RBCs

Question 1

what are the 3 properties of red blood cells

Answer 1

1. unique shape and deformability (membrane)
   
   • allows gas exchange and movement through capillaries
2. energy source (enzyme pathway)
   - needs energy to keep Hb in reduced state and maintain osmotic equilibrium
   - glycolysis
   - HMP shunt
3. Haemoglobin
   - gas exchange

Question 2

what is the clinical implications of the haemoglobin properties of RBCs

Answer 2

• deficiency of iron = reduced production of haem resulting in low Hb (anaemia)
• Impaired production of globin chains results in low Hb (anaemia) = thalassemia

Question 3

what is the clinical implications of the membrane properties of RBCs

Answer 3

abnormalities of the membrane can result in shortened lifespan of the red cell e.g. hereditary spherocytosis

Question 4

what is the clinical implications of the enzyme pathway properties of RBCs

Answer 4

inherited defects in enzyme pathways leads to haemolysis (shortened red cell survival) e.g. G6DP enzyme deficiency

Question 5

describe thalassaemia

Answer 5

Inherited mutation in beta or alpha chain so therefore globin affected and less haemoglobin present

Question 6

erythroid development

Answer 6

1. haemopoietic stem cell
2. common myeloid progenitor
3. early erythroid progenitor e.g. BFU-E and CFU-Es
4. reticulocyte
   
   • have RNA therefore measureable
5. erythrocyte (mature RBC)

Question 7

erythropoietin

Answer 7

regulates erythropoiesis

• is a glycoprotein, produced in the kidneys
• produced in response to low O2
• feedback loop

Question 8

red cell destruction

Answer 8

• RBCs last 120 days
• cells less deformable, removed in spleen
• breakdown of RBC with release of HB
  
  • globin chain reused
  • haem

Question 9

what is haem broken down to

Answer 9

iron -> transferrin -> bone marrow

protoporphyrin -> bilirubin -> liver -> bile (jaundice)

Question 10

process of erythropoiesis and changes

Answer 10

takes 7-10 days

• Hb added
• complete loss of nucleus
• reticulocyte is extruded from marrow
• RNA lost => mature RBC

Question 11

effects of EPO

Answer 11

increased O2 delivery

• increased BFU-E and CFU-E
• increased Hb synthesis
• decreased RBC maturation time
• increased reticulocyte release

Question 12

factors impairing normal reticulocyte response

Answer 12

• deficiency of iron, B12, folate
• lack of EPO (renal disease)
• ineffective erythropoiesis
  e. g. abnormal marrow function, thalassemia
• chronic inflammation, malignancy

Question 13

erythropoiesis during hypoxia

Answer 13

• is promoted by HIF-1 alpha and beta
• up regulates transferrin receptor = more iron into the red cell
• angiogenesis promoted
• glycolytic enzymes up-regulated to provide energy to RBC