Question

Which of the following cells has a life-span of 5-9 days?
(a)WBC
(b)Platelets
(c)RBC
(d)None of the above

Answer 1

Hint: Blood performs various functions in the human body. The main function of blood is the transport of oxygen and nutrients to the body tissues.
Other functions of blood include- it helps in regulation of body temperature, fight against infections, helps in clotting etc.

Complete answer:
Human blood consists of Plasma which is a fluid matrix and formed elements. The plasma makes up 55% of human blood. The rest 45% is made up of formed elements. The main function of the blood plasma is clotting of blood.
The formed elements consist of Red blood cells (RBCs), white blood cells (WBCs) and platelets.
WBCs are also called leukocytes. They are white in colour because of the absence of haemoglobin. Nucleus is present in these cells. They have a short life span of around 13-20 days. They are present in lesser numbers than RBCs. When their life span ends, they are destroyed in the lymphatic system.
Platelets are formed from the special cells of the bone marrow called megakaryocytes. Thrombocytes is another name for platelets. They are short lived. They have a lifespan of 5-9 days. When their life span ends, they are removed from the bloodstream.
RBCs are also called erythrocytes. They are biconcave in shape that helps in increasing surface area. Nucleus is absent in RBCs. The haemoglobin is present in RBCs which contain iron. It gives red color to the RBCs. The normal lifespan of RBCs is 120 days. When their life span ends, they are destroyed in the spleen.

Thus the answer of the above question is option (B) platelets which have a very short life span.

Note: Normally, 1 500,00-3,500,00 platelets are present in one microliter of blood. As platelets are involved in the activation and release of various clotting factors, a significant decrease in their number can cause various serious clotting disorders. This results in excessive loss of blood from the body of the affected person.