Given below is a diagram of a human blood smear. Study the diagram and answer the questions that follow: Given below is a diagram of a human blood smear. Study the diagram and answer the questions that follow:
What is the average lifespan of the component numbered ‘1’?
Topic: Lifespan of a red blood cell
Answer
About 120 DAYS (roughly four months).
WHY SO SHORT: a mature red cell has no nucleus, so it cannot repair itself or divide. It is essentially a bag of haemoglobin, and after about 120 days of squeezing through capillaries it wears out.
Worn-out cells are destroyed in the SPLEEN — which is therefore called the GRAVEYARD OF RBCs. The IRON from the haemoglobin is salvaged and reused, while the rest becomes the BILE PIGMENTS bilirubin and biliverdin. That is why bile is coloured, and why jaundice turns the skin yellow when these pigments accumulate.
Two figures worth carrying together: a red cell lives about 120 days, and about 2.5 million of them are destroyed and replaced every second.