Red blood cells

Question 1

How are RBCs produced

Answer 1

Haematopoiesis:
Multipotent hematopoietic stem cell - myeloid stem cell - proerythroblast - reticulocyte - erythrocyte
They are made in the bone marrow

Question 2

How does the distribution of active bone marrow change with age

Answer 2

• In the foetus, most of haematopoeisis occurs in the yolk, liver and spleen but as the foetus nears birth, more starts to occur in the bone marrow
• As humans age, the bone marrow of the long bones starts to become fattier and less productive
• In adult life, more blood production occurs in the sternum/pelvis/vertebrae/ribs

Question 3

What is the role of erythropoietin (epo) in erythropoiesis

Answer 3

• It increases RBC production by stimulating proliferation, differentiation and maturation of erythroid progenitor cells
• Hypoxia inducible factor in perinephric cells senses O2 levels, then at low O2 levels, mRNA for epo is increased and epo produced
• It is the most important driver of RBC production

Question 4

What is the function of the erythrocyte

Answer 4

• Haemo molecules in RBCs (carries oxygen around body)
• Haemo accepts CO2 and releases O2
• Carbonic anhydrase stored in RBCs
• Carbonic anhydrase catalysing a reversible reaction converting CO2 into HCO3-

Question 5

What is a reticulocyte

Answer 5

It is an immature RBC without a nucleus, having a granular or reticulated appearance. It is the precursor for an erythrocyte

Question 6

What does reticulocyte count measure

Answer 6

The number of reticulocytes in the blood. It is used to estimate the degree of effective erythropoiesis and can help in the diagnosis of different types of anaemia

Question 7

How does a high reticulocyte count occur

Answer 7

Increased EPO response which is seen in anaemia due to blood loss, hemolysis

Question 8

What happens to erythropoiesis at high altitude

Answer 8

The low O2 environment stimulates the body to produce EPO. The decline in EPO concentration then results from elevated erythropoiesis that leads to greater EPO consumption during chronic altitude exposure

Question 9

What happens to erythropoiesis in chronic renal failure

Answer 9

When your kidneys are damaged, they produce less EPO. With less EPO, your body makes fewer RBCs, and less oxygen is delivered to your organs and tissues