blood: haematopoiesis Flashcards
concentration of RBC, platelets and WBC
RBC: 4-6 x 10^6/ microlitre
Platelets: 1.5-4 x 10^5/ microlitre
WBC: 4-11 x 10^3/ microlitre
when and how does haematopoiesis begin in utero
2-2.5 weeks in utero
mesenchyme cells-> endothelial cells arranged in a ring so blood island forms in lumen-> endothelial cells become blood vessel; blood islands become blood cells
totipotent vs pluripotent vs multipotent vs unipotent vs haematopoietic stem cell
totipotent: zygote
pluripotent: differentiates into ectoderm/endoderm/mesoderm
multipotent: multiple but restricted cell types
unipotent: single lineage
haematopoietic stem cell: all blood cells
stages of haematopoiesis
self-renewal-> committed cells-> developmental pathway-> differentiated functional cells
what do lymphoid stem cells give rise to
lymphoid stem cell-> B lymphoblast/Tlymphoblast-> Blymphocyte/Tlymphocyte;
Blymphocyte-> plasma cell
what do myeloid stem cells give rise to
myeloid stem cell-> megakaryoblast-> platelets
myeloid stem cell-> pronormoblast-> reticulocyte-> rbc
myeloid stem cell-> myeloblast-> basophil/eosinophil/neutrophil
myeloid stem cell-> monoblast-> monocyte (in circulation)/macrophage(in tissue)
blood supply/drainage of bone marrow
blood supply: nutrient artery (towards middle of medulla)-> ascending/descending medullary artery-> radial artery (radiates away from centre of medulla towards cortex)-> cortical capillary
blood drainage: endosteal capillary-> medullary vascular sinus (from edge of endoosteum towards the middle of medulla)-> central sinus-> emissary vein (away from middle of medulla)
where does haematopoiesis occur in the bone marrow?
in extra vascular spaces between medullary vascular sinus
RBC lifespan, size, penultimate precursor
120 days; 7 micrometres; normoblast
normoblast size, features, what is it released into blood stream as
7-10 micrometres; highly condensed nucleus/has most haemoglobin/few mito and ribosomes; reticulocyte
reticulocyte features; how long does it take to become a rbc?
no nucleus, few organelles and rna; 1-2 days
platelet production; characteristics; function; protein production ability
produced in bone marrow from megakaryocyte, stimulated by thrombopoietin;
anuclear, discoid shape, 2-4 micrometres, lifespan of 8-12 days;
haemostasis, maintenance of bv, innate immunity against invading pathogens;
limited de novo protein synthesis, secretes mediators in alpha granules/dense granules/liposomes
what happens when platelets are activated?
they become retracted and aggregated
megakaryocyte characteristics and how platelets are formed
large cell (50-75 micrometres in diameter);
single large nucleus that is often polyploidy;
progenitor can go through 5 cell cycles w/o mitosis;
vesicles of ER divide cytoplasm into 2-4micrometre packages (platelet demarcation channels)-> vesicles fuse-> platelets ejected
neutrophil leukocyte circulating percentage, half-life in blood, characteristics, response during inflammation/infection, what’s not so good about neutrophils tho
60%; 6.7h
polymorphonuclear, fully differentiated; very limited protein synthesis
very motile and responsive to chemotaxis, first cell type recruited to inflammation site, phagocytotic;
damages healthy tissue in MS, RA, COPD
how do neutrophils move
they follow a chemokine gradient.
uropod anchors cell and provides traction
pseudopods have chemokine receptors, extending and retracting
eosinophil leukocyte circulating percentage, characteristics, function, how long does it stay in circulation & how long does it live in tissues; associated syndromes
1%;
polymorphonuclear;
extra-cellular parasite killing, associated with gut diseases;
hyper-eosinophilic syndromes in allerigies/asthma/rhinitis
4 types of cytotoxic eosinophil secretory products
Major basic protein: cationic, toxic towards helminthic parasites
eosinophil cationic protein: bacteriocidal, promotes mast cell degranulation
eosinophil derived neurotoxin: antiviral activity in respiratory infection
eosinophil peroxidase: peroxidation of halides and h2o2 , bacteriocidal
monocyte characteristics (size/nucleus shape/other features/lifespan in blood)
20 micrometres;
horseshoe shape
highly motile
2 days
macrophage function
defence against micro-organisms
refuse collection: old RBC/tissue debris
antigen presentation to T lymphocytes
cytokine secretion: regulates haemopoiesis
types of lymphocytes and their sizes
small: B & T; T: helper/cytotoxic; 6-9micrometres
large: natural killer/activated B cells in transit to tissues to become plasma cells; 9-15 micrometres
B lymphocyte characteristics
have surface antibody-> antigen response by proliferating and maturing into plasma cells-> secrete same antibody
T helper/cytotoxic lymphocyte characteristics
T helper: express CD4 marker; secrete cytokines that support other lymphocytes
cytotoxic T cells: express CD8 marker; kills virus infected cells
