Question

In human blood the normal number of blood platelets (Thrombocytes) per cubic mm is:
1. 100,000-200,000
2. 200,000-300,000
3. 500,000-700,000
4. 200,000-400,000

Answer 1

Correct Answer - Option 2 : 200,000-300,000

Concept:

• Blood is a special connective tissue consisting of a fluid matrix, plasma, and formed elements
• Plasma is a straw-coloured, viscous fluid constituting nearly 55 per cent of the blood. 90-92 per cent of plasma is water and proteins contribute 6-8 per cent of it.
• Fibrinogen, globulins and albumins are the major proteins
• Erythrocytes, leukocytes, and platelets are collectively called formed elements and they constitute nearly 45 per cent of the blood

Explanation:

• Platelets also called thrombocytes, are cell fragments produced from megakaryocytes (special cells in the bone marrow).
• Blood normally contains 200,000-300,000 platelets mm–3.
• Platelets can release a variety of substances most of which are involved in the coagulation or clotting of blood.
• A reduction in their number can lead to clotting disorders which will lead to excessive loss of blood from the body.

 

• Erythrocytes or red blood cells (RBC) are the most abundant of all the cells in the blood.  A healthy adult man has, on average, 5 million to 5.5 million RBCs mm–3 of blood. 
• Leucocytes are also known as white blood cells (WBC) as they are colourless due to the lack of haemoglobin. They are nucleated and are relatively lesser in number which averages 6000-8000 mm³ of blood.