Erythropoiesis is the process where erythrocytes (red blood cells) are produced. In fetal development, erythropoiesis occurs first in the yolk sac, then the liver, and finally the bone marrow. In adults, erythropoiesis exclusively occurs in the red bone marrow. The process begins with hematopoietic stem cells differentiating into committed erythroid progenitor cells. These cells undergo a series of changes as they mature, reducing in size, losing organelles, producing hemoglobin, and eventually extruding their nuclei to form reticulocytes and then mature erythrocytes over the course of about 7 days.

1. Erythropoiesis
Dr maria idrees; PT
Dpt; TUF
MS NMPT; RIPHA

2. Erythropoiesis is the process of the origin,
development and maturation of erythrocytes
Hemopoiesis or hematopoiesis is the process of
origin, development and maturation of all the blood
cells

3. Site of erythropoiesis
In fetal life
Occurs in three stages
1. Mesoblastic stage
During first two months of intrauterine life RBCs produced
from mesenchyme of yolk sac
2. Hepatic stage
From third month of intrauterine life liver is the main organ
that producesRBCs. Spleen and lymphoid organs also
involved.
3. Myeloid stage
Last three months RBCs produced from bone marrow and
liver

4. In new born babies,
children and adults
RBCs are produced only from the red bone marrow.
Upto age of 20 years, produced from red bone
marrow of all bones
After the age of 20 years, produced from
membranous bones
In adults liver and spleen may produce the blood cells
if bone marrow is destroyed

5. Process of erythropoiesis
Stem cells
Stem cells are the primary cells capable of self
renewal and differentiating into specialized cells.
Hemopoietic stem cells in the bone marrow are called
uncommitted pluripotent hemopoietic stem cells
(PHSC).
PHSC IS DEFINED as the cell that can give rise to all
types of blood cells.
But the best source of these cells is the umbilical cord
blood.

6. • When the cells are designed to form a particular
type of blood cell, the uncommitted PHSCs are
called committed PHSCs. Committed PHSC is
defined as a cell, which is restricted to give rise to
one group of blood cells.

8. CHANGES DURING ERYTHROPOIESIS
• Cells of CFU-E (Colony Forming Unit-Erythroid)pass through
different stages and finally become the matured
RBCs. During these stages four important changes
are noticed.
1. Reduction in size of the cell (from the diameter of
25 to 7.2 µ)
2. Disappearance of nucleoli and nucleus
3. Appearance of hemoglobin
4. Change in the staining properties of the
cytoplasm.

9. STAGES OF ERYTHROPOIESIS
• Various stages between CFU-E cells and matured
RBCs are:
1. Proerythroblast
2. Early normoblast
3. Intermediate normoblast.
4. Late normoblast
5. Reticulocyte
6. Matured erythrocyte.

13. 1. Proerythroblast
(megaloblast)
First cell derived from CFU-E
Large in size
Large nucleus
Nucleus has two or more nucleoli
Does not contain hemoglobin
Multiplies several times and finally formes cell of next
stage called early monoblast
Synthesis of hemoglobin starts

14. 2. Early normoblast
Little smaller than proerythroblast
Nucleoli disappears
Condensation of chromatin network
Also called basophilic erythroblast

15. 3. Intermediate normoblast
Cell is smaller than early normoblast
Nucleus still present
Hemoglobin starts appearing
Also called polychromophilic or polychromatic
erythroblast

16. 4. Late normoblast
Diameter of cell decreases further
Nucleus becomes very small
Quantity of hemoglobin increases
Before it passes to the next stage, nucleus disappears
called pyknosis

17. 5. Reticulocyte
Known as immature RBC
Slightly larger than matured RBC
During this stage, cell enters the blood capillaries

18. 6. Matured erythrocytes
Reticular network disappears and cell becomes
matured RBC
Biconcave shape
With hemoglobin but without nucleus
It requires 7 days for development and maturation of
RBC from proerythroblast
Requires 5 days upto the stage of reticulocyte
Reticulocyte takes 2 days to become matured RBC