OVERVIEW OF STEM CELL (HAEMOCYTOBLAST) IN HAEMATOPOIESIS

 HAEMATOPOIESIS- Formation of blood cells.

Location-Bone marrow (centre part of the bone when you take a cross section)
Hepatopoitic stem cells -----Progenitor cells(myeloid and lymphoid)-------Precaurser cells (Blast suffix) like  proerythroblast ,myeloblast.monoblast,lymhoblast and megakaryoblast -------Formed elements(RBC,WBC.Platelets).

Platelets or thrombocytes are the progenetors of megakaryocytes.
Granulocytes are precursors are myeloblast(unipotent ) .
Monocyte -Precursor is monoblast (which is found in bone marrow .They mature into monocytes which in turn develop into macrophages .


Primitive hematopoietic stem cells are progenitors for the primitive hematopoietic cells of the Yolk Sac that serve as the source for primitive erythrocytes, megakarocytes and macrophages. These progenitors are committed to a single lineage and appear first in 5th month development.Hematopoiesis originates in the early yolk sac but as embryogenesis proceeds this function is taken over by the fetal liver and spleen, then later by the bone marrow where it continues throughout life.
                                             Image source credit -https://www.wikipremed.com/image.php?                                                                     img=040706_68zzzz373750_Illu_blood_cell_lineage_68.jpg&image_id=373750
MCQs.
1.In adults haematopoiesis mainly
occurs in which of the fol¬lowing
A. Long bones B. Liver
C. Spleen D. Flat bones                                            Ans.D
2.During foetal life, haematopoiesis commences in the bone marrow by: 
A. 2nd to 3rd month 
B. 4th to 5th month 
C. 6th to 7th month
D. 7th to 8th monthAns. B
3.Where does haematopoiesis take place?

a) Lungs

b) Pancreas

c) Liver

d) Bone marrow.

Ans. d

4.Which of the following is the earliest site of hematopoiesis in the embryo:

 A  Bone marrow
 B  Liver
 C  Spleen
 D  Yolk sac

Ans.D

5.Megakaryocytes give rise to-

a.RBC

b.WBC

c.Thrombocytes(Platelets)

d. None of the above

Ans. c

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