Erythropoiesis Flashcards
(28 cards)
What is erythropoiesis
It is the process of production of red cells.
Life span of RBCs
120 days
Normal red cell mass
Males - 26-32 ml/kg of body wt
Females - 23-29 ml/kg of body wt
What are the stages of erythropoiesis
Mesoblastic
Hepatic
Medullary
Mesoblastic erythropoiesis
During IUL erythropoiesis first takes place in the mesoderm of yolk sac and body . During this stage erythropoiesis is intravascular.
Hepatic stage
From the 5th week of gestation erythropoiesis takes place in the liver and spleen.
Medullary stage
From 5th month of IUL the bone marrow starts forming red cells. Erythropoiesis os very slow in 2nd trimester .
Medullary erythropoiesis becomes more effective towards end of the third trimester. After birth bine marrow becomes the sole site of erythropoiesis.
Till adolescence marrow cavity of all bines is involved in erythropoiesis . After which it regresses in the limb bones.
After the age of 20-30 erythropoiesis is mostly limited to sternum , ribs , vertebrae , skull , pelvic and pectoral girdles.
Extramedullary erythropoiesis after birth is abnormal.
What are the 4 major cell stages of erythropoiesis ?
Stem cells
Progenitor cells
Precursor cells
Mature cells
Where are red cells formed from ?
They’re formed from pluripotent hemopoietic stem cells
What are the cellular changes taking place during erythropoiesis ?
Cell size reduces progressively
Size of nucleus and number of nucleoli decreases , chromatin material condenses and finally nucleus disappears.
Staining reactikn of cytoplasm changes from basophilic to polychromatophilic to acidophilic due to the geadual decrease in quantitiy of nucleus
What are pleuripotent stem cells ?
They are the mother stem cells that form the stem cells for different cell lines.
Functions of pleuripotent cells
They have 2 functions -
Self renewal
Differentiation
They constantly renew themselves, thus the bone marrows is never depleted of stem cells.
They also have the capacity to differentiate into different stem cells
Committed stem cells
Formed from pleuripotent cells.
2 series are present myeloid and lymphoid series .
The myeloid series produces the erythroid series ,megakaryoid series , monocytic series and granulocytic series.
The erythroid series gives rise to the progenitor cells.
Types of progenitor cells
BFU-E : burst forming unit - erythroid progenitor cells
CFU-E : colony forming unit - erythroid progenitor cells
Short note on progenitor cells
The BFU-E cells forms large no. of CFU-E cells which then forms a moderate no. of blast cells (erythroblasts)
Precursor cells
Erythroblasts are the first identifiable cells in the bone marrow hence they are the precursors of RBCs .
Erythroblasts are also called normoblasts. Normoblasts arise from pronormoblasts .
Types of normoblasts cells
Early
Intermediate
Late
What are pronormoblasts
They are the firsr identifiable blast cell in the erythroid series. First cells to appear in the bone marrow.
Characteristics of pronormoblast cells
Less cytoplasm (only 20% of cell)
Increased amounts of polyribosomes makes the cell basophilic
Large cell with irregular edges oval in shape (15-20 microm)
RNA content is high — high protein synthesis
Mitosis is present
Hb production hasnt started
Nucleus is large (80% of the cell) contains many nucleoli.
What are early normoblast cells
They are the first appearing erythroblast cells
Features of early normoblast cells
Diameter , 12-18 microns
Cytoplasm is scanty and basophiloc hence they’re also called basophilic erythroblasts .
The nucleus is large (occupies 3/4th of the cell). Contains dark violet stained heterochromatin and pink stained euchromatin . These are linked by linear chains giving the nucleus a wheel spoke appearance.
Hb production starts at this stage
Intermediate normoblast
Formed due to the mitosis of early normoblast.
Characteristics of intermediate normoblasts ?
Smaller in size , radius is 10-15 microns
The cytoplasm changes from blue to pink as Hb content increases and polyribosome content gets diluted.
Nucleus is small and occupies half of the cell. The heterochromatin clumps in the nucleus gives a checkerboard appearance. There are no nucleoli .
The presence of RNA makes the cell eosinophilic .
Hence the cell is polychromatic in nature.
Mitosis activity is reduced
Late normoblast
Produced by last mitosis in the erythropoietic series
