Week 4 - Blood vessels: haemostasis

Question 1

What are the three functions of the blood?

Answer 1

transport, communication, defence

Question 2

What is the basic blood vessel structure?

Answer 2

Question 3

What is the blood supply of the tunica adventitia called?

Answer 3

vasa vasorum

Question 4

What are the three types of artery?

Answer 4

elastic, muscular and arterioles

Question 5

Give examples of elastic arteries

Answer 5

aorta, pulmonary artery

tunica media is broad and elastic with concentric sheets of elastin and collagen

Question 6

What are the differences between elastic and muscular arteries?

Answer 6

muscular - less elastin, broad tunica adventitia, elastin in found in the internal and external elastic lamina

elastic - less smooth muscle, more elastin

Question 7

What are the characteristics of the tunica intima layer of an elastic artery?

Answer 7

single layer of flattened epithelial cells, supporting layer of elastin rich collagen. Has ‘myointimal cells’ that accumulate lipid with ageing - first sign of atherosclerosis.

Question 8

What is the most prominant layer of a vein?

Answer 8

tunica adventitia

has collagen fibres

Question 9

Which is the artery and which is the vein in this histological slide?

Answer 9

vein has smaller muscle wall and the lumen is collapsed

Question 10

What is the difference between a muscular vein and artery?

(muscular artery in picture)

Answer 10

in a muscular vein there is no inner or outer elastic layer

Question 11

What is a severe reduction in the number of platelets called?

Answer 11

thrombocytopenia

Question 12

What is the definition of primary haemostasis?

Answer 12

the formation of a primary platelet plug

Question 13

What is the definition of a secondary haemostasis?

Answer 13

formation of a fibrin mesh by activation of coagulation factors

Question 14

What three chemicals mediate the adhesion of other platelets (platelet aggregation)?

Answer 14

thromboxane A2, ADP and calcium ions

Question 15

What is the mechanism of action of aspirin?

Answer 15

irreversibly inhibits COX which is needed for thromboxane production

aspirin is a type of NSAID but works differently because it irreversibly binds and other NSAIDs reversibly inhibit COX

Question 16

What type of drug is clopidogrel?

Answer 16

ADP receptor antagonist

Question 17

What shape change to platelets undergo when activated?

Answer 17

become more spherical with long thin cytoplasmic processes

Question 18

What two substances normally prevent platelet aggregation?

Answer 18

nitric oxide and prostacyclin

Question 19

What is the sequence of activated factors in the intrinsic pathway?

Answer 19

XII - XIIa (12)

XI - XIa (11)

IX - IXa (9) + VIII (8)

X - Xa (10) + V (5)

count down from 12 but swap 9 and 10 around

9 works with the number below it

10 works with its half

Question 20

What is the first step in the conversion of fibrinogen to fibrin?

Answer 20

removal of fibrinopeptide A (FpA) from fibrinogen by thrombin

Question 21

What happens when all of the fibrinopeptide A has been removed by thrombin?

Answer 21

a two-stranded protofibril is formed

Question 22

What has to occur before protofibres can aggregate laterally?

Answer 22

cleavage of fibrinopeptide B from fibrinogen by thrombin

Question 23

Name three anticoagulants

Answer 23

warfarin, heparin, ancrod

Question 24

What is the most important physiological mechanism for haemostasis in venous vessels?

A) coagulation cascade

B) platelet thrombus

C) anti-thrombin

Answer 24

coagulation cascade

clotting factors are more important in low flow, low pressure vessels

platelets are more important in the arterial circulation where flow is high, blood must be stopped quickly, platelet plug is faster acting

Question 25

What is the first reaction in activation of the extrinsic pathway of the clotting cascade?

Answer 25

tissue factor binds factor VII

(X - Factor)

Question 26

Which factor that is released by endothelial cells causes platelet activation?

A) ADP

B) Histamine

C) Thrombin

D) Prostaglandin I₂ (prostacyclin)

E) Fibrin

Answer 26

A) ADP

Platelets are activated by ADP, thromboxane A₂, calcium and thrombin

ADP is released by damaged endothelial cells

Question 27

What is the role of prostacyclin in blood vessels?

Answer 27

produced by endothelial cells

prevents the formation of a platelet plug by inhibiting platelet activation

effective vasodilator

Question 28

What receptor mediates a strong bond between platelets in a thrombus?

Answer 28

glycoprotein IIb/IIIa

platelets have two main surface glycoprotein receptors: GpIb and GpIIb/IIIa

GpIb is always present and binds to subendothelial collagen via vWF following an injury. This causes acivation of platelets and GpIIb/IIIa is then expressed on platelet surface

Question 29

What two granules are present in platelets?

Answer 29

dense and alpha granules

Question 30

What two cells are the immediate precursors to red blood cells?

Answer 30

reticulocytes and myeloblasts