Erythropoiesis = Development of RBCs
Site: in the red bone marrow.
Steps:
1- Undifferentiated Mesenchymal Cells (UMC):
• 2- Colony Forming Unit (CFU) cells:
• 3- Colony forming unit erythropoietin (CFU-E):
4- Proerythroblasts:
5- Basophilic erythroblasts:
6- Polychromatophilic erythroblasts:
7- Normoblasts:
8- Reticulocytes:
•
9- Mature erythrocyte:
Development of granular leucocytes
(Neutrophils, Eosinophils and Basophils)
Site: in the red bone marrow.
Steps:
1- U.M.C. (see before).
2- C.F.U. (see before).
3- C.F.U. granulocytes(CFUG):
4- Myeloblasts:
• 5- Promyelocytes:
6- Myelocytes:
i. Neutrophil myelocytes: neutrophilic granules.
ii. Eosinophil myelocytes: eosinophilic granules.
iii. Basophil myelocytes: basophilic granules.
7- Metamyelocytes:
•
• N.B.: Neutrophil metamyelocytes are called juvenile neutrophils.
8- Mature granulocytes:
a- Mature eosinophil: with bilobed nucleus.
b- Mature basophil: with irregular nucleus.
c- Mature neutrophil:
- At first, the nucleus becomes curved rod shape (called stab neutrophils).
- Lastly, the nucleus becomes segmented or multilobed (mature neutrophil).
Development of B-lymphocytes
• They develop in the red bone marrow.
• U.M.C differentiate into C.F.U. which differentiate into B-lymphoblasts then B-lymphocytes.
Development of T-lymphocytes
• They are thymus dependent cells.
• UMC (in the bone marrow) differentiate into CFU which migrate to the thymus gland, where they can be changed into T-lymphoblasts then T-lymphocytes.
Development of monocytes
• They develop in the red bone marrow.
• U.M.C. differentiate into C.F.C which differentiate into Monoblasts then Monocytes.
Development of platelets
Site: in the red bone marrow.
Steps:
1- U.M.C.: differentiate into
2- C.F.C.: differentiate into
3- Megakaryoblast:
• Size: It is a large cell.
• Nucleus: indented with clear nucleoli.
• Cytoplasm: basophilic.
4- Promegakaryocyte:
• Size: larger.
• Nucleus: large and lobulated.
• Cytoplasm: basophilic with fine azurophilic granules.
5- Megakaryocyte:
• Size: very large (40 μm).
• Nucleus: large, lobulated and dark stained.
• Cytoplasm: less basophilic and is rich in fine azurophilic granules.
6. Platelet formation:
It is formed by one of the following mechanisms:
i. Numerous invaginations of the cell membrane extend through the cytoplasm dividing the cytoplasm into areas that will be shed as platelets.
ii. Megakaryocytes can extend pseudopodia or platelet ribbons into the blood sinusoids then, the platelets are separated from the tips of these ribbons.
Megakaryocyte Osteoclast
Size: 40 μm 15-30 μm.
Surface: Smooth Ruffled surface
Nucleus: Single and lobulated Multinucleated
Cytoplasm: Basophilic Foamy acidophilic
Site: In the bone marrow In How ships lacunae of bone
Function: Production of platelets Bone destruction
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