2. STRUCTURE OF RBCs
62.5% water, 35% hemoglobin & 2.5% other substances (glucose, lipids).
Circular, biconcave in shape.(explained)
Red cell membrane is made up of integral protein, lipid bilayer and membrane
skeleton.
Lipid bilayer:- Provide impermeable barrier.
Maintain a slippery exterior, so that red cells do not stick to
the vascular endothelium.
Integral protein:- important membrane proteins are band-3 protein, glycophorins,
Rh D protein and various ion channels.
3. Integral proteins
Antigenic determination and cellular metabolism.
Band-3 is the major anion exchanger (chloride-bicarbonate exchange) and also
regulates metabolic pathways.
Glycophorins modulate interaction between red cells and interaction of red cells
to endothelium.
Glycophorins-C provides stability and shape to red cell membrane and its
deficiency leads to elliptocytosis.
4. Membrane skeleton
Present on internal side of red cell membrane.
Ankyrin and Spectrin are important membrane skeleton proteins.
Spectrin is composed of 2 subunits: α and β. these subunits align in antiparallel
fashion to form flexible rod like structure.
Spectrin molecules maintain cellular shape, provide structural support to
membrane lipid bilayer and regulate lateral mobility of integral membrane
proteins.
Ankyrin provides primary linkage between membrane skeleton and lipid bilayer.
5.
6. Metabolism of red cells
Glucose is the primary fuel for red cells. ATP is formed by Embden-Mayerhoff
pathway. The HMP shunt provides NADPH.
90% of glucose is oxidized by EM pathway and 10% by HMP shunt.
2 ATP molecules are generated by glycolysis through EM pathway.
HMP shunt generates NADPH, keeps glutathione in reduced state, which is a
strong reducing agent and prevents damage to the red cell
7. Functions of RBCs
Transportation of gases.
Blood group classification.
Maintenance of acid base balance.
Contribute to 50% of viscosity of blood.
8. ERYTHROPOIESIS
Process of formation of red cells.
Three stages of erythropoiesis:- mesoblastic, hepatic and medullary.
Mesoblastic Stage: during intrauterine life, erythropoiesis first takes place in
mesoderm of yolk sac.
Hepatic stage: from the 5th week of gestation, erythropoiesis takes place in the
liver and spleen.
Medullary stage: from the 5th month of intrauterine life, the bone marrow starts
forming red cells.
After birth, bone marrow becomes the sole site of erythropoiesis.
