RBCs And Haemoglobin (haematology, Physiology) Flashcards
What is the main function of RBCs
They carry oxygen from the lungs to systemic tissue and carbon dioxide to the lungs.
Explain how RBCs transport carbon dioxide to lungs (8)
•Co2 diffuses from the peripheral tissues into the systemic capillaries.
•Only 7% of CO2 remains in plasma.
•About 25% of the CO2 binds to haemoglobin to form carbaminohaemoglobin.
•70% of the CO2 react with water to form CA which dissociate to form bicarbonate and hydrogen ions, the hydrogen ions are buffered by haemoglobin.
•The bicarbonate moves out of the RBCs in exchange for Chloride ions.
•In the lungs, dissolved CO2 diffuses out of the plasma into the alveoli.
•By the law of mass action, CO2 unbinds from haemoglobin and moves out of the RBCs.
•The CA reaction reverses, pulls bicarbonate into the RBCs and convert it back to CO2.
Which enzyme catalyses the reaction btwn water and CO2?
Carbonic anhydrase enzyme
Why do RBCs lack mitochondria?
Because RBCs carry oxygen, and cellular respiration in the mitochondria utilises oxygen. So if there is mitochondria in the RBCs the process will utilise the oxygen and decrease the oxygen supplied to tissues.
By which process do RBCs generate ATP?
Glycolysis
What are the normal haematocrit values?
Males- 46%
Females- 42%
What happens when an erythrocyte is placed in:
1. A hypertonic medium
2. A hypotonic medium
- It shrinks, but the rigid cytoskeleton remains and form a spiky surface, we now refer to it as a crenatus.
- It swells and lose its biconcave disc shape.
In which case does the RBC change its shape?
In a sickle cell disease
During the metabolism of RBCs which molecule is produced by the reactions associated with glycolysis?
2,3-bisphosphoglycerate
What do we call the protein found in RBCs?
Haemoglobin
Normal values for haemoglobin levels
Males: 14-18 g/dL
Females: 12-16 g/dL
What forms when haemoglobin binds to:
1. Carbon dioxide
2. Oxygen
3. Carbon monoxide
- Carbaminohaemoglobin
- Oxyhaemoglobin
- Carboxyhaemoglobin
What do we call the molecule that forms when haemoglobin has Fe3+?
Methemoglobin
Explain the process of formation and metabolism of hemaglobin (6)
-Fe is ingested in diet.
-Fe is absorbed in the small intestines by active transport.
-Fe is transported by transferrin to the bone marrow where is binds to globin and forms haemoglobin.
-Haemoglobin in RBCs in metabolised in the spleen and it forms bilirubin.
-Bilirubin and other metabolites can be excreted in kidney through urine or in large intestines through faeces.
-Liver metabolises bilirubin and excretes it in the bile.
-Excess iron is stored in the liver as ferritin.
Three stages of erythropoiesis in foetal life
Mesoblastic stage
Hepatic stage
Myeloid stage
Factors necessary for erythropoiesis
•General factors such as erythropoietin, thyroxine, vitamins and haematopoietic growth factors.
•Factors necessary for the production of haemoglobin such as iron.
•Maturation factors such as vit b12, folic acid and intrinsic factor of castle.
Lack of vit b12 during erythropoiesis causes what?
Pernicious anaemia
How is haemoglobin recycled?
-Macrophages in the liver, spleen and bone marrow engulf RBCs.
-The Hb molecules are removed from hemolyzed (ruptured) RBCs.
-The Hb is broken into components.
- Only the iron of each heme unit is recycled.
What is hemogluburia and what can cause it?
Excess haemoglobin in urine, can be caused by abnormally high hemolysis in bloodstream.
What is hematuria and what causes it?
Whole RBCs in urine and it is caused by kidney or blood vessel damage.
How is iron metabolized and excreted? (3)
Iron is removed from each heme unit forming green biliverdin.
Biliverdin get converted to orange-yellow bilirubin.
Bilirubin is excreted by the liver in bile.
What does excess bilirubin cause?
It causes jaundice.
What are the physiological causes of elevated RBC levels? (6)
-Age and gender
-After meals
-Higher altitude
-Emotional conditions
-Increased environmental temperature.
-Muscular exercise
What are the physiology causes of low levels of RBCs? (3)
-Increased barometric pressure
-During sleep
-Pregnancy
Pathological causes of variations in RBC number(4)
Primary polycythaemia: Polycythaemia vera
Secondary pathologies
-Chemical poisoning
-Congenital heart disease
-Emphysema
What do we call RBCs that have:
1. Small size
2.Large size
3. No uniform size
- Microcytes
- Macrocytes
- Anisocytes
What causes the formation of:
1. Microcytes
2. Macrocytes
3. Anisocytes
- Iron deficiency anaemia
- Megaloblastic anaemia
- Pernicious anemia
What are the variations in the shape of RBCs? (5)
Spherocytosis
Poikilocytosis
Ellipticytosis
Crenation
Sickle cell
What are the variations in RBC structure, explain.
Punctuate basophilism- Dots of basophilic materials.
Ring- Rings of basophilic material in the periphery of cell.
Howell-Jolly bodies- Nuclear fragments in the ectoplasm.
Disorder caused by reduced hematocrit or haemoglobin?
Anaemia
Three classifications of anaemia according to what causes it.
Hemorrhagic anaemia- caused by acute or chronic loss of blood.
Haemolytic anaemia- premature rupture of RBCs.
Aplastic anaemia- Destruction or inhibition of red bone marrow.
What causes:
1. Iron-deficiency anaemia
2. Pernicious anaemia
- Usually blood loss which causes reduced levels of iron in the body.
- Vit B12 deficiency secondary to intrinsic factor deficiency.
What causes abnormal haemoglobin?
Thalassaemia and sickle cell anaemia
