Haematology (asthma)

Question 1

How to prevent haemolytic disease of the new born?

Answer 1

anti-D immunisation with anti-D immunoglobulin

binds to infant cells and prevents mother from raising antibodies

Question 2

What is erythropoiesis controlled by?

Answer 2

erythropoietin - polypeptide hormone

Question 3

What releases erythropoietin and when?

Answer 3

peritubular cells in kidney in response to hypoxia (low O2)

eg. anaemia, at altitude, COPD

Question 4

What does erythropoietin do?

Answer 4

increases number of stem cells committed to erythropoiesis

Question 5

What is recombinant erythropoietin (EPO) used for?

Answer 5

clinically: treat anaemias associated with renal failure

open to abuse by athletes - increase blood viscosity

Question 6

What is a reticulocyte?

Answer 6

immature RBC

Question 7

What happens to reticulocytes during erythropoiesis?

Answer 7

maturation
nucleus extruded and taken up by bone marrow macrophages
mRNA in reticulocyte allows Hb to still by synthesised
increase in reticulocyte = increase in EPO and erythropoiesis

Question 8

Life span of RBC

Answer 8

120 days

Question 9

Structure of haemoglobin

Answer 9

tetrametric: 4 globin chains
haem: ferrous iron (Fe2+) at centre of protoporphyrin complex
globin chains linked by non-covalent bonds, each are a polypeptide with haem prosthetic group

Question 10

Structural difference between adult and fetal Hb

Answer 10

adult: α2β2 subunits
fetal: α2γ2

Question 11

Stages of iron metabolism

Answer 11

Fe3+ reduced to ferrous iron (Fe2+) by stomach acis
Fe2+ -> Fe3+ produced by mucosal cells of duodenum binds to apoferritin to produce ferritin
release iron into blood with transferrin
delivers iron to bone marrow
iron in Hb

Question 12

Role of ferritin

Answer 12

stores iron and releases it in a controlled fashion

Question 13

Role of transferrin

Answer 13

deliver iron from absorption centers in the duodenum and white blood cell macrophages to all tissues

Question 14

When is iron uptake in the guts increased?

Answer 14

when iron deficient

erythroid regulator from bone marrow and iron stores regulator involved

Question 15

How is O2 transported in the blood?

Answer 15

RBCs carry O2 from lungs to tissues

4 O2 per Hb, bind to Fe2+

Question 16

Describe oxygen dissociation curve

Answer 16

sigmoidal curve
low ppO2 - low O2 sat, high dissociation
high ppO2 - high O2 sat, low dissociation

Question 17

How does a fetal dissociation curve differ to an adult one?

Answer 17

much steeper

much higher association of O2 at lower pp, fetal Hb has much higher affinity for O2

Question 18

Describe the Bohr effect

Answer 18

acidity enhances release of O2 from Hb
increasing Co2 at constant pH lowers Hb O2 affinity
therefore, O2 more readily given up to metabolically active tissues which produce H+ and CO2
shift to right of normal O2 dissociation curve

Question 19

Effect of 2,3-diphosphoglycerate (DPG) on O2 carriage

Answer 19

reduces Hb affinity for O2
DPG binds to deoxyhaemoglobin to shift equilibrium, reducing O2 binding
if absent, Hb would yield little O2 to tissues

Question 20

Effect of DPG on fetal Hb

Answer 20

no effect as fetal Hb is unable to bind to DPG, therefore have a higher affinity

Question 21

When is DPG increased?

Answer 21

arterial O2 chronically reduced, so O2 more readily liberated to tissues
eg. at altitude, severe COPD

Question 22

Why is inhalation of CO dangerous?

Answer 22

Hb has a much greater affinity for CO than O2, forming carboxyhaemoglobin
CO-Hb does not readily dissociate and therefore less O2 binding and transported to tissues
tissues starved of O2

Question 23

What is methaemoglobinaemia?

Answer 23

rare condition in which the haemoglobin iron is in the oxidised/ferric state (Fe3+) and cannot reversibly bind oxygen
symptoms: cyanosed, anoxia symptoms (dizziness, tachycardia, repiratory distress)

Question 24

Possible causes of methaemoglobinaemia

Answer 24

hereditary lack of glucose-6-phosphate dehydrogenase, which keeps Hb in reduced state
drugs eg. antimalarials

Question 25

How is CO2 carried in the blood?

Answer 25

10% dissolved
30% bound to Hb to form carbaminohaemoglobin
60% as HCO3- (may leave, Cl- enters to maintain resting potential)
CO2 + H2O -> HCO3- + H+
catalysed by carbonic anhydrase in RBC