Erythropoiesis Flashcards
What percentage of blood is made up of Erythrocytes
90%
What other cells are present in blood
Leucocytes
Thrombocytes (platelets)
Why do erythrocytes have a biconcave disc shape
Increases surface area by around 20-30% increasing carrying capacity
What will failure of Na+ movement across the erythrocytes cell membrane
Leads to swelling and loss of the normal biconcave disc morphology
Describe dog erythrocytes
uniform in size, with a concave shape
Describe cat erythrocytes
smaller
anisocytosis (variation in size)
less concave
Describe the appearance of horse erythrocytes
Have a rouleaux formation (clustering of RBCs in standing blood)
Describe the apperance of ruminant erythrocytes
crenation (spiky)
variation in size
Describe the apperance of camelid erythrocytes
elipsoid in shape
What are some defining features of avian and reptile erythrocytes
- Nucleated
- Larger
immature erythrocytes may be rounded - cells can lose their nucleus and be termed erythroplastids
Why are erythrocytes so metabolically active
Energy is require to maintain the electrochemical gradient across the plasma membrane and of haemoglobin molecules
How do erythrocytes derive energy
By anaerobic metabolism of glucose (avoid consumption of O2 they are carrying)
What are the main roles of erythrocytes
- Transport of O2 from lungs to cells
- Transport of CO2 from cells to lungs
How is CO2 transported in the blood
Dissolved in plasma, bound to globin, or as bicarbonate ions in plasma
What percentage of erythrocyte protein is haemoglobin
95%
Describe haemoglobin
Made of 4 polypeptide subunits (2 infection all alpha ones and 2 identical beta ons), and is a water soluble globular protein.
A central haem group is found in the each of the polypeptide subunits, contains an iron atom to bind O2
What does haemoglobin do in areas of high oxygen concentration
Globin releases CO2 and iron binds to O2 (oxyhaemoglobin)
What does haemoglobin do in areas of low oxygen concentraion
O2 released and binds to CO2 (carbaminohaemoglobin)
What is released in hypoxic tissues to facilitate release of O2 from erythrocytes?
2,3-diphosphoglyceride (a carbohydrate)
What happens if haemoglobin binds nitric oxide
Causes dilation of the blood vessels
What compound has a greater affinity for haem than oxygen and can be fatal?
Carbon monoxide
What is haematopoiesis?
formation of blood cells
What is erythropoiesis?
production of red blood cells
Where does haematopoiesis occur?
red bone marrow and spleen
Which organ is an important haematopoietic organ in fish?
The kidney
What is require for the formation of erythrocytes
Protein, Iron, Copper, Folic acid, Vitamins (B2, B6, B12)
What can a reduction of iron have of erythropoiesis?
Reduces the formation of new RBCs
What is erythropoietin (EPO)?
hormone that stimulates RBC production
Where is EPO produced in early embryonic/foetal life
expressed in the yolk sac
Where is EPO produced in the adult?
The Kidney
Describe the regulation of Erythrocyte production
Reduced transport of O2 > Renal secretion of erythropoietin > Increased Production of erythrocytes in the bone marrow > Increase in circulating Erythrocytes > Restoration of the O2 transport
Describe what happens to RBCs as they age
- Lose sialic acid residues from their surface, this exposes galactose moieties that induce their phagocytosis
- Become more fragile
- May become swollen due to failure of normal membrane function
Describe the process of Erythrocyte breakdown
- Damaged RBCs phagocytosed by Macrophage
- Recycling of Haemoglobin
- Iron reused for RBC production in bone marrow
- In liver Iron is stored as ferratin, bilirubin excreted in bile
What is transferrin?
protein that transports iron through circulation
What is ferratin?
Primary intracellular iron-storage protein keeping iron in a soluble and non-toxic form
What is haemosiderin?
- orange brown pigment
- accumulation of iron released form haeme molecules loosely complexed with protein
What would removal of the spleen do to the lifespan of erythrocytes
Lifespan increase - this is due to the spleen having narrow passages, which increases the likelihood of erythrocyte rupture when they pass through the spleen
