hi let's talk about thrombocytes in this video we'll talk about thrombocytes or platelets we'll
discuss how they work and we'll also discuss the cytokine T pout and how it works so platelets art
cells in and of themselves but rather fragments of cells they're derived from cells called mega
carrier blasts now mega carrier blasts come from myeloid stem cells in the bone marrow
that differentiate into colony forming units make area blasts which then further differentiate into
these mega carrier blasts these are impressive cells they're generally about 50 micrometers in
diameter so that's about you know near ten times the size of the average erythrocyte they're also
polyploid they have up to 64 copies of the the chromosomes in them so that's it's quite
an impressive collection of genetic material now what happens is these mega carrier blasts
they make their way down to the sinusoids in the marrow so when they reach the mayor
of sinusoids they're much too large to enter but they insert these processes called pro platelets
into the sinusoids they dangle in between the the endothelial cells within the the sinusoids
and the flow of blood shears these platelets off and they're floating then in the bloodstream and
what's floating then becomes a thrombus ID or a platelet so it's just a fragment of a mega
carrier blast and these megakaryoblast will shed thousands of these pro platelets that turn into
platelets this is a process which is is supported and modulated by the cytokine thrombopoietin or
TPL for short thrombopoietin like most cytokines exists in very my new levels but it can ramp up
very quickly and so generally within a microliter of blood you might find between 150 to 400 of
these thrombocytes there are going to be more of these so you know probably another 50 to 150 of
them that are sequestered in the spleen for every 150 to 400 that are circulating per microliter of
blood they don't last terribly long so they the generally lasts their lifespan is between one
to two weeks and when complete these thrombocytes are phagocytized by macrophages in the spleen and
so you're just constantly producing romba sites as as you go and more can be recruited with the
help of TPL as needed now these platelets have a couple of functions probably the major function
is to participate in coagulation now it's not just about platelets with coagulation but it's
the combination of platelets and a particular protein called fibrin so fibrin is a soluble
protein that in the presence of enzymes that occur in an area of vascular injury start to
polymerize and so that soluble protein then becomes an insoluble polymer that insoluble
polymer is kind of like a mesh network now that's part of the solution that in and of itself isn't
going to be so sufficient to to plug the hole and what's next is that activated platelets need to
come in now thrombocytes tend to be these kind of amorphous blobs and when they come into contact
with a clotting factor called von Willebrand factor and collagen or if they come into contact
with fibrin they activate and they go from these amorphous blobs to having more kind of extensive
pseudo potus processes and they become enmeshed within this fibrin web and they form a clot to
prevent the escape of more blood now in addition to working in coagulation platelets actually can
help modulate immune responses both innate and adaptive so their role in innate immunity is
somewhat well known they can secrete various modulators of inflammation such as various
cytokines to help create an immune response they can also adhere to various immunoglobulins and be
very anti bacterial in action so they can they can be a partner of the adaptive immune system
as well so they're they're protective in two ways both they protect against exsanguination
as well as protect against pathogens and that leads us to a question here and that is what
blood protein must thrombocytes interact to form a clot is it a albumin B fibrin C immunoglobulin
G or D immunoglobulin M well we can rule out the antibodies there because they're participating in
immune responses that leaves us with two other classes of blood protein albumins are more in
transportation and maintaining osmotic colloidal pressure so that's not right but fibrin is a good
answer because fibrin when it polymerizes is one part one major part of that clot with which
activated platelets are going to interact to create thank you very much for your time