Presentation notes of Blood Stem
Cells origin in Bone Marrow, Functions & Lifespan in word/ .pdf/.ppt
STEM CELLS
The stem cells are the primitive cells
in the bone marrow, which give rise to the blood cells. As the stem cells can
give rise to different types of blood cells, these are called pluripotent
hemopoietic stem cells (PHSC) .
In the earlier stages, the stem cells
are not designed to form a particular type of blood cell. And it is also not
possible to determine the blood cell to be developed from these stem cells. So
at this stage, the cells are called uncommitted pluripotent hemopoietic stem
cells (Uncommitted PHSC).
When the cells are designed to form a
particular type of blood cell, the stem cells are called committed pluripotent
hemopoietic stem cells (Committed PHSC). The committed stem cells are of two
types namely:
1.
Lymphoid stem cells (LSC) which give rise to lymphocytes.
2.
Colony forming blastocytes, which give rise to the blood cells other
than lymphocytes. When grown in cultures, these cells form colonies hence the
name colony forming blastocytes. There are different units of colony forming
cells as follows:
- Colony
Forming Unit—Erythrocytes (CFU-E).
The stem cells of this unit develop into erythrocytes.
- Colony
Forming Unit—Granulocytes/Monocytes (CFU-GM).
These cells give rise to granulocytes (neutrophils, basophils and
eosinophils) or Mono-cytes.
- Colony
Forming Unit—Megakaryocytes (CFU-M).
From these, platelets are developed.
CHANGES DURING ERYTHROPOIESIS
The stem cells of the colony forming
unit—E (CFU-E) pass through different stages and finally become the matured red
blood cells. During this process four important changes are noticed.
1.
Reduction in size of the cell (from the diameter of 25 m to 7.2 m)
2.
Disappearance of nucleoli and nucleus
3.
Appearance of hemoglobin and
