Pathological thrombosis

Question 1

Thrombosis occurs in 3 predisposing situations

Virchow’s triad consists of:

Answer 1

• Changes in the intimal surface of a vessel
• Changes in the pattern of blood flow
• Changes in the blood constituents

Question 2

Pathological thrombosis occurs

Answer 2

in the absence of a cut or trauma.

Question 3

arteriole =

Answer 3

normal small artery

Question 4

Endothelial cell lines

Answer 4

lumen

Question 5

Endothelial cells make

Answer 5

basal lamina (basement membrane) to ‘sit on’

Question 6

Around basal lamina are

Answer 6

smooth muscle cells

Question 7

Around smooth muscle cells are

Answer 7

interstitial collagen fibres

Question 8

Physiological thrombosis often occurs

Answer 8

after a cut or injury

Question 9

in physiological thrombosis what stops bleeding?

Answer 9

Contraction of the vessel and the thrombus stop the bleeding.
clot fills the defect

Question 10

thrombus is good if

Answer 10

it allows blood flow along vessel to continue.

platelet thrombus

Question 11

in physiological thrombosis, when wound heals

Answer 11

with a scar and blood vessel is repaired.

repaired vessel has normal blood flow.

Question 12

The 3 predisposing situations that may result in thrombus formation are known as

Answer 12

Virchow’s triad

Question 13

Coronary artery thrombosis

Answer 13

Coronary arteries are the main arteries in heart
They supply the heart muscle

Cigarette smoking (and other things such as high lipid in the blood) can also predispose to atheroma in the coronary arteries

Question 14

why is smoking bad for pathological thrombosis

Answer 14

Smoking cigarettes increases the ‘stickiness’ of platelets (they find it easier to aggregate).

This alteration in the properties of blood is a change in blood constituents which is part of Virchow’s triad

Question 15

Atheroma is a

Answer 15

disease of coronary arteries which results in a build up of lipid under the intimal surface.

• The lipid can result in abnormal blood flow – can get both slow and turbulent flow
• Slowed blood flow predisposes to fibrin and platelet clumping

This alteration in the pattern of blood flow is part of Virchow’s triad

Question 16

Lipid (and collagen) can also

Answer 16

rupture through the intimal surface

• Platelets and fibrin are now exposed to an abnormal substance (lipid and collagen) and turbulent flow and are deposited as a thrombus
• The thrombus blocks the lumen of the coronary artery
• Clot can now form in the stagnant blood behind the thrombus

This change in the intimal surface is again part of Virchow’s triad

Question 17

layers of clot when lipid and collagen rupture the through the intimal surface

Answer 17

1st layer = thrombus (platelets and fibrin)
2nd layer = red blood cells trapped in fibrin meshwork so clot forms
3rd layer = This complex structure now protrudes even further into lumen causing more turbulence/slowing so get we get another layer of thrombus

Question 18

Mulitple layers of thrombus and clot =

Answer 18

lines of Zahn (pale layers of thrombus alternating with red layers of clot)

Question 19

Changes in the intimal surface of a vessel example

Answer 19

atheroma lipid coming onto surface

Question 20

Changes in the pattern of blood flow example

Answer 20

a bulge of atheroma changing the flow of blood

Question 21

Changes in the blood constituents example

Answer 21

smoking making it more likely that platelets aggregate

Question 22

Consequences of a thrombus blocking an artery are bad:

Complete obstruction

Answer 22

leads to no flow beyond blockage

Question 23

Consequences of a thrombus blocking an artery are bad:

partial obstruction

Answer 23

leads to decreased flow beyond blockage.

- The tissue supplied by this artery receives less blood flow

Question 24

ischaemia =

Answer 24

tissue supplied by artery that receives less blood flow

Question 25

hypoxia =

Answer 25

if severe enough ischaemia leads to decreased oxygenation of tissues.
tissue is said to be ischaemic and ischaemic heart tissue is often painful

Question 26

when hypoxia occurs

Answer 26

it can lead to localised area of tissue dying

Question 27

infract/infraction =

Answer 27

localised area of dead tissue.

necrosis as a result of ischaemia

Question 28

necrosis =

Answer 28

process of tissue dying.

Question 29

ischaemia =

Answer 29

ischaemic death

Question 30

Coronary artery thrombosis can lead to

Answer 30

infraction in brain tissue or heart

Question 31

Mesenteric artery thrombosis can lead to

Answer 31

infraction in gut

Question 32

Embolism =

Answer 32

A mass of material moving in the vascular system and able to become lodged in a vessel and block its lumen

Question 33

most emboli are derived from

Answer 33

thrombi or clots.

They break off and go elsewhere in the circulation

Question 34

thromboembolism =

Answer 34

When thrombi/clots embolise

Question 35

Commonest example of thromboembolism

Answer 35

Pulmonary embolism (lungs)

Question 36

How does pulmonary embolism occur?

Answer 36

• Sluggish flow in leg veins leads to thrombosis and clot formation
• Part of thrombus (and clot) breaks off and travels up vein
• Embolus passes into inferior vena cava, then right heart, then pulmonary trunk, and lodges in pulmonary artery branch
• Embolus blocks pulmonary artery and get pulmonary infarct

Question 37

Other forms of embolism:

Marrow embolism

Answer 37

Fracture a leg —> marrow enters ruptured vein —> marrow embolises to lung vessels

Question 38

Other forms of embolism:

Air embolism

Answer 38

Knife wound to neck.

Air enters vein —> air embolises to heart