RBCs are biconcave disks that are 62.5% water, 35% hemoglobin, and 2.5% other substances. Their membrane is composed of a lipid bilayer and integral proteins like band-3 and glycophorins. The membrane skeleton, made of spectrin and ankyrin, maintains the biconcave shape and anchors the lipid bilayer. RBCs primarily use glucose through the Embden-Meyerhoff pathway to generate ATP for metabolism. Erythropoiesis occurs in three stages - the mesoblastic, hepatic, and medullary stages - and is regulated by factors like erythropoietin and nutrients.

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.

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.

9. Steps of Erythropoiesis

10. 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.

11. Thank you