L2 Structure of RBCs and Erythropoiesis Flashcards
what are erythrocytes?
they are non-nucleated cells that contain globular protein hemoglobin and are responsible for the transport of oxygen from the lungs to the tissue and carbon dioxide and protons from tissues back to the lungs.people living at high altitudes have a larger number of erythrocytes. they have an average life span of 120 days. when its time for degradation for the erythrocyte it is marked with oligosaccharides on the surface and they are destroyed by the macrophages of spleen bone marrow and liver.
what are the structural adaptations of RBCs?
1) Shape: biconcave disc like shape which provides a larger surface are relative to its volume, enhancing its capability for gaseous exchange
2) during erythrocytes development in the bone marrow, it expels all its organelles and nucleus to provide more space for hemoglobin
3) RBCs are packed with hemoglobin which is concentrated at the periphery of the cell to facilitate gaseous exchange.
what’s different about the cell membrane of erythrocytes?
its molecular structure provides it with high degree of flexibility, thus can tolerate shearing forces, while squeezing through tiny blood capillaries while maintaining structural and functional integrity.
transmembrane proteins of RBCs?
Glycophrin A (MNS blood groups) RH factor
Ion channels
it has calcium dependent potassium Chanels and sodium-potassium adenosine triphosphatase which transport Cl and HCO3
Network of cytoskeleton?
spectrin adducin and ankyrin
the network of cytoskeleton is attached to the cytoplasmic aspect of the cell through anchoring peripheral proteins—> ankyrin. this network helps maintain the biconcave disc like shape of the cell.
Name the condition due to synthesis of abnormal spectrin
Hereditary spherocytisis which is characterized by fragile RBCs, transport less oxygen and the are more likely to be broken down by the spleen causing Anemia
how are blood groups determined
the extracellular surface of the RBCs has specificities inherited carbohydrate chains that act as antigen and determine the blood type
Haemopoiesis
post natal hemopoiesis occurs in the bone marrow. Daily 10^11 blood cells are produced in the bone marrow to replace dead destroyed and lost blood cells. during hemopoiesis stem cells go through many divisions and differentiate through several intermediate stages, eventually giving rise to mature.
where dopes all blood cells arise from? and what’s its percentage relative to the nucleated cells in the bone marrow
PLURIPOTENT HEAMOPOIETIC STEM CELLS and they account for 0.1% of nucleated cells in the bone marrow.
PHSC are amitotic but can undergo bursts of cell division giving rise to?
more PHCS and 2 types of multipotential heamtopoietic stem cells
1) colony forming unit lymphocyte (CFU-LY)
2) colony forming unit granulocyte erythrocyte monocyte and megakaryocyte.
these 2 types are responsible for forming multiple progenitor cells.
Erythropoiesis?
its the formation fo RBCs under the effect of several cytokines, which are interleukin-3 interleukin-9 erythropoietin hormone and granulocyte macrophage colony stimulating factor (GM-CSF)
when does HB synthesis start?
in the polychromatophilic erythroblasts
what is the progenitor cell for RBCs
its the colony forming unit erythrocytes CFU-E
what is the first precursor cell?
proerythroblast
