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PBCP- Introduction to physiology and blood > 13. Blood haemostasis and clot lysis > Flashcards

13. Blood haemostasis and clot lysis Flashcards

1
Q

What is haemostasis?

A

The prevention of blood loss

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2
Q

What are the three stages o f haemostasis?

A

Vascular spasms
Platelet plug formation
Coagulation

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3
Q

What are vascular spasms?

A

Immediate vasoconstriction in response to injury

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4
Q

What is platelet plug formation?

A

Platelet adhesion and aggregation

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5
Q

What is coagulation?

A

Blood clotting

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6
Q

What happens during vasoconstriction?

A

Nervous reflexes
Myogenic contraction
Factor from damaged tissue and activated platelets

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7
Q

What happens during platelet plug formation?

A 
Platelets are activated by contact with:
 von Willebrand factor (vWF)
 collagen
 thrombin
 a negatively charged surface

Platelets do not normally stick to the vessel wall

Endothelial surface
Smoothness 
Glycocalyx 
Prostacyclin and NO
thrombomodulin: binds to thrombin
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8
Q

What do the activated platelets release?

A

ADP
Thromboxane A2
Serotonin

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9
Q

What happens in coagulation?

A

A set of reactions in which blood is transformed from a liquid to a gel
Follows intrinsic and extrinsic pathways as well as a common pathway

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10
Q

What is the process of clot retraction?

A 
"Tightening" of clot
Contraction of platelets 
Damaged edges pulled closer together 
Serum squeezed out
Over time the clot is dissolved 
Healing occurs - fibrous tissue
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11
Q

What is the role of calcium ions in the intrinsic and extrinsic pathways?

A

Chelation of Ca2+ prevents clotting in blood samples

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12
Q

How do anticoagulants work in the normal vascular system?

A

Fibrin binds to thrombin

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13
Q

How do anticoagulants work in the normal vascular system?

A

Fibrin binds to thrombin

Heparin and antithrombin III will bind and inactivate thrombin

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14
Q

Describe how aspirin works as an anticoagulant

A

Lecture 23

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15
Q

What is bleeding time?

A

The duration of bleeding after controlled, standardised puncture of the earlobe or forearm

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16
Q

What does bleeding measure?

A

Measures capillary and platelet function

17
Q

What is the clotting time?

A

The time required for blood to clot in a glass tube

18
Q

What does the clotting time reflect?

A

Mainly reflects the time required for generation of thrombin

19
Q

When would the clotting time be prolonged?

A

Prolonged if plasma conc of prothrombin or other clotting factors is low

20
Q

What are causes of hypercoaglation?

A

Endothelial damage

Slowlung flowing or static blood

21
Q

What can hypercoagulation lead to?

A

MI
Stroke
Deep vein thrombosis
Pulmonary embolism

22
Q

What is hypocoagulation?

A

Deficiency of platelets
Deficiency of coagulation factors
Deficiency of vitamin K

PBCP- Introduction to physiology and blood (13 decks)

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