In an adult human, blood accounts for approximately 7-9% of the total body weight. So, for a person weighing 70 kg has 5 to 6 litres of blood circulate around the body. The blood transports nutrients, oxygen and waste molecules from one place to another within the body. Every living cell needs a continuous supply of oxygen and nutrients, and a means to remove waste products. Performing these needs is the primary function of the blood.

Blood Cells and Plasma

Blood is a fluid containing solid elements (such as red blood cells, white blood cells and platelets) and liquid part called plasma in a proportion of 45 % and 55 % of the total blood volume, respectively. The red blood cells contain a protein called haemoglobin which is red in color and contains a lot of iron.

Figure 3.1 Diagram of red blood cells.


The normal RBC count in a healthy adult person accounts for about 4- 6 millions cells per mm3 of blood. White blood cells are cells of the immune system involved in defending the body against infectious diseases. The normal white blood cells (WBCs) in an average healthy adult person is ranging from 5000- 10000 cells per mm3 of blood

Last modified: Tuesday, 28 February 2017, 7:01 PM