1: Haemostasis

Question 1

What is haemostasis?

Answer 1

Arrest of bleeding while maintaining vascular patency

Question 2

What is primary haemostasis?

Answer 2

Formation of a fibrin plug at a site of bleeding

Question 3

Which protein is involved in secondary haemostasis?

Answer 3

Fibrin

forms a CLOT around the platelet plug

Question 4

Which two processes keep haemostasis in check after the formation of the fibrin clot?

Answer 4

Fibrinolysis

Anticoagulation

Question 5

Which blood cells form platelets?

Answer 5

Megakaryocytes

Question 6

Are platelets cells?

Answer 6

No

Buds of cytoplasm from megakaryocytes

Question 7

How long do platelets last for?

Why is this clinically relevant?

Answer 7

7 - 10 days

Anti-platelets e.g aspirin are stopped 7-10 days before surgery to avoid bleeding

Question 8

What is the accumulation of platelets at a site of injury called?

Answer 8

Aggregation

Question 9

Platelets ___ to form a plug in ___ haemostasis.

Answer 9

aggregate

primary haemostasis

Question 10

Why do elderly patients bruise easily?

Answer 10

Express less collagen at sites of injury

Leading to less efficient haemostasis

Question 11

What is Vitamin C required to produce?

What is Vitamin C deficiency called?

Answer 11

Collagen

Scurvy

Question 12

What is a reduced number of platelets called?

Answer 12

Thrombocytopaenia

Question 13

What proteins encourage platelet adhesion at the site of an injury?

Answer 13

Collagen

Von Willebrand factor

Question 14

What is an autoimmune disease which causes a rash and thrombocytopaenia?

Answer 14

Immune thrombocytopaenic purpura

Question 15

What symptoms may a patient have if they cannot form a platelet plug?

Answer 15

Bruising

Purpuric rash

Exaggerated bleeding

Question 16

What diseases, causing platelet dysfunction, can cause abnormal bleeding?

Answer 16

Vitamin C deficiency (reduced collagen expression)

Autoimmune thrombocytopaenic purpura

Von Willebrand disease

Question 17

Why do purpuric rashes often appear on the lower limbs?

Answer 17

Oncotic pressure due to gravity

Fluid (inc. blood) squeezed out of capillaries

Elderly / thrombocytopaenic patients cannot stop this “bleeding”

Question 18

What is measured to diagnosed primary haemostasis?

Answer 18

Platelet count

Question 19

What molecules are platelets made of?

Answer 19

Phosphoplipids

Which are negatively charged

Question 20

Which ion is secreted by platelets?

Answer 20

Calcium

Ca2+, binds to -ve phospholipids

Question 21

Which proteins bind to Ca2+ ions, found on the platelet plug, to cause secondary haemostasis?

Answer 21

Clotting factors

Question 22

Which clotting factors initiate coagulation?

Answer 22

Tissue factor and Factor VIIa

Question 23

Which two clotting factors convert prothrombin to thrombin?

Answer 23

Factor V and Factor Xa

Question 24

___ ___ and factor ___ initiate clotting.

Answer 24

Tissue factor and Factor VIIa

Question 25

The factor **V/Xa complex** converts ___ to \_\_\_.

Answer 25

**prothrombin** to **thrombin**

Question 26

**Thrombin** converts ___ to \_\_\_, forming a clot.

Answer 26

**fibrinogen** to **fibrin**

Question 27

What converts **fibrinogen** **to fibrin** to form a clot?

Answer 27

**Thrombin** which is produced from **prothrombin** by **factors V/Xa**

Question 28

Apart from **converting fibrinogen to fibrin** to form a clot, what else does **thrombin** activate during coagulation?

Answer 28

**Factors VIII/IXa** Which reactivates **Factor V/Xa** Which converts more **prothrombin** to **thrombin...**

Question 29

Which protein, generated midway through the clotting cascade, activates **other** clotting factors?

Answer 29

**Thrombin**

Question 30

What is the end product of the clotting cascade?

Answer 30

**Fibrin** forming a clot

Question 31

What is the first clotting factor which binds to the platelet plug?

Answer 31

**Tissue factor \<=\> VIIa**

Question 32

What diseases are caused by a deficiency of a) **Factor VIII** b) **Factor IX**?

Answer 32

**a) Haemophilia A** **b) Haemophilia B**

Question 33

Which **clotting factors are deficient** in a) **Haemophilia A** b) **Haemophilia** **B?**

Answer 33

a) **Factor VIII** (haemophilia A) b) **Factor IX** (haemophilia B)

Question 34

Why might a patient with an **increased reticulocyte count** (e.g haemorrhage, haemolysis) also have **thrombocytosis?**

Answer 34

**Red blood cells** and **megakaryocytes** are derived from the same progenitor cells So when you get an increase in red cell production, you get an increase in platelets

Question 35

What is **disseminated intravascular coagulation?** How is it related to clotting factors? What triggers it?

Answer 35

**Widespread clotting** Depletes clotting factors and platelets, thereby causing **widespread bleeding** **Trauma, sepsis, complicated pregnancy, malignancy, autoimmune disease...** i.e in anyone with widespread bleeding and thrombocytopaenia consider DIC

Question 36

Which protein **breaks down fibrin**?

Answer 36

**Plasmin**

Question 37

What is a notable fibrin breakdown product?

Answer 37

**D dimer**

Question 38

Which protein converts **plasminogen** to **plasmin**?

Answer 38

**Tissue plasminogen activator** (tPA)

Question 39

Where can blood escape in **haemophilia**?

Answer 39

**Epistaxis, menorrhagia, malaena etc...** **Into muscles** **Into joints** (haemarthrosis)

Question 40

What is the mode of inheritance of **haemophilia A and B?**

Answer 40

**X linked recessive**

Question 41

Which blood tests measure time taken for action of a) **tissue factor / factor VIIa?** b) **factor VIII / IXa?**

Answer 41

**a) Prothrombin time (PT or INR)** **b) Activated partial thromboplastin time (APTT)**

Question 42

Which clotting times are useful for a) **warfarin monitoring** b) **heparin monitoring?**

Answer 42

**a) Warfarin monitoring** - **prothrombin time** (factor VII) **b)** **Heparin monitoring** - **APTT** (factor VIII/IXa)

Question 43

What should you look at specifically on examination of someone with a suspected bleeding disorder?

Answer 43

**Lower limbs** - purpura **Mouth** - the same **Eyes** - retinal haemorrhage **Bleeding into muscles and joints**

Question 44

Which **naturally occurring anticoagulant** acts on **thrombin**?

Answer 44

**Anti-thrombin III**

Question 45

Which anticoagulants act on clotting factors?

Answer 45

**Protein C** | (aided by protein S)

Question 46

Which protein does **thrombin** use to **switch functions** and **inhibit** (instead of promote) coagulation?

Answer 46

**Thrombomodulin** switches on Protein C and S

Question 47

Which **inherited disorder** causes a tendency for venous thrombosis?

Answer 47

**Thrombophilia**

Question 48

What is the **most common type** of **inherited thrombophilia**?

Answer 48

**Factor V Leiden**