Hematopoiesis

• The central part of the white pulp part of the spleen is called the germinal center
• The germinal center of the white pulp contains macrophages, lymphocytes and dendritic cells
• The red pulp of the spleen acts as a filter with its cord of Billroth removing glucose from cells that lead to their removal
• The selective phagocytization of a cell by the spleen and degrades their organelles is called culling
• Pitting means the intracellular removal of damaged inclusions or damaged surface membrane of an rbc
• The marginal zone of the spleen is a meshwork that consists of specialized b cells, macrophages and blood vessels
• The extramedullary hematopoiesis, is the counter part of hepatic phase, in adult
• Mesoblastic phase of hematopoiesis begins at 19th day of gestation
• The mesoblastic phase of hematopoiesis occurs intravascularly
• The phase of hematopoiesis that does not contribute to the definitive hematopoiesis is the mesoblastic phase
• The hepatic phase of hematopoiesis begins at 4th-5th weeks of gestation
• The liver continues to be a hematopoietic source until 1-2 weeks after birth
• The hepatic phase is the phase of hematopoiesis wherein the lymphoid cells begin to appear
• In the medullary phase of hematopoiesis the M:E ratio is already at 3:1
• 3 weeks after birth, the bone marrow becomes the only active source of hematopoietic cells until 5-7 year old
• In the red marrow, the normoblasts are found surrounding the iron-laden macrophages
• In the red marrow, the normoblasts are found outside the surfaces of vascular sinuses
• In the red marrow, the megakaryocytes are found near the vascular walls of sinuses
• In the red marrow, the immature granulocytes are found inside the cords
• Retrogression is the process of red marrow replacement by the yellow marrow
• There is equal amount of red marrow and yellow marrow in adults (or 60% red marrow and 40% yellow marrow)
• The monophyletic stem cells theory suggests that all blood cells are derived from a single pluripotent stem cell
• The polyphyletic stem cell theory suggests that each cell blood lineage is derived from its own unique stem cell
• The common lymphoid progenitor cells give rise to B cells, T cells and NK cells
• Stem cells exist in a ratio of 1:1000 nucleated blood cells
• Mitotic index is the calculated number of cells undergoing mitosis which is normally around 1-2%
• Mitotic index indicates increased in proliferation except in Megaloblastic anemia wherein there is prolonged mitosis
• G1 takes about 10 hours
• S phase wherein DNA are synthesized takes about 9 hours
• The G2 takes about 4 hours
• The M phase or mitosis phase takes about 1 hour
• The interphase correlates the G1, S and G2 phase
• The phase wherein t he chromosomes condense is the prophase
• The phase wherein the centrosomes move to the opposite of the pole is the prometaphase
• The phase wherein the sister chromosomes separate is the anaphase
• The phase wherein the chromatids move to the opposite pole and cell divides is the telophase
• The rest stage or quiescence or repair stage of mitosis is the G0 phase
• Cytokines are glycoproteins that regulate the maturation, proliferation and differentiation of hematopoietic cells
• Interleukins that are positive influences include IL-1, 3, 6, 9, 11, GM-CSF and kit-ligand
• Negative influence cytokines include Transforming growth factor B, TNF-a and interferons