Anaemia (Fe absorption, B12, folate) Flashcards
Mean cell volume
Average size of RBCs
Mean corpuscular volume
Average mass of haemoglobin per RBC
Haematocrit
Proportion of blood containing RBCs
Macrocytic anaemia
Overly large RBCs, not enough normal sized cells
Microcytic anaemia
Small RBCs and not enough normal cells
Anaemia symptoms
- Fatigue, loss of energy
- heart palpitations
- SOB
- Difficulty concentrating
- Dizziness
- Pale skin
- Leg cramps
- Insomnia
What is anaemia?
Decreased Hb, decreased erythropoiesis
Increased RBC destruction
How long do erythrocytes last and where are they broken down?
120 days, spleen
How does O2 bind to RBCs
- Fe sitting below porphyrin ring
- 4 subunits - 2 alpha and 2 beta
- Each has a haem group
- Each Fe binds to one O2 molecule
Which four molecules can bind to Hb
O2, CO2, CO and NO
When is erythropoietin produced?
Fall in oxygen to kidneys - cells lining kidneys
Indications of anaemia on blood test
Hb, MCV, HCHC
Why does sickle cell anaemia cause splenomegaly?
Breaks down so many RBCs
Iron deficiency
- Low iron leads to low Hb production
- 2 forms - dietary iron in the form of heme (meat, blood) or non-heme (leafy green veg)
- Normally loss of iron = faeces and menstrual blood loss
- Abnormal blood loss = haemorrhage and chronic blood loss
- Iron comprises O2 binding factor in haemoglobin and its deficiency limits O2 carrying capacity of blood
Folate deficiency
- Reduced intake
- Increased demand
- Malabsorption
- Drugs
- Stores last 4 months
- Comes from green veg, nuts, liver
- Methotrexate damages folic acid pathway
B12 deficiency
- Reduced intake (vegan diet)
- Reduced intrinsic factor
- Reduced absorption
- Functional deficit (NO use)
- Stores last 4-7 years
- Meat, fish, dairy but not plant
Microcytic anaemia causes
Iron deficiency
Macrocytic anaemia causes
B12/folate
Impact of B12 on dorsal columns
Causes neuronal damage
How does pernicious anaemia occur?
Vit B12 malabsorption is basis
Atrophic gastric mucosa fails to secrete normally
Lack of intrinsic factor from cells of gastric glands
No binding of B12 to intrinsic factor
B12 isn’t protected from digestion by GIT enzymes and doesn’t bind to receptor sites in terminal ileum
Failure to absorb B12 from GIT
How are vitamins normally absorbed in the small intestine?
Carrier-mediated transport or passive diffusion
How is vitB12 absorbed?
It forms an acid-resistant complex with intrinsic factor in the stomach
The complex binds to specific receptors on mucosal cells in the terminal ileum, where B12 is absorbed via endocytosis
