Body Fluids and Circulation Question 29
29. The life span of human W.B.C. is approximately
(a) less than 10 days.
(b) between 20 to 30 days.
(c) between 2 to 3 months.
(d) more than 4 months.
Show Answer
Answer : a
Hints & Solutions
(a) The white blood cells have a life span of 10 days. Most of the WBCs have a life span which is even less than 1 day. White blood cells or leucocytes are produced in the bone marrow at a rate of about 1000 million per day and help to defend the body against infectious disease and foreign materials as a part of the immune system. In conditions such as leukemia this may rise to as many as 50,000 white blood cells in a single drop of blood (only 1% of blood on average is a white blood cell). As well as in the blood, white cells are also found in large numbers in the lymphatic system, the spleen, and in other body tissues. There are normally between $4 \times 109$ and $1.1 \times 1010$ white blood cells in a litre of healthy adult blood.
