Haemostasis

Question 1

What is haemostasis?

Answer 1

a process to prevent and stop bleeding, meaning to keep blood within a damaged blood vessel (clot?)

Question 2

What happens if the haemostatic mechanism is hyperactive?

Answer 2

Unwanted blood clots (thrombi) may occur

Can block blood vessels and cause tissue death

Question 3

What are the 3 main steps of haemostasis

Answer 3

1) Contraction of injured blood vessel
2) Formation of platelet plug
3) Coagulation of blood

Question 4

What is the texture of the blood vessel lining?

Answer 4

Smooth and invert (unreactive)

Question 5

What happens to the blood vessel smooth muscle when injured and why?

Answer 5

It contracts to reduce blood flow

Question 6

During platelet plug formation, where does the platelet attach to?

Answer 6

The damaged endothelial layer

Question 7

What protein factor is platelet plug formation facilitated by?

Answer 7

The von willebrand factor

Question 8

What does the von willebrand factor do?

Answer 8

forms a bridge between collagen and platelets

Question 9

Which structure reinforces the platelet plug?

Answer 9

a fibrin lattice

Question 10

When does a fibrin lattice occur?

Answer 10

When the plasma protein fibrinogen is converted to fibrin (by the enzyme thrombin)

Question 11

Where are many coagulation factors formed and what nutrient is needed for their synthesis?

Answer 11

Liver

Vitamin K

Question 12

Which enzyme converts fibrinogen to fibrin

Answer 12

Thrombin

Question 13

Name 3 signs that indicate a clotting problem

Answer 13

Primary haemostatic defect (bleeding more than usual):

Sometimes no clinical signs 
Nose bleeds
Vaginal/ penile bleeding
Petechiation
Ecchymosis
Haemorrhages in the skin
Mucous membranes

Question 14

What is thrombin converted from?

Answer 14

Prothrombin - an inactive precursor in the blood

Question 15

How does thrombin convert fibrinogen to fibrin?

Answer 15

Through cascade/ chain reactions - with the help of factor X (prothrombinase) - clotting factors

It is triggered by vessel wall contraction

Question 16

What is Fibrinolysis?

Answer 16

The process which dissolves the blood clot once the injury is healed

Question 17

Why does a fibrin lattice need to form?

Answer 17

To reinforce the platelet plug and ensure it does not give way under pressure

Question 18

How do platelets stick to each other?

Answer 18

They release an active substance that makes their surface sticky

Question 19

Where is prothrombin found?

Answer 19

In the blood

Question 20

What is prothrombin?

Answer 20

A precursor to thrombin found in the blood

Question 21

Why does thrombin need to convert fibrinogen to fibrin?

Answer 21

So fibrin can form a fibrin lattice to reinforce the platelet plug

Question 22

What is fibrin?

Answer 22

a protein

Question 23

What happens if haemostasis does not work properly?

Answer 23

Catastrophic bleeding can occur even after small injury

Question 24

What happens during the coagulation cascade?

Answer 24

Clotting factors (coagulation factors) prompt reactions that activate more coagulation factors

initiated by extrinsic pathway and intrinsic pathway

Question 25

What are the intrinsic and extrinsic pathways?

Answer 25

Extrinsic = coagulation triggered by trauma that releases tissue factors from endothelial cells

Intrinsic = coagulation beginning in the blood stream, triggered by internal damage to vessel wall (exposing endothelial collagen)

Question 26

What is the scientific name for red and white blood cells?

Answer 26

Red = erythrocytes

White = Leukocytes

Question 27

What is the function of platelets?

Answer 27

To clot at the site of injury to prevent blood loss and heal a wound

Question 28

Define Haematopoiesis and Haemostasis

Answer 28

Haematopoiesis = the formation of blood cells

Haemostasis = the mechanism of forming blood clots after injury to stop bleeding