Blood-erythropoiesis Flashcards
What are the different types of bone marrow?
Red bone marrow:
marrow capable of producing cells
present in babies. By 18 only few sites are left with red bone marrow, they are; proximal ends of long bones, sternum, some flat bones, vertebral bodies, anterior superior iliac spine.
Yellow bone marrow: when fat starts infiltrating the bone marrow.
does not produce blood cells
What are the steps of erythropoiesis?
1) pluripotent haematopoietic stem cell
2) committed stem cell (erythroid & lymphoid series)
3) colony forming units: CFU-E, CFU-mega, CFU-GM
4) proerythroblast
5) early normoblast/ basophil erythroblast
6) intermediate normoblast/ polychromatophil erythroblast
7) late normoblast/ orthochromatic erythroblast
8) reticulocyte
9) erythrocyte
What happens to the committed stem cell (lymphoid series)?
The cells move out of the bone marrow and differentiate to form lymphocytes
Why does the cell size decrease between the first and last cell stage? (Pluripotent stem cell-24 microns, erythrocyte- 7-8 microns)
Cell division and cell maturation occurs simultaneously in the bone marrow. As cell division occurs very rapidly and erythropoiesis occurs in a step wise fashion, the daughter cells have little time to grow to the parent size before it is divided again.
Describe what happens to the nucleus.
Through the subsequent steps, the nucleus:
Decreases in size
Pushed to the periphery- eventually thrown out
OR:
Undergoes pyknosis ( broken down to pieces, finally turns to dust)
Why is the cytoplasm basophilic initially?
It has acidic contents and hence attracts a basic stain.
At the early normoblast stage, why does the cytoplasm attract both basic and acidic stains?
Haemoglobin begins to appear at this stage
Hb is basic in nature- acidophilic
Therefore the cytoplasm attracts both acidic + basic stain
What type of stain does a erythrocyte attract?
Acidophilic( filled with haemoglobin)?
What are the sites of erythropoiesis?
1st trimester- mesoderm if yolk sac (mesoblastic stage)
2nd trimester- foetal liver and spleen (hepatic stage)
3rd trimester- bone marrow of foetal bones begins producing RBCs (myeloid stage)
What are the factors regulating the rate of erythropoiesis?
Tissue oxygenation (hypoxia)
Erythropoietin
Dietary factors- iron, a.a, vitB12 + folic acid
Hormones- testosterone, estrogen, thyroxine
How does hypoxia affect erythropoiesis?
Hypoxia: any condition that decreases the quantity of oxygen transported to the tissues
Hypoxic conditions stimulate erythropoiesis by increasing the activity/ production of erythropoietin
How does high altitude or lead to hypoxia?
Air pressure + O2 pressure is less, therefore less O2 is available for the body
What are the possible causes of hypoxia?
High altitudes
Heart/ lung diseases
Where is erythropoietin synthesised?
90% kidney
10% liver
How does erythropoietin increase rate of erythropoiesis?
Hormone
Hypoxic conditions- interstitial cells if kidney secrete erythropoietin into blood
Reaches the bone marrow- which has specific receptors (Ep-1, Ep-2) on which erythropoietin acts.
By enhancing RBC production until the hypoxia is relieved ( specifically increases conversion of haematopoietic stem cell to proerythroblast. And increases rate of the other steps)
