Erythropoiesis

Dr. Wasif Haq

Introduction• Red blood cells also called as “Erythrocytes”. • R.B.C. required for transportation of respiratory

gases.• Biconcave disc shaped.• Mean diameter 7.5.-7.8 micrometer.• Initially nucleated, later anucleated.• Flexible cell membrane. • Significance?

Count & Levels• Most numerous amongst all blood cell types.• In males: 5,200,000 (+ 300,000) Million cells/cubic

millimeter.• In females: 4,700,000 (+ 300,000) Million

cells/cubic millimeter.• Why the count in males is greater?

Hemoglobin Levels• Maximum concentrating ability of R.B.C.’s for

Hemoglobin is 34 g/dl.• Every deciliter of blood in men carry 16 grams of

Hemoglobin, while in females; 14 grams.• 1 single gram of Hemoglobin is capable of

combining with 1.39 milliliters of Oxygen.

Functions of R.B.C.’s

• Transportation of Oxygen bound with Hemoglobin: 97% Hemoglobin.

• Carbonic anhydrase enzyme: Transportation of CO2 from tissues back to lungs in form of ‘bicarbonate’ ions.

• Acid-base buffering.

R.B.C.’s Production• Also known as “Erythropoiesis” or

“Erythrogenesis”.

Intra-embryonic/ Intra-uterine life

Postnatal life

Intra-Embryonic Life

• Initially: Yolk sac.• Second trimester: Mainly liver along with Spleen

& lymph nodes.• Third trimester and after birth : Only in bone

marrow.

Post-natal Life

• Bone marrow of all the bones till 5 years of life.• Relation between age & R.B.C.’s production?• Vertebrae, sternum, ribs and ilia produce R.B.C.’s

throughout life.

Erythropoiesis• Pluripotent Hematopoetic stem cells in bone marrow

(also called as Hemocytoblast) are source for R.B.C.’s.• Any type of blood cell type can be formed by

Hemocytoblasts.• Certain number of Pluripotent Hematopoetic stem

cells will become committed to form only R.B.C.’s , hence called “Committed stem cells”.

• Commitment occurs before any structural differences observed.

• Growth & differentiation inducers.

Haematopoetic stem cell Proerythroblasts Basophil erythroblasts Polychromatophil erythroblasts

Orthochromatic erythroblasts

Reticulocytes

Erythrocyte

Nutrients Required• Vitamin B12, Folic Acid & Iron.• Deficiency of Vitamin B 12 & Folic Acid-

Maturation failure.• Larger than normal size R.B.C.’s are produced

called Macrocytes.• Macrocytes can carry O2 but are extremely

fragile.• B12 deficiency takes 3-4 years to develop.• Folic acid destroyed by cooking vegetables, meat

& fruits.

Nutrients Required

• Sprue= Small intestinal disease, difficulty in absorbing Folic acid & Vitamin B 12 due to deficiency of Intrinsic factor.

• Iron: Stored in body in form of “Ferritin”. • Hemoglobin: 65% Iron, Myoglobin 4%, Reticulo-

endothelial cells in bone marrow and liver 15-30%.

Erythropoietin• Concentration of R.B.C.’s is not important but

functional ability to transport respiratory gases.• Protein hormone stimulates R.B.C.’s production.• Released from Kidneys (90%) & Liver (10%).• Epinephrine, Nor-epinephrine & Prostaglandins

stimulate Erythropoietin release.• Production starts within minutes, new cells appear

after 4-5 days.• Action: Stimulates Proerythroblast formation from

hematopoietic stem cell and accelerates progression & maturity of cell through different stages of Erythropoiesis.

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