Rbcs function

erythropoesis

1. Structure and Function of RBC. (ERYTHROPOIESIS) Ms. SHAMA PRAVEEN TUTOR PHYSIOLOGY

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. 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

6. Functions of RBCs Transportation of gases. Blood group classification. Maintenance of acid base balance. Contribute to 50% of viscosity of blood.

7. 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 5 th week of gestation, erythropoiesis takes place in the liver and spleen. Medullary stage : from the 5 th month of intrauterine life, the bone marrow starts forming red cells. After birth, bone marrow becomes the sole site of erythropoiesis.

8. Steps of Erythropoiesis

9. Factors affecting Erythropoiesis hormonal factors:- Erythropoietin, androgens, estrogen, thyroxine, interleukins . Dietary factors:- vitamin12, folic acid, iron, proteins, copper, cobalt, vitamin C. Other factors:- intrinsic factors, environmental factors, drugs and chemicals.

10. Thank you