(15) Hemostasis (Karius)

Question 1

What is this?

What is it derived from?

Answer 1

A Platelet

Cell fragment derived from megakaryocyte

Question 2

Amine terminal of thrombopoietin (TPO) is similar to…

Answer 2

Erythropoietin (EPO)

Question 3

Function of Thrombopoietin?

Answer 3

Tells bone marrow to make more platelets

Question 4

Platelets bind _________ ( ) receptor

Answer 4

Thrombopoietin (mpl)

Question 5

Describe what happens with TPO secretion when there are:

High number of platelets

Answer 5

• Lots of TPO bound to mpl receptor on platelets
• Internalize TPO and destroy it
• Not much free to act on megakaryocytes

Question 6

Describe what happens with TBO secretion when there are:

Low number of platelets

Answer 6

• Little bound to platelets
• Not being destroyed
• Lots free

Question 7

Why does it make sense to use platelet number directly to control thrombopoietin secretion?

Answer 7

Negative feedback

As free levels of platelets shift rapidly, so do TPO levels

Question 8

TPO acts on _____ cell lines

Answer 8

ALL

*but particularly RBCs

Question 9

Describe what happens if a mutation in the TPO receptor were to occur:

Answer 9

Polycythemia vera

Platelets are unable to internalize and destroy the TPO, so its action becomes continuous

Question 10

What do platelets contain?

Answer 10

• Actin and myosin
• Mitochondria
• Remnants of ER
• COX1
• Fibrin stabilizing factor
• Platelet-derived growth factor
• Serotonin (5-HT) –> leads to headaches, vasoconstrictor

Question 11

Platelets express:

Answer 11

Glycoproteins (when activated = sticky)

Phospholipids

Receptors for collagen

Question 12

SUMMARY SLIDE: Thrombocytes

Describe the production of platlets

Answer 12

Question 13

What organs secrete TPO?

Answer 13

Liver

and

Kidney

Question 14

What is the receptor for thrombopoiesis?

Answer 14

MPL

Question 15

What are the 4 steps for hemostasis?

Answer 15

1. Vascular spasm
2. Formation of platelet plug
3. Formation of blood clot
4. Repair of damage

Question 16

SUMMARY SLIDE:

Describe the initiation and function of vascular spasm

Answer 16

Question 17

What causes the formation of a platelet plug?

Answer 17

When you damage a blood vessel, expose the collagen

Platelets bind to collagen in a 2 step process

1. Von Willebrand Factor (bridge b/w collagen and platelet)
2. Binding of platelet receptor (integrin) to collagen -> extends podocytes, swells

Question 18

SUMMARY SLIDE

Describe the formation and function of the platelet plug

Answer 18

Question 19

Label the blood clot

Answer 19

Question 20

LO

Describe the role of platelets in clot stabilization

Answer 20

Question 21

How do you get rid of the clot?!

Answer 21

Plasminogen !!!!

(made by liver, floating in plasma, not active form)

Question 22

How do you activate plasminogen?

Answer 22

Tissue plasminogen activator

*released by damaged tissue

Question 23

LO

Describe how clots are removed

Answer 23

Question 24

Platelets will activate if you move them over a ______ surface

Answer 24

Rough

Question 25

LO

Describe the systems which limit clotting

Answer 25