Vascular Spasm and the Plt Plug

Question 1

What are the 4 steps of hemostatic mechanism

Answer 1

1. Vascular spasm
2. Formation of platelet plug
3. Formation of the fibrin clot
4. Fibrinolysis

Question 2

Immediately following vascular injury, _______ contracts to reduce blood flow to the area.

Answer 2

the vessel (tunica media)

Question 3

Vascular vasospasm serves what 2 functions

Answer 3

1. Reduces blood loss
2. Helps procoagulants remain in the affected area so that they can do their job

Question 4

What are the three steps of platelet plug formation?

Answer 4

1. Adhesion
2. Activation
3. Aggregation

Question 5

Describe adhesion as a step of platelet plug formation

Answer 5

1. Endothelial injury exposes collagen
2. Platelet adhere to collagen via Gp Ia and Gp VI receptors
3. Von Willebrand factor (vWF) is synthesized and released from the endothelium
4. Vfw binds to the GpIB receptor on the platelet and anchors the platelet to the sub endothelium.

Question 6

______________ is a disease of platelet adhesion

Answer 6

Von willebrand disease

Question 7

Describe activation as a step of platelet plug formation

Answer 7

1. Exposed collagen at site of injury activates platelets.
2. Activated platelet release ADP and thromboxane A2 which activate nearby platelet and. facilitate plt aggregation.
3. Activated platelet contract and extrude the contents of their alpha granules ( fibrinogen, fibronectin, vWF, platelet factor 4 and platelet growth factor).
4. Activated plt become swollen , irregularly shaped “sticky” mass => Helps adhere to site of injury.
5. Activated plts express two glycoproteins on their surface -GpIIb and GpIIIa.

Question 8

Besides collagen, ____________ also plays an important role in plt activation

Answer 8

Thrombin

Question 9

TxA2 has an additional role of acting as ___________ besides plt activation.

Answer 9

Vasoconstrictor

Question 10

Describe aggregation as a step of platelet plug formation

Answer 10

1. The GpIIb/IIIa receptor complex links activated plts together
2. TxA2 and ADP are required to configure GpIIb/IIIa to accept fibrinogen

Question 11

Activation of the clotting cascade is not required to stop bleeding in _______ injuries.

Answer 11

Microinjuries.

Platelet plug is enough

Question 12

For ___________ injuries the plt plug creates a loose fragile and temporary fix that requires the coagulation process to form fibrin threads that strengthen the clot.

Answer 12

Significant Vascular injury.

Question 13

List 3 steps required o produce a plt plug

Answer 13

1. Adhesion
2. Activation
3. Aggregation

Question 14

Von Willebrand factor binds to platelet during which step?

Answer 14

Step 1: Adhesion

Question 15

How does the injured blood vessel initially activate the platelet plug

Answer 15

Endothelial injury exposes collagen. Exposed collagen at the site of injury activates platelets.