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Composition of Blood


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Blood: An Overview

Everyone aware that human body contains red fluid called blood. Blood is circulating in the body. It is a medium to carry material in the body form one part to the other. For example, dissolved gases, nutrients, hormones and waste products are transported. On average, the quantity of blood in the body is about 5 liters or 7% of the total body weight.1 Life with out blood is impossible, even if some amount is decreased suddenly, it is dangerous. All in all, it is absolutely vital for survival.

Composition of blood

Blood consists of water cells and dissolved solutes.

About 90% of the plasma consists of water and the remaining consists of dissolved substances glucose, amino acids, fatty acids, and proteins like albumin and globulin. It removes waste materials like carbon dioxide, urea and lactic acid. Plasma constitutes 55% by volume of blood and of the remaining 45% is cells etc. The other components of the blood include, serum albumin, blood-clotting factors, electrolytes like sodium and chloride, immunoglobulins, and variety of proteins. Serum is the plasma excluded of proteins.

The cells are classified into three categories as follows.

Red Blood Cells or Erythrocytes

Red blood cell is a biconcave disk shape cell, survives for 120 days in the body. About 4.7– 5.2 million cells are present in 1 cubic millimeter. Its red color is because of iron-containing pigment called hemoglobin.

Red blood cell’s main function is to transport hemoglobin, which carries oxygen from lungs to the tissues and carbon dioxide from the tissues to the lung.1 Thus, RBCs play a major role in transporting oxygen to each and every cell of the body.

White Blood Cells

There are six types of white blood cells (WBCs).

  • Neutrophils
  • Eosinophils
  • Basophils
  • Monocytes
  • Lymphocytes
  • Plasma cells

White blood cells are protective cells of the body. Neutrophils, eosinophils and basophils have granular appearance, therefore, called granulocytes. These are also referred as polymorphonuclear cells due to the presence of multiple nuclei. The granulocytes and monocytes protect the body against the invading organisms.

  • Neutrophils are mature cells and can attack bacteria, virus and other agents circulating in the blood stream. These are more active when a new infection occurs.
  • Eosinophils are useful in fighting against parasitic infection and allergic reactions.
  • Basophils play an important role in the inflammatory and allergic reactions.
  • Monocytes play a role in inflammatory reaction and once they enter into the tissue they transform to macrophages.
  • Lymphocytes are more active in chronic inflammation and their number relatively increases in such conditions.
  • Plasma cells: It is a pale yello fluid component of blood. Its main function is to transport blood cells along with nutrients and waster products etc.

Platelets or thrombocytes:
These are responsible for clotting.2

The platelets play a major role in clot formation and prevention of excess bleeding in case of injuries.


Written by: healthplus24.com team
Date last updated: October 24, 2014