Transport Systems


The blood transports various substances in the body. A healthy adult body contains 5 to 6 litres of blood. Blood consists of two parts: plasma and cells suspended in it.


Plasma consists of water and dissolved or suspended substances. These substances include:

  • Nutrients
  • Oxygen
  • Chemical substances such as hormones
  • Waste materials such as urea

Blood cells

There are three types of blood cells. These are:

  • Erythrocytes: Erythrocytes or Red Blood Cells (RBCs) transport oxygen between the lungs and tissues of the body. RBCs also transport a small amount of carbon dioxide from tissues to the lungs.
  • Leukocytes: Leukocytes or White Blood Cells (WBCs) fight microbes and other foreign bodies that enter the body. There are many types of leukocytes which perform different protective functions.
  • Thrombocytes: Thrombocytes or Platelets are small cell fragments which play an important role in the clotting of blood.They stop bleeding by clumping and clotting blood vessel injuries.

Next: Circulatory sysetm