(15) Hemostasis (Karius) Flashcards
What is this?
What is it derived from?
A Platelet
Cell fragment derived from megakaryocyte
Amine terminal of thrombopoietin (TPO) is similar to…
Erythropoietin (EPO)
Function of Thrombopoietin?
Tells bone marrow to make more platelets
Platelets bind _________ ( ) receptor
Thrombopoietin (mpl)
Describe what happens with TPO secretion when there are:
High number of platelets
- Lots of TPO bound to mpl receptor on platelets
- Internalize TPO and destroy it
- Not much free to act on megakaryocytes
Describe what happens with TBO secretion when there are:
Low number of platelets
- Little bound to platelets
- Not being destroyed
- Lots free
Why does it make sense to use platelet number directly to control thrombopoietin secretion?
Negative feedback
As free levels of platelets shift rapidly, so do TPO levels
TPO acts on _____ cell lines
ALL
*but particularly RBCs
Describe what happens if a mutation in the TPO receptor were to occur:
Polycythemia vera
Platelets are unable to internalize and destroy the TPO, so its action becomes continuous
What do platelets contain?
- Actin and myosin
- Mitochondria
- Remnants of ER
- COX1
- Fibrin stabilizing factor
- Platelet-derived growth factor
- Serotonin (5-HT) –> leads to headaches, vasoconstrictor
Platelets express:
Glycoproteins (when activated = sticky)
Phospholipids
Receptors for collagen
SUMMARY SLIDE: Thrombocytes
Describe the production of platlets
What organs secrete TPO?
Liver
and
Kidney
What is the receptor for thrombopoiesis?
MPL
What are the 4 steps for hemostasis?
- Vascular spasm
- Formation of platelet plug
- Formation of blood clot
- Repair of damage
SUMMARY SLIDE:
Describe the initiation and function of vascular spasm
What causes the formation of a platelet plug?
When you damage a blood vessel, expose the collagen
Platelets bind to collagen in a 2 step process
- Von Willebrand Factor (bridge b/w collagen and platelet)
- Binding of platelet receptor (integrin) to collagen -> extends podocytes, swells
SUMMARY SLIDE
Describe the formation and function of the platelet plug
Label the blood clot
LO
Describe the role of platelets in clot stabilization
How do you get rid of the clot?!
Plasminogen !!!!
(made by liver, floating in plasma, not active form)
How do you activate plasminogen?
Tissue plasminogen activator
*released by damaged tissue
LO
Describe how clots are removed
Platelets will activate if you move them over a ______ surface
Rough
