Erythropoieisis

Question 1

what is erythropoiesis?

Answer 1

-the process by which RBC (erythrocytes) are produced

Question 2

where does erythropoiesis occur in very early foetus, 3rd to 7th month gestation, at birth and from birth to maturity?

Answer 2

Early embryo= yolk sac
3rd to 7th month= spleen
At birth= mostly bone marrow, liver and spleen when needed
birth to maturity= number of active sites in bone marrow decrease but retain ability

Question 3

where does erythropoiesis occur in an adult?

Answer 3

Bone marrow of:
-vertebrae
-ribs
-sternum
-sacrum
-pelvis
-proximal femur

(almost axial skeleton)

Question 4

explain erythropoiesis from a multipotent hematopoietic stem cell to an erythrocyte

Answer 4

1. Begins with a multipotent hematopoietic stem cell (hemocytoblast)
2. Some multipotent hematopoietic stem cells differentiate into common myeloid progenitor cells
3. Myeloid progenitor cells become normoblasts (AKA eryhtroblasts) found only in bone marrow
4. Myeloid progenitor cels then lose their nucleus as they mature into reticulocytes (no nucleus)
5. Reticulocyte lose their remaining organelle and become an erythrocyte (mature RBC)

Question 5

Explain the erythropoitin feedback loop

Answer 5

-interstitial fibroblasts near the peritubular capillaries and the proximal convoluted tubule detect hypoxia in the blood flowing through the kidney
-kidney releases EPO (erythropoietin)
-Eryhtropoietin (EPO) acts on the bone marrow and stimulates cell division of red cell precursors and recruits more cells to red cell production in the marrow
-the result is erythroid hyperplasia

Question 6

explain the breakdown of erythrocytes

Answer 6

BREAKDOWN- eryptosis
-primary site is in the spleen
-have a life span of roughly 120 days
-Macrophages recognize the morphological blue print of an old or unfeasible erythrocyte
-once phagocytosed by the macrophages the haem and globin are seperated
-Globin chains are recycled into amino acids
-Amino acids are later recycled for globin synthesis
-the Haem group is broken down to iron and bilirubin
-Iron is moved into bone marrow to be used for another cycle of erythropoiesis (gets bound to porphyrin ring)
-Bilirubin is then taken to liver and conjugated and then excreted in bile (colour faeces and urine)

Question 7

is breakdown of Hb in the spleen intra or extra vascular?

Answer 7

extravascular