Erythropoiesis Flashcards
Outline blood composition
Extracellular fluid & cells
-Fluid (plasma)
92% water
7% protein
1% other
-Cells
Erythrocytes (90%)
Leucocytes
neutrophils
basophils
eosinophils
T lymphocytes
B lymphocytes
NK cells
monocytes
Thrombocytes (platelets)
Outline the composition of Erythrocytes
Haemoglobin represents 95% of erythrocyte protein
(1) Globin
two pairs of polypeptides:
x2 alpha & x2 beta (or gamma, delta or epsilon)
(2) central haem group containing an iron atom that can bind a molecule of O2
Describe the structure and erythrocytes
Around 7 micrometers in diameter
Typical lipid bilayer membrane of globular proteins
- Biconcave disc shape which increases surface area (20-30%)
- Elasticity/deformability so they are able to pass through capillary diameters as small as 3-4μ
Failure of Na+ ion movement across erythrocyte cell membranes leads to swelling and loss of the normal biconcave disc morphology.
Outline typical erythrocyte properties in a dog
Uniform size
Central pallor (concave)
Outline typical erythrocyte properties in a cat
Smaller erythrocytes
Anisocytosis (variation in size)
Scarce central pallow (less concave)
Outline typical erythrocyte properties in a horse
Rouleaux formation (clustering of RBC in standing blood)
Outline typical erythrocyte properties in a ruminant
Crenation (spiky appearance)
Variation in size
Outline typical erythrocyte properties in a camelid
Ellipsoid
Outline typical erythrocyte properties in a the avian and reptile species
Nucleated
Larger
Early stages are rounded and may be binucleate
Occasional cells lose their nucleus and are termed erythroplastids.
Explain how the structure of erythrocytes relates to function
-Erythrocytes are metabolically active.
This is because energy is required to maintain electrolyte gradients across the plasma membrane and of haemoglobin molecules.
-There are no organelles
As there is no mitochondria, energy is derived by anaerobic metabolism of glucose, which is important as it allows avoidance of consumption of any oxygen they are carrying
-No nucleus in mammalian erythrocytes so division is by stem cells, this is because it creates an increased space for haemoglobin and allows biconcave shape
Outline the main role of erythrocytes
Haemoglobin allows for the transport of O2 from lungs to the cells , and also, to an extent, the transport of CO2 from cells to the lungs
CO2 dissolved in plasma (70%) and 30% in the haemoglobin.
Achieved because the reaction of CO2 with water to form carbonic acid by use of enzymes carbonic acid anhydrase. This causes release of hydrogen molecules which affect pH of the blood creating hydrogen carbonate which is dissolved in plasma to be transported to the lungs
Describe the binding of O2 and CO2 to haem groups
In regions of high oxygen concentration (e.g. in the lung):
Globin releases CO2 and iron binds to O2 (oxyhaemoglobin)
In areas of low oxygen concentrations:
O2 is released and CO2 bound (carbaminohaemoglobin)
How is erythrocyte binding and release affected in hypoxic tissues
In hypoxic tissues (lack of O2) a carbohydrate (2,3-diphosphoglyceride) is released and that facilitates release of O2 from erythrocytes.
Explain the role of haemoglobin of vasodilation
Haemoglobin also binds nitric oxide – a neurotransmitter that causes dilation of blood vessels. By doing this it permits maximal tissue perfusion for supply of oxygen/removal of waste products.
Explain the binding of CO to Haem groups
Carbon monoxide has greater affinity for haem than oxygen; carbon monoxyhemoglobin can lead to a ‘healthy?’ cherry red colour of mucous membranes.