Red Blood Cells (RBC) Flashcards
How much Blood Volume a normal 70kg adult contain?
5L, of which 40% cells and 60% plasma
Describe anaemia and polycythaemia
Anaemia is having a lower percentage of blood cells compared to normal. Polycythaemia is having a higher percentage of blood cells compared to normal.
What is the life span of RBC?
100 days
Why are RBC subject to high pressures?
Because they are squeezed through narrow capillaries every minute
Describe the appearance of a RBC?
Has a biconcave disc appearance and no nucleus
What makes RBC flexible?
Because they have no nucleus, thus increase surface area
What maintains the gas exchange in RBC? and what makes that gas exchange fast?
Gas exchange is faster because of the high surface area of a RBC, and it is maintained by a complex cytoskeletal system
Why RBC are unable to divide?
Because they have no nucleus or ribosomes
What is the main function of RBC?
Transport oxygen and carbon dioxide, and maintain acid and base balance. This is by maintaining membrane integrity and preventing oxidation of haemoglobin
Where does haemopoiesis occur?
In bone marrow.
What is extramedullary haemopoiesis?
A haemotological disease that occurs when haemopoiesis occurs in the spleen or liver
What does bone marrow stroma contain?
Macrophages, endothelial cells, fibroblasts, fat cells and associated stromal proteins
What is used to stain macrophages in marrow?
Peroxidase - stains brown
What are the growth factors that drive maturation?
Interleukin 3 Erythropoitetin (biggest factor) Androgens Thyroxine Growth hormone
Define reticulocytes
an immature red blood cells without a nucleus
Define reticulin
Remnants of mRNA left once the nucleus of maturing RBC has been extruded (often removed by spleen in 1-2 days)
Why is reticulin useful?
It is a useful measure of marrow response to anaemia or treatment
How is reticulin stained?
By new methylene blue on slide, or an automated count
What is the normal level of Iron in an adult?
3000-5000mg
How much Iron does a daily diet contain? How much is actually absorbed, and in which form?
10-20mg. Only 1-2mg is absorbed in ferrous form
In what cases more absorption of Iron is necessary?
Blood loss or pregnancy
Where is the ferrous form of Iron transported to?
Duodenal enterocytes
What is the regulator of Iron absorption and the release from macrophages?
Hepcidin (in gut)
What are the mechanisms to excrete Iron?
There are no mechanisms
What causes Iron loss?
Blood sampling Minor trauma Menstrual loss (period) Very small amounts in urine/skin shedding GI (1mL per day)
How is Iron transported
Transferrin and Ferritin
When are Transferrin receptors increased?
During Iron deficiency
What is the best measure of Iron stores?
Ferritin
What is the daily requirement of Folate and how much does a diet contain?
- 1mg
0. 25mg
What contains folic acid and where is it absorbed?
Green vegetables and fruits
It is absorbed in the upper small intestine/bowel
What can cause deficiency in folic acid?
Poor intake, poor absorption and increased need
What is the daily requirement of Cobalamin and how much does a diet contain?
1mg
5mg
What contains B12 and where is it absorbed?
In animal derived products
Absorbed in terminal ileum
How is B12 moved into the terminal ileum?
Gastric parietal cells produce intrinsic factor that binds to B12 and stays in gut and moves into terminal ileum. Transported on transcobalamin II via protal circualtion liver
What can cause deficiency in B12?
Vegan diet or perinicous anaemia
What can cause gastric atrophy?
Antibodies to intrinsic factors
What catalyses the conversion of uridine to thymidine?
The change from 5 THF to THF and then into 5,10 methelene THF, which is all started by B12
What is the role of Erythropoietin?
It controls the rate of RBC production in blood marrow
What produces Erythropoietin?
The kidney (90%) and the liver (10%)
How is Erythropoietin regulated?
The body has no stores of Erythropoietin, and its regulation is at the gene transcription level
How is Erythropoietin switched on?
Tissue hypoxia or anaemia
High altitude
Epo producing tumours (e.g. Kidney)
What is Erythropoietin useful for as a recombinant drug?
Renal anaemia and myelodysplasia
What gives the RBC membrane its rigid shape?
The two strands of Sceptrin
Describe the RBC membrane
Lipid bi-layer with protein bound into it
Describe what makes a Haemoglobin
Four globin chains and four haem molecules.
2 Alpha-like chains (Ch 16), Zeta (Early foetal) then Alpha
2 Beta-like chains (Ch 11), Epsilon then Gamma, then Delta, then Beta
What makes a Haemoglobin for an adult?
2 Alpha and 2 Beta
What makes a Haemoglobin for an early foetal?
2 Alpha and 2 Gamma
Define Thalassaemia
An inherited defect in globin chain production
Define Sickle Cell disease
One amino acid change in beta chain
What is Myoglobin?
In skeletal muscle. It is a store of Oxygen for immediate use.
Describe the structure of Myoglobin
One haem unit, one globin chain
How pH is measured?
pH is measured on log scale
Why is acid-balance important?
Enzymes work optimally at physiological Ph
Cell membranes become leaky in acidosis
Neurones become less able to transmit in acidosis (hyperactive in alkalosis)
State the buffer systems of the human body
- Bicarbonate (60% of buffer capacity)
- A decrease in pH/increase in H+ will drive equation to the left - Haemoglobin (30% of buffer capacity)
- H+ combines with Haemoglobin after loss of Oyxgen and Low pH decreases Haemoglobin affinity for O2
What is the catalyst for the bicarbonate buffer system?
Carbonic Anhydrase (CA)
What is the equation for the bicarbonate buffer system?
CO2 + H2O —> H2CO3 —> H+ + HCO3-
What is the equation for the haemoglobin buffer system?
CO2 + Hb —> HbCOO- + H+
What causes RBC loss or destruction?
As RBC age, membrane becomes more rigid and the loss of glycolytic enzymes increases and neoantigents exposed on cell surface
Some are lost from GI tract/into soft tissues/menstrual loss
Some RBC destroyed within body
