Explain how erythrocytes are recycled?

Question

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Answer 1

Erythrocytes are recycled after about 120 days, the location this primarily occurs is in the liver(previously it was thought that it occurred primarily in the spleen). The Cells Responsible for the recycling are kupffer cells(phagocyte WBCs located in the liver)

Erythrocytes are non nucleated and don't contain mitochondria, Most of the RBC is Hemoglobin (Heme= Iron+Porphyrin, Globin=Protein). The Body always needs a set amount of iron to replenish the hemoglobin that is lost/destroyed.

When The kupffer cells Engulf the RBC it breaks down the Hemoglobin into the parts that produced it , Iron and globin. The Globin can be further broken down to liberate the amino acids that were used to produce it.

The Heme is much more complex, it is broken down into Iron and Bilirubin. The iron is taken up by the Macrophages and delivered to the bone marrow to produce more RBCs.(iron cannot exist unbound to anything in blood because it acts as a free radical and produces damage to cells). If the iron is not needed by the Bone marrow it can stay in liver bound to Ferritin. If the bone marrow needs the iron it is transported bound to Tranferrin, Once in the bone marrow it undergoes a complex series of reactions to be bound to porphorin and produce Heme. Ferritin and tranferrin help us determine the iron status of a person.

The bilirubin(called indirect bilirubin or unconjugated bilirubin if found in the blood before it reaches the liver) bound to albumin travels to the liver. Once at the liver it is conjugated by UDP-Glucuronosyl Transferase (enzyme) to make conjugated bilirubin which is then sent to the gall bladder. When we eat the gall bladder gets a stimulus from the intestine to contract and releases the bile(contains the bilirubin).

The Conjugated bilirubin now has 2 options, to be Reabsorbed or excreted

The bacteria in the G.I convert Conjugated bilirubin into Urobilinogen where 80 Percent of this will be excreted in feces (where now it is known as Stercobilin, this is what gives feces its brown color). Of the other 20 percent, a very small amount will go to the kidneys where it will be excreted out in urine as urobilin (this gives urine the yellow color). The greater amount of the 20 percent will be reabsorbed and sent back to the liver.