Lecture 2: RBCs and Hb

Question 1

Normal RBC?

Answer 1

• discoid allowing flexibility and increased surface area
• 7um diameter
• No nucleus or RNA
• Hb and O₂ transport

Question 2

Shape + deformability allow/due to?

Answer 2

Allows gas exchange and movement and is determined by membrane and cytoskeletal proteins

Clinical: abnormalities of the membrane can result in shortened lifespan (eg. hereditary spherocytosis)

Question 3

RBC role with Hb?

Answer 3

Keeps Hb in a reduced state and maintains osmotic equilibrium. Glycolytic pathways produce ATP - maintains osmotic equilibrium

HMP shunt produces NADPH - keeps Hb reduced

Clinical: inherited defects in enzyme pathways leads to haemolysis (shortened red cel survival) - (eg. G6PD enzyme deficiency)

(fava beans put increased oxidative stress and can cause acute haemolysis in G6PD deficient patients)

Question 4

2 outlines for anaemia?

Answer 4

Low Hb caused by:

1. deficiency of iron resulting in reduced haem produciton
2. impaired production of globin chains (thalassemia)

Question 5

Erythroid precursor cells (morphological stages)

Answer 5

As they mature there are changes with this differentiation:

• progressive increase in Hb
• proliferation/amplification
• Chromatin clumps and nucles eventually extruded
• loss of RNA

clinically:

Nucleated RBC in the blood are often seen in mylofibrosis and other conditions.

If you have been under stress like surgery then there will be an increase reticulocyte (still have RNA) in the blood. Non-invasive, indirect way of measuring bone marrow activity/erythroid production.

Question 6

How long after starting Iron supplements having effect?

Answer 6

Can take around 7-10 days to start producing Hb and so around 14-16 days before you will actually see a difference.

Question 7

Erythropoietin and its regulation?

Answer 7

A glycoprotein produced in the Kidneys and responds to low oxygen tensions.

A feedback loop: Peritubular cells in outer cortex that are sensitive to hypoxia. Reduced O2 to these cells will result in increased EPO production. Acts on the later stages and RBC precursors in the marrow and increases committment along with increased release of reticulocytes into the blood.

Question 8

Effects of EPO?

Answer 8

EPO binds to the erythropoietin receptor to icrease red blood cell production:

1. Stimulation of BFU-E and CFU-E
2. increased haemoglobin synthesis
3. reduced rbc maturation time
4. increased reticulocyte release

Results in increased haemaglobin, therefore increased oygen delivery. Used for: anaemic patients and renal failure patients.

Question 9

RBC destruction?

Answer 9

Cells become less deformable and need to be removed in the liver and spleen. Breakdown of red blood cells with release of Hb

Haem is broken to iron that goes to the bone marrow and the protoporphyrin ring forms bilirubin - liver - bile. (this unconjugated bilirubin can cause jaundice)

Question 10

Anaemia is defined as?

Answer 10

• Hb lower than normal for the age and sex of patient (not about number like all others)
• haematocrit = % of RBC to total blood and correlates to amount of Hb in the blood
• depends on age and sex and is a range
• Presents with a mixture, including: Tiredenss, fatigue, SOB

Responds via:

• increase CO (SV and HR)
• shift to the right in the Hb dissociation curve

Question 11

Classification of anaemia?

Answer 11

Physiologic: Impaired production versus blood loss/ reduced survival of cells

Morphological: size of cells (microcytic or macrocytic)