RBC Physiology Flashcards
Are are the 2 main components of blood?
Cells + liquid
What is the liquid component of blood called?
Plasma
What are the 3 main blood cell types? Which is commonest
Red cells (commonest)
White cells
Platelets
What is the term for blood cell production?
Haematopoiesis
What sort of stem cell produces blood cells?
Pluripotent - capable of any cell type
At birth where does haematopoiesis occur?
Liver, spleen, bone marrow
Where does haematopoesis occur in a child?
Bone marrow - decreasing number of active sites
Where does haematopoiesis occur in an adult?
Bone marrow of skull, sternum, pelvis, proximal femur
What are the 2 main progenitors in the haematopoietic tree?
Lymphoid and myeloid
What cell type do both lymphoid and myeloid progenitors produce?
Dendritic cells
What cell types do lymphoid progenitors give rise to?
T cells
B cells
NK cells
What cell types do myeloid progenitors give rise to?
Erythrocytes Platelets Mast cells Granulocytes Macrophages
Put these stages of erythropoiesis in order:
- Reticulocyte
- Pronormoblast
- Basophilic normoblast
- Orthochromatic normoblast
- Erythrocyte
- Polychromatophilic normoblast
Erythropoiesis:
- Pronormoblast
- Basophilic/ early normoblast
- Polychromatic/ intermediate normoblast
- Orthrochromatic/ late normoblast
- Reticulocyte
- Erythrocyte
Which statements are true about reticulocytes:
- Smaller that mature erythrocyte
- Have a nucleus
- Contain RNA remnants
- Hypochromatic
- Exist for a few days
- Have just left the bone marrow
Which statements are true about reticulocytes:
- Smaller that mature erythrocyte FALSE LARGER
- Have a nucleus FALSE
- Contain RNA remnants TRUE
- Hypochromatic FALSE POLYCHROMATIC
- Exist for a few days TRUE
- Have just left the bone marrow TRUE
Name 3 causes of a raised reticulocyte count
Haemolysis
>12 hours after acute blood loss
Following Fe supplement in Fe deficiency
In a patient with a raised reticulocyte count, what tests are useful for determining the cause?
Look for Hb breakdown products
Seen in haemolysis
When do normoblasts loose their nucleus?
When optimal Hb content
Where are normoblasts found?
In the bone marrow
What is the consequences of a RBC having no nucleus?
Can’t divide
Can’t replace damaged protein
Limits lifespan
Fits more Hb in
What term describes the shape of a RBC? What is the importance of this shape?
Biconcave
Can withstand high arterial pressure
Contains Hb
>SA for gas exchange
What are 3 functions of RBCs?
Delivers O2
Hb H+ buffer
Transport CO2
What is the name of the enzyme that generates bicarbonate?
Carbonic anhydrase
Where is Epo produced? And in what circumstances?
By kidneys
If they sense hypoxia
What effects does Epo have?
Stimulates erythroid hyperplasia to increase marrow activity
Why is energy production in the RBC limited?
No mitochondria
How do RBCs produce energy?
Glycolysis
AKA Embden-Meyerhof pathway
What are the net products of glycolysis?
ATP + NADH
What is the function of NADH in RBCs?
Prevents Fe2+ oxidation to Fe3+ metHb, can’t carry O2
What is the Rapapoport-Lubering shunt?
Alternate route for glucose to pyruvate via 2,3-DBG
when does it happen? maybe in oxidative environment?
What is the allosteric effect?
When 1 oxygen binds to a Hb subunit the shape changes to increase the affinity for O2
Where are old / abnormal RBCs removed? What cell type is responsible for this?
Spleen
Macrophages
Macrophages recycle old red cells. What are the globin chains recycled to?
Amino acids
Macrophages recycle old red cells. What are the heme chains recycled to?
Brown to iron + bilirubin
Iron transferred back to barrow erythroblasts
Heme converted to bilirubin
What are the intermediate steps of heme conversion to bilirubin?
Heme to porphyrin to bilverdin to bilirubin
What happens to bilirubin after it leaves the spleen?
Conjugated in liver, then excreted in bile
Reactive oxygen species are made in a ______ environment
Oxygen rich
Reactive oxygen species free radicals oxidise things they shouldn’t such as …
DNA
Name 2 free radicals
Hydrogen peroxide
Superoxide
What thing removes the free radical hydrogen peroxide?
Glutathione and G6PD enzyme
What thing remove the superoxide free radical?
Superoxide dismutase enzyme
CO2 transport:
30% as _____
60% as _____
10% as _____
30% carbamino-Hb
60% bicarbonate
10% dissolved
What cycle is B12 responsible for?
Methionine cycle
What cycle overlaps with the methionine cycle?
Folate cycle
B12 and folate both aid in what in the RBC?
DNA synthesis
What are the main components of Hb?
Haem + globin chain
What is a haem group made of?
Iron + porphyrin ring
What is the function of iron in Hb?
Binds oxygen
What are the globin chains in adult haemoglobin HbA?
2 alpha chains
2 delta chains
What are the globin chains in fetal haemoglobin HbF?
2 alpha
2 gamma
How does fetal haemoglobin differ in function from adult haemoglobin?
Increased saturation at same partial pressure of oxygen
What effect does chronic anaemia have on the oxygen Hb dissociation curve? What molecule in the RBC is attributed to this?
Shifts curve right (double check this)
Increased 2,3-DPG
How many molecules of oxygen can 1 molecule of Hb carry?
4
Free haemoglobin binds to Fe3+ producing what?
MetHb which can’t carry O2
What are the types of granulocyte? Which is commonest?
Neutrophil commonest
Eosinophil
Basophil
What are the 2 states of iron in the most?
Fe2+ (ferric)
Fe3+ (ferrous)
What are the location of iron within the body?
Most in Hb Parenchyma Myoglobin Enzymes Macrophages Marrow
Where is iron absorbed?
Duodenum
What food interferes with Fe absorption?
Tannins in tea
others
Iron in the liver is bound to what protein?
Ferritin
Iron in macrophages is bound to what protein?
Ferritin
What protein is responsible for transporting iron throughout the circulation?
Transferrin
What protein is responsible for Fe transport out of cells to transferrin?
Ferroportin
Where does transferrin transport iron from? Where to?
From macrophages / intestine / hepatocyte
To tissues expressing transferrin receptors (erythroid marrow)
Serum ferritin is raised in malignancy and sepsis since it is an ______
acute phase protein
What protein is a negative regulator of Fe uptake? What is its function?
Hepcidin
Degrades ferroportin
What effect does iron deficiency have on hepcidin?
Decreases
Where is hepcidin produced?
Liver
