Red Cells

Question 1

Where and how are red and white cells produced?

Answer 1

1. Red cells (erythrocytes) and white cells (leukocytes, (granulocytes, monocytes and platelets)) produced in bone marrow
2. Derived from multipoint haemopoietic stem cells (HSCs) 3. Haemopoiesis=prduction of blood cells

Question 2

What are red cells produced under the influence of?

Answer 2

1. erythropoietin

2. synthesised in the kidney 3. reduced oxygen supply to the kidney is a stimulus to erythropoietin synthesis

Question 3

What is the production of white cells under the influence of?

Answer 3

Bone marrow production of granulocytes (neutrophils, eosinophils and basophils) and monocytes is under influcend of multiple cytokines such as the interleukins and granulocyte- and granulocyte-macrophage colony stimulating factors (G-CSF and GM-CSF)

Question 4

What is the production of platelets under the influence of?

Answer 4

thrombopoietin

Question 5

What is the function of HSCs?

Answer 5

• Average person produces more than 500 billion blood cells every day and this needs regulation the number of each blood cell type in circulation
• HSCs give rise to all of the different mature blood cell types and tissues
• HSCs are self renewing cells: when they differentiate, at least some of their daughter cells remain as HSCs, so the pool of stem cells is not depleted
• The other daughter of HSCs (myeloid or lymphoid progenitor cells) can follow any of the other differentiation pathways that lead to the production of one or more specific types of blood cell, but cannot renew themselves

Question 6

Describe the process of erythropoiesis

Answer 6

1. The myeloid stem cell/ precursor can give rise to a pro-erythroblast
2. This in turn gives rise to erythroblasts and then erythrocytes
3. Erythrocytes are biconcave shape, help manoeuvrability through small blood vessels to deliver oxygen
4. Normal erythropoiesis required presence of growth factor erythropoietin
5. Erythropoietin is a glycoprotein that is synthesised mainly in the kidney in response to hypoxia
6. Erythropoietin stimulates the bond marrow to produce more red blood cells

Question 7

How is iron absorbed?

Answer 7

1. Excess iron is potentially toxic to organs such as the heart and liver
2. Excess iron cannot be excreted
3. Only 1-2mg per day is absorbed from the diet
4. Absorption of iron in the gut is carefully regulated according to body sores by hepcidin

Question 8

How do duodenal enterocytes alter iron absoprtion?

Answer 8

1. Hepcidin synthesis is suppressed by erythropoietin
2. In duodenum ferroportin on enterocytes transfers iron from cell into blood stream
3. When storage iron is high or inflmsmotry response in body, hepcidiin synthesis is increased 4. Hepcidin degrades ferroportin
4. This prevents the efflux of iron from the enterocyte, so it is lost when the cell is shed into the gut lumen

Question 9

How is vitamin b12 and folate needed for rbc development?

Answer 9

1. DNA synthesis needs 4 immediate precursors: dATP, dTTP, dCTP, dGTP
2. Vitamin B12 and folate are needed for dTTP synthesis necessary for the synthesis of thymidine
3. Deficiency of Vitamin B12 or folate inhibit DNA synthesis
   Vitamin B12 and folate deficiency affects all rapidly dividing cells:
   -Bone marrow: cells can grow but are unable to divide normally
   -Epithelial surfaces of mouth and gut
   -Gonads

Question 10

How is vitamin B12 absorbed?

Answer 10

1. Stomach: B12 combines with intrinsic factor (IF) made in the gastric partial cells
2. Small intestine: B12-IF binds to receptors in the ileum
3. Vitamin B12 deficiency may result from:
   - Inadequate intake e.g. veganism
   - Inadequate secretion of IF: pernicious anaemia (an autoimmune disorder)
   - Malabsorption

Question 11

What is hypochromia?

Answer 11

1. Hypochromia means that the cells have a larger area of central pallor than normal
2. This results from a lower haemoglobin continent and concentration and a flatter cell
3. Red cells that show hypochromia are described as hypo chromic
4. Hypochromia and microcytosis often go together

Question 12

What is polychromeasia?

Answer 12

• Polychromasia describes an increased blue tinge to the cytoplasm of a red cell
• Indicates that red cell is young
• Polychromatic cells are larger than normal red cells, I.e. polychromasia is one of casues of macrocytosis

Question 13

What are target cells?

Answer 13

-Are red cells with an accumulation of haemoglobin int he centre of the area of central pallor
-Target cells may occur in a number of different conditions:
Obstructive jaundice
Liver disease
Haemoglobinopathies
Hyposplenism

Question 14

What are sickle cells?

Answer 14

• Sickle cells are sickle or crescent shape
• They result from the polymerisation of haemoglobin S which in the deoxygenated form is much less soluble than haemoglobin A
• Haemoglobin S occurs when one or two copies of an abnormal Beta globin gene (Beta subscript S) are inherited
• Caused by mutation in beta globin gene: a charged glutamic acid residue in position 6 is replaced by an uncharged valine molecule

Question 15

What cells become what?

Answer 15

1. Monocytes become macrophages
2. Megakaryocytes become platelets, erythrocytes are RBCs, 3. B cells become plasma cells, granulocytes are basophils, neutrophils, and eosinophils

Question 16

What can stem cells develop into?

Answer 16

• Stem cells can divide into 2 cells with different characteristics:
  1. One is a stem cell that can do the same thing as the original cell
  2. Another cell that can differentiate to a mature cell

Question 17

Where does eryhtropotein come from?

Answer 17

90% of erythropoietin comes from the JUXTATUBULAR INTERSTITIAL CELLS OF THE KIDNEY, but remaining 10% comes from liver

Question 18

What is iron in blood carried by?

Answer 18

Trasnferin