Ertythropoiesis Stages And Regulation

Q. What is erythropoesis and where does it occurs? Give stages of Ertythropoiesis and requirement of each stage.
Answer:

Erythropoiesis:

• Erythropoiesis is the process which involves the origin, development and maturation of erythrocytes.

Erythropoiesis Requirements:

• Oxygen – for regulation of erythropoiesis.
• Nutrients.
  1. Carbohydrates – for energy supply.
  2. Fats for cell membrane.
  3. Proteins for globin formation.
• Minerals.
  1. Iron, manganese, copper, cobalt and nickel help in ‘heme’ formation.
  2. Calcium – increases iron absorption.
     • Vitamins.
     • Vit B12 and folic acid helps in maturation of RBC
     • Hormones.
       1. Erythropoietin – stimulates RBC production
       2. Thyroxine – Accelerate the process.
       3. Sex hormones – androgen stimulates and oestrogen depress the formation of erythropoietin.
       4. Glucocorticoid-stimulates secretion of erythropoietin from kidney.
       5. Growth – hormone – stimulates erythropoietin secretion.
          • Neural-stimulation of the hypothalmus causes an increase in RBC.

Site of erythropoiesis:

Question. Describe the morphology of red blood corpuscles. Briefly outline the stges in erythropoiesis. Mention two factors that affects erythropoiesis.
Answer:

Morphology of red blood corpuscles (RBC):

• RBC is a circular, biconcave, non-nucleated disc.
• Its cell membrane contains circular pores below which lies a contractile layer of lipoprotein – spectrin.
• It maintains the shape and flexibility of RBC membrane and contains antigen.
• RBC has a special type of cytoskeleton which is made up of actin and spectrin.
• Both are anchored to transmembrane protein called ankyrin.

Red Blood Corpuscles Size:

• Diameter -7.2 μ
• Thickness – At the periphery 2.2 μ, At the center – 1 μ.
• Surface area – 120 sqm
• Volume-85-90 cum.

Stages of Erythropoiesis:

1. Proerythroblast.

• It is very large in size occupying almost whole of the cell with diameter 20 μ
• Nucleus is large containing 2-3 nucleoli.
• The cytoplasm is basophilic.
• The proerythroblast multiplies several times to form early normoblast.

2. Early normoblast.

• The cell decreases to diameter of about 15 μ.
• It contains no nucleoli and condensed chromatin.
• It develops into intermediate normoblast.

3. Intermediate normoblast.

• Diameter is of 10 – 12 μ.
• Chromatin is condensed and haemoglobin starts appearing.
• Due to basophilic cytoplasm and acidophilic hemoglobin.
• The cell is called polychromophilic erythroblast.
• It develops into late normbolast.

4. Late normoblast.

• The diameter becomes 8 – 10 μ
• Nucleus is very small with chromatin dot giving cart wheel appearance.
• Cytoplasm becomes acidophilic so the cell is called orthochromic erythroblast.
• Next the nucleus becomes pinpoint called pyknosis.
• It develops into reitculocyte.

5. Reticulocyte Immature RBC.

• It is non-nucleated, basophilic in nature.
• Cytoplasm contains remnants of disintegrated organelles.

6. Matured erythrocyte.

• It is biconcave with diameter of 7.2 μ.
• It contains hemogolobin and is non-nucleated.

Factors effecting erythropoiesis:

1. General factors.

• Erythropoietin.
• Thyroxine.
• Hemopoietic growth factors.
• Vitamins Vit. B, C, D and E.

2. Maturation factors.

• Vitamin B12.
• Intrinsic factor of castel.
• Folic acid.

3. Factors necessary for haemoglobin formation.

• Amino acids
• Iron
• Copper
• Cobalt and nickel.
• Vitamins Vit. C, riboflavin, nicotinic acid and pyridoxine.

Erythropoiesis Regulation

• Factors regulating erythropoiesis are:

1. 1. General factors
      • Erythropoietin
      • Thyroxine
      • Haemopoetic growth factor
      • Vitamins B, C, D & E
   2. Maturation factors
      • Vitamin B₁₂
      • Intrinsic factor of Castel
      • Folic acid
   3. Factors necessary for haemoglobin formation
      • Amino acids
      • Iron
      • Copper
      • Cobalt and nickel
      • Vitamins Vit C, riboflavin, nicotinic acid and pyridoxine

Question. Name two factors that regulate erythropoiesis.
Answer:

1. Erythropoiesis General factors

• Erythropoietin
• Thyroxine
• Haemopoetic growth factor
• Vitamins B, C, D & E

2. Erythropoiesis Maturation factors

• Vitamin B₁₂
• Intrinsic factor of Castel
• Folic acid

3. Erythropoiesis Factors necessary for haemoglobin formation

• Amino acids
• Iron
• Copper
• Cobalt and nickel
• Vitamins Vit C, riboflavin, nicotinic acid and pyridoxine