood consists of two main components:

  • Plasma
  • Formed elements or corpuscles.


Plasma constitutes almost 55% of blood. Plasma is a pale yellowish, watery substance that surrounds blood cells and carries them around the body.Plasma is a combination or mixture of nutrients, gases, proteins, hormones, salts, and wastes.

Functions of blood plasma

  • Plasma helps to regulate body temperature and maintains blood pressure.
  • Transportation of nutrients is one of the major functions of blood plasma. When a food is digested, it breaks down into amino acids, sugars, lipids and fatty acids. These are transported throughout the body by plasma.
  • Plasma also transports wastes like uric acids, ammonium salts etc., to kidneys, where it filters wastes from plasma and excretes it through urine.
  • Plasma also supplies required proteins for blood clot and immunity.

Formed Elements or Corpuscles

Formed particles or corpuscles consists of

  • Erythrocytes or Red blood cells
  • Leucocytes or White blood cells


These are commonly known as Red blood cells or corpuscles. These play an important role in the transportation of oxygen. A protein called hemoglobin is present inside the red blood cells and that carries oxygen throughout the body.

  • Function: Transportation of oxygen
  • Shape: looks like thick flying saucer
  • Life: Approximately 120 days
  • Birth: Produced in bone marrow
  • Diseases: Anemia is caused due to lack of red blood cells.


These are commonly known as White blood cells or corpuscles. Although these account for only 1% of blood, they are very significant. They are essential for good health and protect the human body from illness and diseases.

White blood cells are soldiers who battle with every foreign invader that enters our system. They flow through the bloodstream and fights with bacteria, the fungus that may affect human bodies. They can be called d defenders of the human body.

White blood cells are classified into

  • Granulocytes
  • Agranulocytes

Where again Granulocytes are classified into

  • Neutrophils
  • Eosinophils
  • Basophils

And Agranulocytes are classified into

  • Lymphocytes
  • Monocytes

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