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biology, erythrocytes, red blood cells helppp

Explain how erythrocytes are recycled?

Hi,
Erythrocytes have a lifespan of 90 days, then they die. They have a unique very resilient structure as they have to squeeze through capillaries whose lumens can be much smaller than the diameter of the erythrocyte (7 micrometers) - this is especially true of the red cell membrane.

When they die, red cells undergo opsonisation by becoming coated with IgG (immunoglobulin G - a small antibody type) and C3b (complement), which makes it easier for macrophages to engulf them [more often, though, the red cell becomes spherical [called a spherocyte] then its substance is broken down in the spleen]; if this haemolysis [Greek haem = blood; lyso = breakdown, therefore the name given to lysosomes [remember their function?]] is uncontrolled or excessive, haemolytic anaemia results [anaemia]; the contained haemoglobin (Hb) is broken down into porphyrins and eventually into bilirubin (in the liver), and ferrous iron salts [Hb is made of four haem groups with a central atom of iron - the iron remains as ferrous (Fe2+) even when Hb is oxygenated [it is not oxidized to ferric [Fe 3+]]].

You could use the word "recycling" as part of the iron joins the iron stores of the body, including the iron attached to ferritin in the blood [this]. The bilirubin (and biliverdin) are secreted into the bile which enters the gastrointestinal tract at the sphincter of Oddi, hence into the duodenum (first part of small intestine), and is excreted in the faeces (explains the greenish-brown colour of stool).

DON'T WORRY if you can't remember all the above - although some of it can earn extra marks in a possible synoptic Q.

M (specialist biology tutor)

(edited 5 years ago)

Reply 2

laura273

thanks for your helpp but is there any way just to keep things simple and just answer the question, e..g just talk about the recycling of erythrocytes and nothing else.

thankss