Lecture 1 – hemostasis, coagulation and thrombosis
Primary hemostasis: platelet adhesion and platelet aggregation
Secondary hemostasis: blood coagulation and fibrinolysis
Thrombosis: as a innate defense mechanism (in some cases the defense mechanism works so well it
damages the body.)
The platelet is a very active cell which looks a bit like a bun, it has a granular surface. Platelets are
pretty small and do not have a nucleus, they come from megakaryocytes, they are ensnared off and
taken by the blood stream and then they are circulating in the bun-like shape:
Platelets have different view, they can have different shaped. One of these forms is the star-form
which is a typical activated platelet, with the little “arms” they can grab things.
,If you cut through platelets, it looks a bit like a sponge. It is full with canals which increase the surface
of the platelet so it can actively take up blood coagulation to save for later use and release them very
quickly. The platelet also has little granules which have coagulation factors in them and other factors
like inflammatory molecules, bacteriostatic and antimicrobial molecules.
These granules are very important because they are mobilized very quickly upon activation of the
platelet, its contents then get released in the exterior of the platelet and then can exert their actions
like coagulation etc. to get the reaction done.
Platelets are attached to a fibrin cloth which can be contracted and then you have a good basis for
good healing. The platelets are constantly busy filling little holes, we always have tiny leaks, especially
during inflammation because during inflammation a lot of cells go into the inflamed tissue by exiting
in the vessels which will cause little holes in it which are sealed by platelets.
Thrombopoiesis: the generation of blood platelets
,Megakaryocytes are very interesting because they can grow very big and have a lot of copies of DNA
(up to 128n thus hyperploid). They also contain canals which are important to get a lot of membrane
surface, they extend their membrane into the blood stream and by the action of the blood the (pro-
)platelets are taken away by the blood stream. The snares will turn into real platelets.
You have platelet-producing cells in the bone marrow (primary site) but also in the lungs (platelet-
reservoir, different kind of platelets).
The granules are transported from the megakaryocytes inside through the snares to the platelets. The
granules and contents of the granules are already in the megakaryocytes together with some of the
DNA.
, If you don’t inhibit platelet or you don’t put them in a special buffer and you flick them with your
finger, they will be activated. Platelets are always hyper-responsive, they are always under tension.
You get a stimulus which leads to the activation of the G proteins
The G proteins transfer the signal by a second messenger
The second messenger ends up by the calcium store which releases the calcium into the cell, leading
to very quick rise in calcium concentrations inside the cell
Primary hemostasis: platelet adhesion and platelet aggregation
Secondary hemostasis: blood coagulation and fibrinolysis
Thrombosis: as a innate defense mechanism (in some cases the defense mechanism works so well it
damages the body.)
The platelet is a very active cell which looks a bit like a bun, it has a granular surface. Platelets are
pretty small and do not have a nucleus, they come from megakaryocytes, they are ensnared off and
taken by the blood stream and then they are circulating in the bun-like shape:
Platelets have different view, they can have different shaped. One of these forms is the star-form
which is a typical activated platelet, with the little “arms” they can grab things.
,If you cut through platelets, it looks a bit like a sponge. It is full with canals which increase the surface
of the platelet so it can actively take up blood coagulation to save for later use and release them very
quickly. The platelet also has little granules which have coagulation factors in them and other factors
like inflammatory molecules, bacteriostatic and antimicrobial molecules.
These granules are very important because they are mobilized very quickly upon activation of the
platelet, its contents then get released in the exterior of the platelet and then can exert their actions
like coagulation etc. to get the reaction done.
Platelets are attached to a fibrin cloth which can be contracted and then you have a good basis for
good healing. The platelets are constantly busy filling little holes, we always have tiny leaks, especially
during inflammation because during inflammation a lot of cells go into the inflamed tissue by exiting
in the vessels which will cause little holes in it which are sealed by platelets.
Thrombopoiesis: the generation of blood platelets
,Megakaryocytes are very interesting because they can grow very big and have a lot of copies of DNA
(up to 128n thus hyperploid). They also contain canals which are important to get a lot of membrane
surface, they extend their membrane into the blood stream and by the action of the blood the (pro-
)platelets are taken away by the blood stream. The snares will turn into real platelets.
You have platelet-producing cells in the bone marrow (primary site) but also in the lungs (platelet-
reservoir, different kind of platelets).
The granules are transported from the megakaryocytes inside through the snares to the platelets. The
granules and contents of the granules are already in the megakaryocytes together with some of the
DNA.
, If you don’t inhibit platelet or you don’t put them in a special buffer and you flick them with your
finger, they will be activated. Platelets are always hyper-responsive, they are always under tension.
You get a stimulus which leads to the activation of the G proteins
The G proteins transfer the signal by a second messenger
The second messenger ends up by the calcium store which releases the calcium into the cell, leading
to very quick rise in calcium concentrations inside the cell
