Red blood cells- creation, function and destruction Flashcards
Aidan
What is haematocrit?
the packed cell volume or the amount of RBC’s in the total blood volume.
What is generally the make up of the blood in people with anaemia?
less RBC’s in proportion to WBC’s and plasma than usual but normally the same amount of blood volume.
Describe the structure of RBC’s
A biconcave disc with a high surface areas to volume ratio.
What are the main functions of RBC’s?
Transport of O2 and CO2 and maintaining the acid/base balance of the blood.
Brief description of RBC’s?
Bag of Haemoglobin (Hb) and enzymes for glycolysis- unable to divide and create new proteins.
How does bone marrow move from birth to adulthood.
Widespread throughout body after birth but redistributed to the axial skeleton by adulthood.
Name the stroma of the bone marrow
Fibroblasts, macrophages, endothelium and fat cells.
What other cells do red blood cells develop around?
Red blood cells mature and develop around macrophages in the bone marrow
What is the function of the macrophages in the bone marrow?
Macrophages are the main store of iron in the bone marrow and feed this to developing RBC’s.
What is reticulin?
remnants of mRNA left once the nucleus of a maturing RBC has been extruded, removed by the spleen within 1-2 days.
what form must iron be in to be absorbed and used?
ferrous form
when is there a higher need for iron?
During pregnancy/Blood loss
What does hepcidin do in the body?
It regulates iron absorption and release from macrophages- increased in inflammatory disease so less available iron.
What are some causes of iron loss from the body?
Blood sampling, menstrual loss, minor trauma, GI approx 1ml per day, very small amounts in urine/skin shedding.
what is the role of transferrin?
Transport/recycling, transferrin receptors increased when iron is deficient.
What is ferritin?
The insoluble storage form of iron (it is a better measure of iron stores).
What are B12 and folate(folic acid) involved in?
They are important in the production of RBC’s
When is erythropoetin produced?
Tissue hypoxia and anaemia, high altitude and certain epo producing tumours (renal).
What is produced when at low oxygen levels?
erythropoetin (epo).
What is the most important driver of RBC production?
Erythropoetin (epo)
What is spectrin and what properties does it give to RBC’s?
It gives RBC’s their flexibility and ability to return to shape after squeezing through tiny capillaries etc.
What does haem do and where are they found?
It binds to oxygen and one is found per globin chain.
What does haemoglobin need? (adults)
Two alpha chains and two beta chains
What does haemoglobin need? (foetal)
Two alpha chains and two gamma chains
What is Thalassaemia in relation to globin chains?
An inherited defect in globin chain production.
What is sickle cell anaemia in relation to globin chains?
One amino acid change in the beta chain.
What does the glycolytic pathway ending in lactate and pyruvate supply energy for?
Maintaining membrane integrity, Prevent oxidation of enzymes and Fe++, Maintain gradients of of K+ and Ca++
what can cause anaemia by increased haemolysis (increased rate of RBC breakdown).
Enzyme deficiencies e.g; pyruvate kinase.
What will acidosis and increased temperature cause?
will cause more oxygen to be delivered to the cells.
what causes an increase of 2,3 DPG?
Exercise, anaemia and high altitude.
What happens with the buildup of 2,3 DPG?
It works its way in between the globin strands and forces the chains apart to allow more oxygen to be released.
Where is Myoglobin located?
In skeletal muscle.
What is Myoglobin used for?
A ‘last ditch’ store of O2 for immediate use in cases of extreme exertion.
What is the acid-base balance?
The regulation of H+ ions in the body fluids
Why is the acid-base balance important?
Enzymes work optimally at physiological pH, Cell membranes become leaky in acidosis and Neurones become less able to transmit in acidosis and hyperactive in alkalosis.
What are buffer systems used for?
Used to regulate the amount of hydrogen ions in the body by providing a buffer against extreme changes in hydrogen ions
which buffer system accounts for 60% of the available buffer?
Bicarbonate reaction using carbon anhydrase as the catalyst.
Which buffer system accounts for 30% of the available buffer?
Haemoglobin binds to H+ ions after the loss of oxygen and then Hb reacts with CO2 (more H+ ions are buffered and absorbed than are released in this reaction).
What happens as red blood cells age?
Membrane becomes more rigid, loses glycolytic enzymes and neoagents are exposed on the cells surface
Examples of RBC loss or destruction?
Some RBC loss into GI/menstrual loss/into soft tissues and some RBC’s are destroyed within the body
How does the spleen/liver recycle RBC’s?
- Free Hb “mopped up” by haptoglobin- cleared by liver. (Any excess can appear in urine).
- Globin chains broken up into amino acids
- Iron bound to transferrin and returned to macrophages
- Porphyrin ring becomes bilirubin- bound to albumin and “conjugated” to glucuronide- excreted in bile
