Haemostasis 1: Platelets

Question 1

What is the meaning of Haemo-Stasis?

Answer 1

Blood Stop

Question 2

What is the difference between Haemo-Stasis and Homeo-stasis?

Answer 2

Haemo-Stasis refers to blood stopping, while Homeo-stasis refers to self-regulating processes maintaining stability for survival.

Question 3

What are the three key steps in the process of bleeding?

Answer 3

• Vessel constriction
• Platelet activation and plug formation
• Coagulation cascade activated

Question 4

What are the two main components involved in haemostasis?

Answer 4

• Platelets
• Coagulation

Question 5

What happens when there is too much platelet stickiness?

Answer 5

Platelets stick to damaged endothelium, leading to arterial thrombosis.

Question 6

What are the consequences of too little platelet stickiness?

Answer 6

Bleeding from mucosal surfaces, gut bleeds, menorrhagia, bruising.

Question 7

What is coagulation in the context of haemostasis?

Answer 7

The jelly component of haemostasis, primarily consisting of fibrin.

Question 8

What can occur if there is too much coagulation?

Answer 8

Clot formation in veins, such as deep vein thrombosis.

Question 9

What can occur if there is too little coagulation?

Answer 9

Bleeding disorders, such as haemophilia.

Question 10

What is the lifespan of platelets in blood?

Answer 10

About 10 days.

Question 11

What is the role of healthy arterial endothelium?

Answer 11

Acts like ‘teflon’ to prevent platelet activation.

Question 12

What do normal endothelial cells secrete to inhibit platelet activation?

Answer 12

• PGI2 (prostacyclin)
• NO (nitric oxide)

Question 13

What is von Willebrand Factor’s role in platelet function?

Answer 13

It facilitates platelet adhesion and activation.

Question 14

What happens to platelets upon activation?

Answer 14

Microtubules contract and granules are released.

Question 15

What are some key components released from activated platelet granules?

Answer 15

• ADP
• Serotonin
• Von Willebrand Factor
• Fibrinogen
• Platelet-derived growth factor

Question 16

What is the significance of the αIIβ3 (GPIIb/IIIa) receptor in platelets?

Answer 16

Converts to a high-affinity state for fibrinogen binding during platelet activation.

Question 17

How does aspirin affect platelet function?

Answer 17

It irreversibly inhibits COX-1, preventing thromboxane production.

Question 18

What is the daily platelet production in an average adult?

Answer 18

Approximately 1 x 10^11.

Question 19

What is thrombocytopenia?

Answer 19

A condition characterized by low platelet counts.

Question 20

What are the causes of low platelet counts?

Answer 20

• Reduced marrow production
• Immune destruction
• Consumption
• Genetic factors
• Splenomegaly

Question 21

What are petechiae?

Answer 21

Small pinpoint bleeds due to low platelet counts.

Question 22

What do large areas of purpura indicate?

Answer 22

They are called ecchymoses, often due to low platelet counts.

Question 23

What is the normal platelet count range?

Answer 23

150-400 x 10^9/L.

Question 24

What should be done when platelet counts drop below 50 x 10^9/L?

Answer 24

Stop all anticoagulants/antiplatelet agents.

Question 25

What is the effect of clopidogrel on platelets?

Answer 25

It blocks ADP receptors, reducing platelet activation.

Question 26

What is the Platelet Function Analyser (PFA) test used for?

Answer 26

To measure platelet function in vitro.

Question 27

What are the signs of inherited platelet function defects?

Answer 27

* Increased bruising * Dental/surgical bleeding * Heavy menstrual periods

Question 28

Name a common inherited platelet function defect.

Answer 28

Von Willebrand disease.

Question 29

What is the consequence of using non-steroidal anti-inflammatory drugs (NSAIDs) on platelets?

Answer 29

They act as reversible inhibitors of COX-1, affecting platelet function.

Question 30

What is the impact of selective serotonin reuptake inhibitors (SSRIs) on platelets?

Answer 30

They may impair platelet function mildly.

Question 31

What do normal endothelial cells secrete to inhibit platelet activation?

Answer 31

PGI2 (prostacyclin) and NO (nitric oxide) ## Footnote PGI2 inhibits platelet activation, while NO dilates blood vessels.

Question 32

What happens to platelets when the blood vessel lining is damaged?

Answer 32

Platelets stick to the damaged endothelium and underlying collagen and von Willebrand Factor.

Question 33

What do activated platelets secrete to recruit more platelets?

Answer 33

ADP and thromboxane.

Question 34

What is the role of fibrin in hemostasis?

Answer 34

Reinforces the platelet plug.

Question 35

List key components released from platelet granules upon activation.

Answer 35

* ADP * Serotonin * Von Willebrand Factor * Fibrinogen * Platelet-derived growth factor.

Question 36

Name the key platelet receptors involved in adhesion and activation.

Answer 36

* vWF * Collagen * ADP * Thrombin * Thromboxane (TXA2) * Fibrinogen.

Question 37

True or False: Thromboxane A2 is generated during platelet activation.

Answer 37

True.

Question 38

What percentage of platelets are sequestered in the spleen at any one time?

Answer 38

Approximately 25%.

Question 39

What is the normal range for platelet levels?

Answer 39

150-400 x 10^9/L.

Question 40

What is thrombocytopenia?

Answer 40

Low platelet count.

Question 41

What are small pinpoint bleeds called?

Answer 41

Petechiae.

Question 42

List some causes of low platelet counts.

Answer 42

* Reduced marrow production * Immune destruction * Consumption * Genetic factors * Splenomegaly.

Question 43

What is the effect of aspirin on platelet function?

Answer 43

Irreversible inhibitor of COX-1, preventing production of thromboxane.

Question 44

What type of drug is clopidogrel?

Answer 44

ADP receptor blocker.

Question 45

What stimulates the production of platelets?

Answer 45

Thrombopoietin (TPO).

Question 46

What is a common consequence of low platelet function?

Answer 46

Increased bleeding and bruising.

Question 47

What is von Willebrand disease?

Answer 47

An inherited condition that causes low levels of von Willebrand factor.

Question 48

What test is used to assess platelet function?

Answer 48

PFA (Platelet Function Analyser) test.

Question 49

Fill in the blank: The normal time for capillary occlusion by a platelet plug in the PFA test using collagen-adrenalin is _____ seconds.

Answer 49

82-160.

Question 50

What are acquired platelet function defects often caused by?

Answer 50

* Anti-platelet drugs * Aspirin * Clopidogrel * Non-steroidal anti-inflammatory drugs.

Question 51

What is the typical response time for platelet levels after significant blood loss?

Answer 51

Reactive changes occur over time.