Primary and secondary hemostasis

Question 1

Main goal of primary hemostasis is to

Answer 1

form a platelet plug

Question 2

Steps in primary hemostasis

Answer 2

1. Vasoconstriction
2. PLatelet adhesion
3. Platelet activation
4. Platelet aggregation

Question 3

How does vasoconstriction occur

Answer 3

1. Nerve reflexes tell smooth muscle of blood vessels to contract
2. Endothelin from endothelial cells counteracts action of nitric oxide, a vasodilator and prostacyclin

Question 4

How does platelet adhesion occur

Answer 4

platelets adhere to the site of injury using von willebrand factor as the glue.

Question 5

What does von willebrand factor do

Answer 5

Glue that attaches platelets to blood vessel wall

Question 6

Why do platelets not initially attach to vessel wall surface

Answer 6

Prescence of prostacyclin and nitric oxide preven this from happening

Question 7

Source of von willebrand factor

Answer 7

Blood

Endothelial cells

Question 8

How does von willebrand factor bind platelets to vessel wall

Answer 8

vWf bind to subendothelial collagen of damaged vessel wall and GP1b receptor on platelets

Question 9

What happens in platelet activation

Answer 9

The platelet changes shape

Inactive GP2b/3a platelet receptors are made active by platelet activation and changes its shape

Degranulation occurs

Question 10

What is involved in degranulation

Answer 10

Release of granules in platelets into blood

Question 11

Types of granules released and what they do

Answer 11

Alpha granules- contain fibrinogen, useful for secondary hemostasis

Dense/ Delta granules - secrete serotonin, Adenosine diphosphate and calcium

Question 12

Function of serotonin

Answer 12

Vasoconstriction

Question 13

Function of adenosinediphosphate

Answer 13

Promotes platelet aggregation

Question 14

Function of calcium

Answer 14

Stabilizes the clot formed in secondary hemostasis

Question 15

Platelet aggregation is primarily mediated by

Answer 15

GP2b/3a

Question 16

What happens in platelet aggregation

Answer 16

Platelet activation causes GP2b/3a to be activated and change shape–>GP2b/3a binds to fibrinogen—> fibrinogen binds to many other GP2b/3a receptors on other platelets—. clumping and formation of platelet plug

Question 17

Goal of secondary hemostasis

Answer 17

Formation of fibrin mesh to stabilize platelet plug produced in primary hemostasis through a coagulation cascade

Question 18

What is involved in the coagulation cascade

Answer 18

A series of events that convert inactive enzymes to active enzymes

Question 19

Coagulation cascade is triggered by

Answer 19

Vessel wall injury

Question 20

Factors involved in intrinsic pathway in coagulation cascade

Answer 20

I,II,XII,XI,IX,VIII. It is activated by internal trauma i.e trauma to blood cells directly/ exposure of blood to collagen

Question 21

What activates extrinsic pathway

Answer 21

vessel wall injury

injury to tissues

Question 22

Factors involved in extrinsic pathway

Answer 22

factor VII

Question 23

Both intrinsic and extrinsic pathway lead to

Answer 23

Common pathway which involves activation of factor X

Question 24

Function of factor X

Answer 24

Conversion of prothrombin to thrombin

Question 25

Thrombin converts

Answer 25

Fibrinogen to fibrin clot

Question 26

Fibrinolysis

Answer 26

A process that leads to the breakdown of clots in order to prevent them from growing

Question 27

Fibrin is lysed into

Answer 27

fibrin degradation products or D dimers

Question 28

Fibrinolysis process

Answer 28

At the site of clot formation, plasminogen is activated and converted to plasmin to limit it to the site of clot formation.

Plasmin will cause the dissolution of fibrin meshwork

Question 29

This substances enhances activity of plasminogen

Answer 29

Tissue plasminogen activator

Factor XIa and factor XIIa

Question 30

Plasmin is inhibited by

Answer 30

alpha antiplasmin

alpha macroglobulin