26: Hematopoiesis - Steele Flashcards
hematopoiesis =
formation of blood cells
functions of hematopoiesis
- provides the cellular elements of the peripheral blood; takes place in the bone marrow
- delivery of oxygen to the tissues + providing host cell defense
- replaces of 0.5 x 10to12 cells/day
what is a normal hematocrit level?
45-50%
with blood doping and rhEPO it could go up to 80%
life spans: lymphocytes RBC platelets granulocytes macrophages
years 120 d 7-10 d 6-8 hrs months - years
eosinophls
neutrophils
basophils
are….
granulocytes
a smear of the bone marrow would contain mostly…
granulocyte precursors
give rise to progenitor cells of all lineages
hematopietic stem cells
self renewal AND differentiation
0.1-0.01% of bone marrow cells; highly proliferative
purpose bone marrow stromal cells
maintenance and differentiation of hematopoietic cells
ex: adipocytes, fibroblastoid cells and reticuloendothelial cells
more primitive/earlier in differentiation. more ______ bind to stromal cells
tightly/firmly
stem cells/ primitive precursors bind firmly; maturing precursor cells nonadherent
G-CSF granulocyte colony stimulating factor –>
released by macrophages at inflammatory sites –> circulates to bone marrow –> production/release of NEUTROPHILS
EPO erythropoietin —>
produced/released by peritubular interstitial cells (kidney) in repsonse to hypoxia –> circulates to bone marrow –> production and release of RBC
increased oxygen pressure inhibits production of EPO
TGFbeta transforming growth factor beta –>
downregulation of stem cell growth/differentiation by TGFbeta by decreasing cell surface receptors for growth/differentiation cytokines
why would you give someone G-CSF?
ex: pt on chemo, need to increase neutrophils,
ex: bone marrow transplantation (some of bone stem cells get into peripheral blood with G-CSF, harvest stem cells from blood)
GM-CSF can do some of the same things but worse side effects
why would you give EPO?
anemia as result of renal insufficiency –> increase RBC mass
yellow v. red marrow
yellow is inactive and mainly adipose tissue
red- active in hematopoiesis
young all is red, by 18 red only in ribs, sternum and pelvis
what is extramedullary hematopoiesis?
takes place in spleen and liver when bone marrow dysfunctional or unable to meet the demands on it
hematopoiesis but not in the bone marrow
as a cell matures.. cell size \_\_\_\_ n:c ratio \_\_\_\_\_\_ nucleoli \_\_\_\_\_\_\_ cytoplasmic staining \_\_\_\_\_
decreases
decreases
decrease in number to zero
darker blue to lighter blue because decreasing RNA
describe a RBC
smaller cell size
lower N:C ratio
no nucleoli
lighter cytoplasm
reticulocytes and erythrocytes do not have any nucleus
the formation or production of RBC
erythropoiesis
maturation sequence of RBC
stem cells –> rubriblast –> prorubricyte –> rubricyte –> metarubricyte –> reticulocyte –> mature erythrocyte
production of cells in the granulocytic lineage, including neutrophils, eosinophils and basophils
granulopoiesis
sequence of development for granulopoiesis
stem cell –> myeloblast –> promyelocyte –> myelocyte –> metamyelocyte –> band –> granulocyte
what is a band cell?
almost but not quite mature granulocyte
“shift to the left”
shifting back to less mature forms
% of band forms in the blood
bone marrow is releasing cells as immature band cells because trying to keep up with infection for example
circulation v. marginating pools of neutrophils
about half neutrophils are zooming around in blood, about half bound to the walls of blood vessels
________ remove dead granulocytes from circulation
splenic macrophages
histiocytes
kupffer cells
osteoclasts
microglial cells
loose connective tissues
liver
bone
nervous system
all different names for macrophages
“baby macrophages”
monocytes
stem cell –> monoblast –> promonocyte –> monocyte –> macrophage
production of cells in lymphocytic lineage, including T lymphocytes, B lymphocytes or natural killer NK cells
lymphopoiesis
stem cell –> lymphoblast –> prolymphocyte –> lymphocyte
develop entirely in bone marrow and are released into the peripheral blood
only the B lymphocytes and NK cells
activated b cells give rise to …
plasma cells and memory cells
t cells are in the bone marrow until prothymocytes are released into peripheral blood to migrate to the …
thymus
once in thymus termed thymocytes and then differentiate into t lymphocyte subsets
most die in thymus (positive and neg selection)
once leave thymus, populate lymphatic organs
production of platelets
thrombopoiesis
anuclear cytoplasmic remnants of megakaryocytes
thrombocytes
role in hemostasis –> limit bleeding, repair endothelium
which of the lymphocytes are part of innate immuity?
NK cells
thrombopoiesis is stimulated by…
thrombopoietin
- promotes megakaryocyte precursor production
- stimualtes endomitosis (mitosis without cytoplasmic divisions)
each megakaryocyte can become 100-1000 platelets
maturation sequence for thrombopoiesis
stem cell –> megakaryoblast –> promegakaryocyte –> megakaryocyte –> platelet
where is an emergency reserve of platelets found?
spleen
platelets are phagocytized in liver or spleen
quantity of each cell type per unit volume
absolute cell count
differential count is a relative count that gives the % of each cell type
absolute cell count for a cell type =
total WBC count X % cell type
most bone marrow is…
granulocytes 50-70%
only 2% are RBC precursors
stem cells are the least %
0.5 - 1.5% of RBC
reticulocytes aka slightly immature red blood cells
shift to left if body is being stressed to make more RBC and sends them out immaturely
