03 - Blood: platelets & haemostasis

Question 1

Define haemostasis…

Answer 1

The arrest of bleeding from a broken blood vessel

Question 2

Platelets are anuclear (True / False)

Answer 2

True

Platelets are anuclear cell fragments

Question 3

Contraction of the spleen triggered by the SNS releases stored…

Answer 3

Platelets

Question 4

Platelets have a lifespan of…

Answer 4

7-10 days (short)

Question 5

At the end of their lifespan, platelets are apoptosed and phagocytosed in the (2)…

Answer 5

Liver and spleen

Question 6

Thrombopoetin stimulates the production of…

Answer 6

Megakaryoblasts

Question 7

Megakaryoblasts are large cells derived from…

Answer 7

Repeated mitosis of the myeloid cell line without cytokinesis

Question 8

Platelets have an exterior coat rich in…

Answer 8

Glycoproteins

Question 9

The exterior coat of platelets is involved in (3)…

Answer 9

• Adhesion
• Aggregation
• Activation

Question 10

Platelets contain 2 types of granule…

Answer 10

• Alpha

* Delta (dense)

Question 11

Alpha granules contain…

Answer 11

Clotting mediators

Factors V, VIII; VWF; fibrinogen

Question 12

Dense granules contain…

Answer 12

ADP, Ca2+ and Seratonin

Question 13

Low platelet count is known as…

Answer 13

Thrombocytopenia

Question 14

Thrombocytopenia may be caused by…

Answer 14

Autoimmunity or drugs

Question 15

Thrombotic thrombocytopenic purpura is a rare condition in which…

Answer 15

Small clots reduce platelet numbers

Question 16

The first step in the process of haemostasis is…

Answer 16

Vascular spasm

Question 17

Describe the events of vascular spasm (haemostasis step 1)…

Answer 17

Release of 5HT and ADP from damaged cells and platelets leads to constriciton of smooth muscle. This reduces blood flow and pushes together endothelial cuts which have become sticky

Question 18

Step 2 in haemostasis is…

Answer 18

Platelet plug formation

Question 19

Von Willebrand Factor (VWF) activates…

Answer 19

Platelets

Question 20

Platelet factors attract platelets to the site of the damage, which aggregate to form a…

Answer 20

Plug

Question 21

The plug formed in step 2 of haemostasis is sealed by (3)…

Answer 21

• Compaction
• Further vasoconstriction
• Clotting cascade

Question 22

Step 3 in haemostasis is…

Answer 22

Coagulation (blood clotting)

Question 23

The blood clot strengthens and supports…

Answer 23

The plug

Question 24

Clotting steps (2)…

Answer 24

• Fibrinogen is converted to fibrin by thrombin (Factor IIa protease)
• Fibrin (monomer) is polymerised by Ca2+ and Factor VIIIa

Question 25

The clotting cascade is divided into 3 parts…

Answer 25

The intrinsic and extrinsic pathways, which converge in the common pathway

Question 26

The overall process of clotting involves 2 phases…

Answer 26

1. Initiation (tissue exposure triggers extrinsic pathway, small amount of thrombin produced)
2. Amplification (thrombin feeds back, activating intrinsic pathway)

Question 27

Define thrombus…

Answer 27

A blood clot within a blood vessel or the heart

Question 28

Define embolus…

Answer 28

A detached mass able to travel through blood vessels

Question 29

Define embolism…

Answer 29

The lodging of an embolus

Question 30

Define thromboembolism…

Answer 30

A blockage caused by a dislodged blood clot which has travelled from another site in the circulation

Question 31

Contusion is more comonly known as…

Answer 31

Bruising

Question 32

After coagulation, clot retraction has the effect of…

Answer 32

Bringing wound edges closer together

Question 33

Clot retraction occurs via the contraction of…

Answer 33

Actin and myosin fibres within the platelets