Red Cell Physiology Flashcards

1
Q

Erythropoiesis

A

The process of forming new red blood cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Erythropoietin

A

(EPO)
polypeptide hormone

Released by peritubular cells in kidney as response to hypoxia, e.g.

  • Anaemia
  • Altitude
  • COPD

Increases number of stem cells committed to erythropoiesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why might recombinant EPO be used clinically

A

Treating anaemias associated with renal failure

EPO is released by the kidney

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Reticulocytes and what elevated levels indicate

A

Immature RBC; nucleus extruded and taken up by bone marrow macrophages

Has some dollops of mRNA as cell is still developing

Elevated reticulocyte counts indicates ongoing erythropoeisis

  • bleeding
  • haemolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Average RBC Life Span

A

120 Days

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is RBC lifespan measured (vaguely)

A

Blood sample is taken out and radioactively labelled then injected back; measure rate at which it takes radioactivity decreases at body (should be 120)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

HbA1c

A

Glycated/Glycosylated Haemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Spleen in spherocytosis

A

Genetic Condition;

Abnormal proteins in RBC (spectrin) that breaks down more rapidly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Degradation of RBCs - Where does it occur and what happens to the proteins

A

Occurs in reticuloendothelial system (mononuclear-phagocyte system) of spleen, liver + bone marrow

Proteins degraded and recycled;

  • iron in stores
  • porphyrin (from haem) converted to bilirubin in liver
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Bilirubin; what might elevated levels indicate

A

Yellowish pigment that is made during the normal breakdown of red blood cells

Elevated levels indicate liver disease or elevated RBC breakdown
**Bilirubin causes jaundice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Components of Hb

A

Ferrous Iron (Fe2+) prosthetic groups [Haem] 2 alpha, 2 beta globin polypeptides linked via non-covalent bonds

Haem at centre of protoporphyrin complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Foetal Hb vs Adult Hb

A

Foetuses have Hb containing a2γ2 vs adult which has a2b2

Theres a significant switch at the early part of birth where the foetal Hb is replaced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Best form of iron to get from the diet

A

Fe2+

This is why eating meat doesn’t necessarily give high iron levels (Fe3+)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Iron from diet; drug interaction

A
Some drugs (like tetracycline) can cause chelation of iron and prevent its uptake
(antacids have a similar effect)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does iron from diet metabolise

A

Fe3+ from diet reduced to Fe2+ by syomach acid/is taken up as Fe2+ in the first place

Fe2+ is then converted to Fe3+ in the duodenal cells because god knows why
It is then made into ferritin

Iron is delivered to bone marrow by transferring and stored as ferritin

Incorporated as Hb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Ferritin

A

Blood protein that contains iron; used to measure the body’s iron stores

17
Q

Iron recycling

A

Very efficient; 90% from breakdown of RBCs in liver/spleen

Iron uptake in guts increased when iron deficient; erythroid regulator from bone marrow & an iron stores regulator

18
Q

Two common causes of anaemia

A

Gastrointestinal Bleeding

Menstruation

19
Q

How is Hb allosteric

A

When first O2 binds, a conformational change that increases the affinity of another subunit to O2, followed by another comformational change in the same protein

4th O2 binds approx 300x more readily than 1st

20
Q

Oxygen Dissociation Curve

A

y-axis is percentage saturation of oxygen
Think of x axis as concentration

Not a linear relationship between oxygen saturation and concentration

When first O2 binds, allosteric nature causes change in the molecule; a plateau is eventually caused as a result of maximum saturation (in lungs)

Venous blood is approx 80% saturated believe it or not

21
Q

What happens during exertion in terms of the oxygen dissociation curve

A

Say you start running; your tissues have a low partial pressure of oxygen so they have a massive offloading as they go down the steep part of the curve

The cells have their partial pressure of O2 dropping (O2 is consumed due to respiration); dramatic decrease in saturation so the Hb has to give up its O2

22
Q

Maternal vs Foetal Oxygen Dissociation

A

Foetus has much higher affinity so O2 diffuses from mother’s blood to foetal blood

23
Q

Bohr Effect

A

Acidity enhances O2 release from Hb (CO2 increases blood acidity)

Increasing CO2 at constant pH also lowers Hb’s O2 affinity

Thus O2 is more readily given up to metabolically active tissues (which produce H+ and CO2)

(Right curve is the effect of CO2 released from muscles during exertion)

24
Q

2,3-Diphosphoglycerate (DPG)

A

Present in RBCs at same molar conc as Hb

Reduces O2 affinity of Hb; in its absence, Hb would yield little O2 to tissue

DPG binds to deoxyhaemoglobin to shift equilibrium so that oxyhaemoglobin is more likely to readjust (le chateliers), reducing O2 Binding

DPG increased when arterial O2 reduced chronically (e.g. at altitude, severe COPD), so O2 more readily liberate to tissues

25
Q

2,3 DPG in foetus

A

Foetal Hb does not bind DPG, hence higher O2 affinity

26
Q

Carboxyhaemoglobin

A

Hb has much greater affinity for CO than O2; so if exposed

e.g. via smoking, CO binds irreversibly to Hb to form carboxyhaemoglobin

Tissue becomes starved of O2

CO - Smokers have high levels of CO-Hb

27
Q

Methaemoglobinaemia

A

Iron in Ferric (Fe3+) not ferrous (Fe2+) state

Cannot carry O2

Patient may be cyanosed or anoxic

Caused by Hereditary lack of G6P Dehydrogenase which keeps Hb in reduced state

May be caused by drugs, e.g. antimalarials through oxidant stress

28
Q

CO2 transport in blood - Cl shift

A

10% dissolved in plasma
30% bound to Hb (forming carbaminohaemoglobin)
60% as HCO3- (important in pH)
(don’t memorise)

Catalysed by carbonic anhydrase in RBC
CO2 + H2O –> HCO3- + H+

Hb buffers H+ to modulate pH

HCO3- may leave RBC , Cl- enters (Chloride shift) to maintain charge