L13- Haematopoiesis Flashcards
What is haematopoiesis
production of RBCS
how many new RBCs are produced per day
4.2 x 10^11 cells
what is the balance that the HMP need
production and destruction of cells
what is HMP stem cell
a multipotent stem cell that can differentiate into different kinds of cells but limited cells only
- through this cell, the body can maintain high production of RBCs
what stem cell can HMP stem cell be further divided into
myeloid and lymphoid stem cell
examples of oligopotent stem cells
erythrocytes, monocyte, T and B cells
how can low freq of HMP stem cells lead to big production of RBCs
-they are self-renewing and proliferative through symmetric (SD) and asymmetric division (ASD)
what cells are produced during the two types of division of HMP stem cells or HSCs
long term and short terms HSCs
- so there is a heterogeneous pool of HCS
difference between LT-HSC and ST-HSC
LT- self renew
ST- limited self renew
what states can LT-HSCs be in
Quiescent and active
in what condition can active LT-HSCs proliferate
- expansion (SD), maintenance (ASD)and differentiation (ASD)
of what expression can HSCs be defined by
surface marker proteins
stages of HMP during emrybonic development
- 0-6 weeks - primitive HMP - produces first few cells
- 2-8 weeks - primitive HSCs move from yolk sac to the AGM
- 2-7 months - HMP becomes definitive and populate liver, thymus, spleen and placenta from AGM
- 7 months + - populate bone marrow and is now important site for HMP
where is HMP found in infants
in all bones
where is HMP found in adults
-ribs, skull, vertebrae, pelvis , strenum
why is the environement important for HCS in HMP and what is this environment
- proper function
- formation of LT-HSCs like during AGM stage
- the environment is bone marrow niche
what is the bone marrow niche
- supports self renewal and differentiation of cells
- has cellular and molecular components
how is quiescent HSC maintained in that state in the bone marrow
receives a signal from immune cells like macrophages
how does Quiescent HSC become active and proliferate
-when LT-HSC becomes associated with osteoclast, the QUI-HSCs lose the signal
what are the functions of substances secreted from other cells in perivascular niche
-drives the proliferation and productions of ST-HSC
what molecular components are there
- ECM - basement membrane, integrins
- physical factors like - elastcity
cells in the blood cell lineages
pluripotent cell -> multipotent progenitors -> commited progenitors -> differentiation of cells
molecules controlling BC differentiation
- cytokines and transcription factors - driving differentiation of cell lineages
- signalling molecules
how does cytokines signalling pathways occur
- the erythropoietin (EPO) or thrombopoietin (TPO) is a signalling molecule that binds to a receptor.
- this initiates cellular pathways and lead to gene transcription
- differentiation of erythro or megaerythro occurs
stages of RBC production
- BFU.CFU erythrocyte
- proerythroblast
- intermediate erythroblast
- late erythroblast
- reticulocyte
- erythrocyte
- HB content increases
stages of platelet production
BFU/CFU megaErthryoctye -megakaroblast megakarocyte -proplatlet forming megakaryocyte -platelets
how is platelets released in a blood vessel
the megaerythrocytes releases proplatelets into the blood vessels and the platelets are released the from the proplatelets
Adaptation of RBCs
flattened biconcave dic
no nucleus
the lifespan of 120 days
transports O2
adapatation of platelets
have granules and cytoskeleton
lifespan of 7 days
haemostasis and release of growth factors for tissue repair
