Hemostasis Flashcards
Platelets are derived from
GM-CSF thrombo
—> Megakaryocytes*
*hematopoietic linaege
Another name for platlets
Thrombocytes
When are platelets formed
They are active when they a fragments off the megakaryocytes
Normal levels of platelets
150,000-450,000 ul^3
What do platelets contain
Actin, myosin, thrombostatin, mitochondria, peroxioomes, COX2, Fribrin
2 granules
2 granules that platelets have
- a-granules : store Von Willebrand factor, fibrinogen, factor 5 (clotting)
- dense-core granules : store ATP, ADP, HT’5, Ca+2
Megakaryocytes and platelets take up what
Fibrinogen that they secrete in the liver for Hemostasis
3 steps for platelets
Adhesion
Activation
Aggregation
What regulates platelet formation
Thrombopoietin (TPO) made in liver and kidney
The C-terminal if it prolongs life of platelet
* increase production and function of hematopoietic stem cells and platelets
How does TPO act
It binds to the c-MPL (CD110) receptor on the Megakaryocytes
Low platelet count effect on TPO
High free TPOs
C-MPL is not internalized and degraded
High platelet count effect on TPO
Low free TPOs and c-MPL receptor is internalized and degraded
4 steps to healing injury
- Vascular Spasm : severed vessel
- Formation of platelet plug : Platelet agglutinate + fibrin appears
- Formation of blood clot
- Repair of Damage : clot retracts
What is vasospasm
Disrupt BF and keep it above the injury = avoid more blood loss
4 things that contribute to vasospasm
- Myogenic : reflex from damage to SM
- Platelet factor : serotonin, thromboxane A2
- Release of molecules from endothelial BV cells
- Neural reflex from pain or injury