blood 1

Question 1

Erythrocytes - RBCs

Answer 1

• Biconcave disc (8um x 1-2.5um, high SA:vol ratio)
• No nucleus in mammals
• Can be deformed (helps when getting through tight spaces)
• Rouleaux formation (RBCs stack up in a line when protein conc in plasma is too high)
  
  • Not good: cannot deform well
• High carbonic anhydrase + membr permeability to anions (specifically Cl- + HCO3-)
• Hemoglobin + gas binding (particularly O2)
  
  • 4 binding sites on hemoglobin, 270mill hemoglobin per RBC (= lots of oxygen)

Question 2

Erythropoeises

Answer 2

In BM
- Released as reticulocytes
- Once erythrocytes are released from BM, mature in 1-2 days
- 2e11 RBCs replaced per day
- Development from HSC occurs as a result of factors in env, particularly EPO and IL-3
* look at diagram

Question 3

Hemolysis

Answer 3

Blood watered down: hypotonic ECF (low solute)
Water enters RBC
Swelling and bursting

Question 4

Crenation

Answer 4

Too much solute in blood: hypertonic ECF
H2O leaves cell
Cell shrivels - can lead to cell death but is reversible

Question 5

Factors involved in erythropoiesis

Answer 5

1. TIssue oxygen
   
   • Decr O2 from anything leads to incr RBC production
2. Erythropoietin (EPO)
   
   • Incr survival rates thru stages of prolif. (reduces apoptosis)
3. Cytokines (IL-3)
4. Metals:
   
   • Iron: biosynthesis of heme
   • Copper: Component of ceruloplasmin (helps oxidate Fe2+ -> Fe3+)
5. Folic acid and vit B12
   
   • Coenzymes in DNA synth - imp for high rates of cell division
6. Sex steroids:
   
   • Testosterone: incr erythropoiesis
   • Estrogen: decr erythropoiesis

Question 6

Regulation of erythrocyte production

Answer 6

EPO produced and released by kidney which senses hypoxic states
Low O2 sensed by kidney -> hypoxia inducible factor (HIFalpha and beta) -> stimulates production and release of EPO by kidney

Question 7

Causes of hypoxia

Answer 7

Loss of blood
loss of pulmonary function
loss of cardiac function
loss of erythrocyte oxygen carrying capacity (not enough iron, anemia)

Question 8

EPO regulation of erythropoiesis

Answer 8

BFU-E and CFU-E are responsive to EPO stimulation
EPO incr, incr progenitor survival

Question 9

Injecting epo

Answer 9

Incr hematocrit + RBCs (polycythemia, too much hematocrit)
More O2 delivered to muscles, improved aerobic capacity (VO2 max) and endurance
Risks:
- Incr blood clotting