3. HEMATOPOIESIS
• Mature blood cells have a relatively short life
span
• Must be continusly replaced by stem cells
• Stem cells produce in HEMATOPOIETIC ORGAN
4. HEMATOPOIESIS
ERYTHROPOESIS: Formation of the
erythrocytes (RBCs red blood cells)
LEUKOPOESIS: Formation of the white blood
cells
GRANULOPOESIS:Formation of the
granulocytes (neuthrophil, eosinophil, and
basophil
THROMBOPOESIS: Formation of the platelets
5. Hematopoesis loation
Hematopoesis occour in primary and secondary
organs:
primary organs include:Bone marrow and
thymus
secondary organs include:spleen,lymphatic
system and tonsils
THYMUS: Glandular lymphatic organ near the
heart where T lymphocytes mature well
developed at birth and increase in size until
puberty when it starts to decrease in size.
6. PRENATAL HEMOPOIESIS
• Subdivide into four phases :
– Mesoblastic :
• begin after 2 weeks after conception at yolk sac
• Mesenchymal cells aggregate into blood islands
– Hepatic
• Begins at 6 weeks until end of gestation
• Nucleated erythrocyte
• Appear of leucocyte (8th week)
– Splenic
• Begin at second trimester until end of gestation
– Myeloid
• Begin at the end of second trimester
• Hemopoiesis at bone marrow
7. POSTNATAL HEMOPOIESIS
• Hemopoiesis almost exclusively in BONE
MARROW
• Stem cells undergo
– multiple cells divisions
– and differentiation
• Replace the cells that leave the blood stream,
die or destroy
8. Haematopoiesis during foetal life and infancy
Blood cell production begins at 14–20 days in the foetal sac and this is the site
of haematopoiesis for about 2 months. The liver and spleen become the main
sites of blood cell production during the second trimester of pregnancy and
foetal bone marrow in the third trimester. At birth, haematopoiesis is
confined to the bone marrow. During infancy and up to about 4 years of age,
almost all the bones of the body contain blood cell producing red marrow.
Haematopoiesis during adult life
By about 25 years of age, the main sites of haematopoiesis are the vertebrae,
ribs, sternum, skull bones, pelvis and sacrum, and the proximal ends of the
femur and humerus. At these sites about half the marrow is red active cell
producing marrow and the remainder, non-cell producing yellow fatty
marrow. Other bone marrow cavities in the body contain nonhaematopoietic
fatty marrow. In certain blood disorders, e.g. chronic dyserythropoietic and
haemolytic anaemias and myelofibrosis, blood cell production can resume in
the liver and spleen (extramedullary haematopoiesis) and the fatty marrow in
some bones can become replaced by haematopoietic marrow.
9. HEMOPOIETIC GROWTH FACTORS
Table 10-6 Gartner colour text histology
• Regulated the hemopoiesis
• Produce by spesific cells
• Acts on spesific stem cells, progenitor cells, and
precursor cells
• The route to deliver growth factor :
– Via blood stream
– Secrete near the hemopoietic cells
– Direct cell-cell contact
• Induced rapid mitosis or and differentiation
• Most ot them are glycoproteins
