Red cells Flashcards
What are the precursors to red blood cells known as?
Multipotent haemopoietic stem cells
By what process do blood cells arise?
Haemopoiesis
What are the essential characteristics of haemopoietic stem cells?
Being able to self renew
- Some daughter cells remain as HSCs so the pool of HSCs is not depleted
Differentiate to mature progeny
- Other daughter cells differentiate and form different cells
What is eryhtropoiesis?
The development of red cells
What benefit does red cells being concave give them?
It helps in maneuverability through small blood vessels to deliver oxygen
What is erythropoeitin?
A growth factor required for the formation of red blood cells
Required in eryhtropoeisis
A glycoprotein produced in the kidney in response to hypoxia - juxtabular interstitial cells
Stimulates bone marrow to produce more RBCs
What is haemaglobin A made up of?
4 subunits, 2 alpha chains and 2 beta chains
What are haem groups made up of?
A ferrous ion, Fe2+, held in a ring known as porphyrin
Where is iron absorbed?
The duodenum
How are iron levels managed?
No physiological mechanism
Absorption is tightly controlled, 1-2mg absorbed daily from diet
What is hepcidin?
A hormone that inhibits iron absorption
How does an increased erythropoeitic activity effect hepcidin levels?
Increased erythropoeitic activity -> increased iron requirement -> decreased hepcidin -> increased iron absoprtion
What are vitamin B12 and folate used for?
The synthesis of dTTP which is needed for the synthesis of thymidine
What does a lack of B12 and folate result in?
Inhibition of DNA synthesis as thymidine cannot be produced
Affects all rapidly dividing cells
dUMP cannot convert into dTMP
What foods can vitamin B12 be gained from?
Meat, Liver and kidney, Fish, Oysters & Clams, Eggs, Milk & Cheese, Fortified cereals
What foods can folic acid be gained from?
Leafy greens, Cauliflower, Brussels sprouts, Liver & Kidney, Whole grain cereals, Yeast, Fruit
How is B12 absorbed?
- Binds to Intrinsic Factor in stomach
2. B12-IF binds to receptors in the ileum - in small intestine
What can cause a B12 deficiency?
Veganism
Inadequate secretion of intrinsic factor - autoimmune disorder
Malabsorption
What happens when red cells are destroyed?
Phagocytic cells in the spleen breakdown red cell
Iron from haem goes to bone marrow to be reused
Bilirubin is excreted in the bile
What is hypochromia?
Where a RBC has a greater area of central pallor than normal
What is polychromasia?
An increased blue tinge to the cytoplasm of a red cell - indicates cell is young
How do you detect young cells in a blood smear?
Stain it with new methylene blue stain as it stains the higher RNA content darker
When may reticulocytosis occur?
After bleeding or red cell destruction
What is poikilocytosis and anisocytosis?
Poikilocytosis - red cells showing more variation in shape than normal
Anisocytosis - red cells showing more variation in size than normal
What are target cells?
Red cells with an accumulation of haemoglobin in the center of the area of central pallor
What is sickle cell caused by?
A person inheriting 2 abnormal beta globin genes
Glutamic acid in position 6 is replaced by an uncharged valine molecule
