Lecture 5: Blood Clotting Flashcards Preview

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Flashcards in Lecture 5: Blood Clotting Deck (89)
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1

What gives rise to platelets?

megakaryocytes

2

___ are needed for blood clotting

platelets

3

How do megakaryocytes give rise to platelets?

Edges of megakaryocyte break off to form platelets (cell fragments)

4

Megakaryocytes are...

giant cells with many copies of DNA in the nucleus

5

Half life of platelets?

10 days

6

____ increases platelet numbers by...

thrombopoietin
stimulating production of platelets

7

How is blood clotting regulated? (3 phases)

1. vascular phase
2. platelet phase
3. coagulation phase

8

Vascular phase

Exposed collagen & tissue factors cause vasoconstriction of the damaged blood vessel. Vasoconstriction minimizes blood loss.

9

Vascular phase controlled by...

nervous system & muscles (neurogenic & myogenic control)

10

Vasoconstriction in vascular phase prolonged by...

1. Serotonin
2. Endothelin-1
3. Thromoboxane A2

11

Platelet phase

1. Collagen exposed to blood stream; bind platelets passing by in the blood
2. Factors released from trapped platelets attract more platelets
3. Platelets aggregate to form plug

12

What makes von Willebrand factor?

endothelial cells
platelets

13

What does von Willebrand factor bind to?

collagen
platelets

14

What are the factors released from platelets?

ADP
PAF (platelet activating factor)
serotonin
thromboxane

15

When are factors released from platelets?

during platelet phase

16

What does serotonin and thromboxane cause?

vasoconstriction

17

What do activated platelets look like?

spiky outer surface

18

Purpose of activating platelets?

they can adhere to each other better

19

What do inactivated platelets look like?

disk-like cell fragments

20

What prevents platelet adhesion/activation during normal situations?

Vasodilators:
NO
Prostacyclin

21

What releases NO and prostacyclin

endothelium

22

Prostacyclin is made up of...

Prostaglandin I2, PGI2

23

Why is aspirin given after mild heart attacks?

Precursor for thromboxane is arachidonic acid.
Enzyme cyclooxygenase cleaves ADA -> PGH2 -> thromboxane.
Aspirin stops CO activity, so thromboxane can't be made.
Since thromboxane is used to vasoconstrict & aggregate platelets, these don't happen as easily.

24

Function of von Willebrand factor?

- link platelet with collagen
- draw platelet into exposed collagen area
- keep VII in circulation longer

25

What happens during vascular phase?

vasoconstriction

26

What happens during platelet phase?

Platelets are actively trying to stop bleeding (loose platelet plug)

27

What happens during coagulation phase?

- Proper blood clot forms via coagulation cascade
- Fibrinogen -> fibrin

28

Fibrin

Long strand of fibre that reinforces loose platelet plug

One piece of fibrinogen

29

Inactive form of fibrin

fibrinogen

30

What do all the factors released from platelets cause?

platelet aggregation