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Flashcards in Histo Deck (9)
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What is bone marrow?

spongy tissue in the middle (medullary) cavities of bone

red marrow - active bone marrow, full of dividing stem cells and precursors  precursors of mature blood cells, in adults, only some bones are used for this

yellow marrow - inactive bone marrow - dominated by fat cells - may be reactivated (extreme blood loss)


adults 50 red : 50 yellow


How does one examine bone marrow?

  • bone marrow biopsy (large bore needle - captures bone architecture)
  • fine needle aspirate 
  • typically get both 


Describe general features of bone marrow biopsy?

few things to highlight:

  • bony trabeculae around
  • reticular fibers are spider web that support all the cells = meshwork (remember black spider webs from before - not stained here) = fibroblasts
  • meshwork of vascular sinuses (purple dots) - blood cells leave marrow via sinuses (S) - light red dots
  • haemopoietic cells ( red, H)
  • adipocytes (A)
  • about 50% A and 50 H (remember its 50 % red marrow and 50% yelllow marrow in adults )
  • large dot on the bottom is megakaryocyte that will produce platelets


What does bone marrow smear look like?

picture attached

RBC like cells are in bone marrow, since this is bone marrow aspirate, these are still immature RBCs - reticulocyte


Which cells come from lymphoid lineage?

hemopoietic stem cell -> common lymphoid progenitor or common myeloid progenitor


in common lymphoid progenitor:

  • NK cell
  • T cells
  • B cells -> plasma cells


Which cells come from myeloid lineage?

hemopoietic stem cell -> common lymphoid progenitor or common myeloid progenitor 


common myeloid progenitor ->  granulocyte / monocyte progenitor:

  • dendritic cell
  • neutrophil
  • basophil
  • mast cell
  • eosinophil
  • monocyte -> macrophage

common myeloid progenitor -> megakaryocyte/erythrocyte progenitor:

  • magakaryocyte -> platelet
  • reticulocyte -> erythrocyte (extrusion of nucleus and organelles - reduces in size; goal is to make as much Hb as possible before maturity -> does this by having a lot of ribosomes, etc - > early RBCs stain extremely basophilic - full of proteins! and as cells mature, these ribosomes and other synthesizing parts disappear and cells become eosinophilic)




Describe stages in RBC lineage?

  • PROerythroblast (pale-purlle nucleus, very little and very dark cytoplasm)
  • BASOPHILIC erythroblast: intensely basophilic b/c ribosomes need to synthesize Hb, ribosomes are made of rRNA and RNA stains basophilic
  • POLYCHROMATIC erythroblast (change in colour, both basophilic (some ribosomes remaining) and eosinophilic (b/c Hb is eosinophilic)), greyish cytoplasm
  • NORMOBLAST: more eosinophilic cytoplasm b/c high HB content. very small and dark nucleus (basophilic)
  • RETICULOCYTE: no more nucleus, but still could have some purple dots - has some rRNA remaining (if in bone marrow always reticulocyte b/c not yet matured), if in blood, could be reticulocyte or erythrocyte


RBC development timelines?

  • 5-7 days for full cycle form proerythroblast to RBC
  • reticulocyte takes 2-3 days in blood to mature to RBC (so at least 1% of all RBCs are normally reticulocytes)
  • normal lifespan about 120 days
  • 1 proerythroblast ~ 32 mature erythroblasts because of mitosis in early stages of maturation (proerythroblast to polychromatic erythroblast ; remember this as normoblast is still "normal" b/c has nucleus but it is condensed and tiny, so no longer reproducing)


What is left shift?

Left shift or blood shift is an increase in the number of immature leukocytes in the peripheral blood, particularly neutrophil band cells.

Neutrophil band cell = cell that passed metamyelocyte stage, but is not yet mature neutrophil (hematopoietic stem cell -> common myeloid progenitor -> myelocyte (granulocyte already) -> metamyelocyte (granulocyte with indented nucleus, like horse-shoe, more mature)