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Erythropoiesis – Definition, Stimulating Agents & Process

Notes / Presentation  on Erythropoiesis Process & Stages in Human Body for Medical Biology Students in word/ .pdf /. Ppt Format

ERYTHROPOIESIS

DEFINITION

Erythropoiesis is the process by which the origin, develop­ment and maturation of erythrocytes occur. Hemopoiesis is the process which includes origin, development and maturation of all the blood cells.

SITE  OF ERYTHROPOIESIS

IN FETAL LIFE   

During embryonic life, the erythropoiesis occurs in three stages.

  1. Mesoblastic stage: During the first two months of intrauterine life, the primitive red blood cells are produced from mesenchyme of yolk sac.
  2. Hepatic stage: From third month of intrauterine life, liver is the main organ that produces red blood cells. Some erythrocytes are also produced from spleen and lymphoid organs.
  3. Myeloid stage: During the last three months of intra uterine life, the red blood cells are produced red bone marrow and liver.

POSTNATAL LIFE AND IN ADULTS

In newborn babies, growing children and adults, the blood cells are produced only from the red bone marrow.

1.   Up to the age of 5 to 6 years: The red blood cell  produced in red bone marrow of all bones.

2.   From 6th year up to 20th year: The red blood cell produced by red bone marrow of long bones and the membranous (flat) bones.

3.   After the age of 20 years: The red blood cells produced from all membranous bones like vertebra, sternum, ribs, scapula, iliac bones and skull bones and from the ends of long bones. After 20 yea age, the shaft of the long bones becomes yellow bone marrow because of fat deposition and looses the erythropoietic function. During disorders of bone ,the red blood cells are produced in the spleen.

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