Circulation 2: Pathological Thrombosis and Embolism

Question 1

Describe Virchow’s triad.

Answer 1

Virchow’s triad states that there are 3 disposing causes of thrombosis:
1) Changes in the intimal surface of the lumen
2) Changes in the pattern of blood flow
3) Changes in the constituents of the blood

Question 2

Define “ischemia”

Answer 2

Poor blood supply to a target tissue.
Tissue said to be “ischaemic)

Question 3

Define “hypoxia”

Answer 3

Hypoxia occurs if the ischaemia is severe enough.
= Lack of oxygen to tissue
Severe hypoxia

Question 4

Define “anoxia”.

Answer 4

Anoxia is when the body or brain loses all of its oxygen, this is as a result of hypoxia.
When hypoxia turns into anoxia, the brain, kidneys and heart can stop functioning properly

Question 5

Describe necrosis

Answer 5

Tissue death from hypoxia.

Question 6

Describe infarction

Answer 6

Infarction is the death of tissue as a result of ischaemia.
Ischaemia leads to hypoxia leads to infarction

Question 7

Describe the process by which a pulmonary embolism occurs.

Answer 7

DVT = deep vein thrombosis.
Sluggish flow in leg veins leads to thrombosis and clot formation.
Part of thrombus (and clot) break off and travel up vein (because it has become unstable).
Embolus passes up from vein of lower limb, into abdomen, up through inferior vena cava, opens into right atrium, to right ventricle, into pulmonary trunk, it then lodges in a pulmonary branch - blocking it.

Size of area of damage (infarction) depends on size of embolus and where is gets lodged.

Could potentially lodge in the bifurcation of the pulmonary

**Common cause of sudden death

Question 8

Define an atheroma

Answer 8

Atheroma (atherosclerosis) the major cause of coronary artery disease.
Accumulation of platelets, fats, lipids stick to the endothelial surface and cause plaque within the vessel.

Question 9

Outline an example of thrombosis from changes in the intimal surface of the lumen.

Answer 9

Atheroma lipid (and collagen) rupture through the intimal surface. Exposed to abnormal substances and flow.
= formation of a thrombus, blocking the lumen of the coronary artery.
Clot (RBCs and fibrin meshwork) then forms in the stagnant blood behind the thrombus.

Question 10

Outline an example of thrombosis from changes in the blood constituents

Answer 10

Example: smoking of cigarettes.
Increases the stickiness of platelets, so they can aggregate better = more likely that a thrombus will form

Question 11

Outline an example of thrombosis from changes in the pattern of blood flow.

Answer 11

The atheroma lipid
Causes vessel to have irregular shape, lesser
diameter, irregular blood flow.
= predisposition to thrombosis, and platelet clumping

Question 12

Describe the lines of Zahn.

Answer 12

The alternate pale and dark streaks of thrombus layers (pale) and clot (red).

Question 13

Describe the coronary arteries.

Answer 13

Originate just at the aortic valve.
There is a right and a left coronary artery.
Both supply the major muscles of the heart.
So, blockage of these arteries by atherosclerosis cabn lead to angina (chest pain) and myocardial infarction.

Question 14

Describe an embolism.

Answer 14

Is a mass of material in the vascular system that has the potential to cause a blockage
-Most are derived from thrombi or clots = thromboembolism (arterial or venous).
They break off and go elsewhere in the circulation.

Question 15

Describe ischaemia as a symptom of angina.

Answer 15

Painful ischaemic heart tissue, chest pain.