2.7 Pathology of Cardio Vascular Disease

Question 1

Describe the process of atherosclerosis.

Answer 1

Atherosclerosis is the accumulation of fatty material (consisting mainly of cholesterol, fibrous material and calcium) beneath the endothelium of an artery. This forms an atheroma or plaque beneath the endothelium.

Question 2

Explain the impact of atherosclerosis on arteries, blood pressure and its link to cardiovascular diseases (CVD)

Answer 2

As an atheroma grows the artery thickens and loses its elasticity. The diameter of the artery lumen also becomes reduced, this restricts the blood flow resulting in increased blood pressure. Blood pressure is increased because the heart muscles have to work harder to push the blood through the restricted space

Question 3

Consequently, atherosclerosis is the root cause of various cardiovascular diseases such as

Answer 3

Angina
· Heart attack
· Stroke
· Peripheral vascular disease (PVD).

Question 4

step one of the formation of a blood clot (thrombus)

Answer 4

An atheroma may rupture damaging the endothelium.

Question 5

Step two of the formation of a blood clot (thrombus)

Answer 5

2. The damage to the endothelium releases clotting factors that activate a cascade of reactions resulting in the conversion of the enzyme prothrombin to its active form thrombin.

Question 6

Step three of the formation of a blood clot (thrombus)

Answer 6

3. Thrombin then causes molecules of the plasma protein fibrinogen to form threads of fibrin.

Question 7

Step four of the formation of a blood clot (thrombus)

Answer 7

4. The fibrin threads form a meshwork that clots the blood, seals the wound and provides a scaffold for the formation of scar tissue.

Question 8

What is the formation of a clot referred to as

Answer 8

The formation of a clot (thrombus) is referred to as thrombosis.

Question 9

State the possible consequences of thrombosis

Answer 9

The possible consequences of thrombosis are :
· Heart attack / Myocardial infarction (MI) - A thrombosis in a coronary artery.
· Stroke - A thrombosis in an artery in the brain.
In both cases, the cells are deprived of oxygen leading to death of the surrounding tissues.

Question 10

State the difference between a thrombus and an embolus

Answer 10

A thrombus blocks a blood vessel at the site of its formation. An embolus is formed when a thrombus (blood clot) breaks loose from its original site of formation to form a mobile clot. The mobile blood clot is called an embolus. This embolus will travel through the bloodstream until it eventually blocks a blood vessel at a site remote from its original formation site.

Question 11

State the definition of peripheral vascular disorders (PVD)

Answer 11

Peripheral vascular disease (PVD) is narrowing of the arteries other than those of the heart or brain.

Question 12

State the causes of peripheral vascular disorders (PVD’s)

Answer 12

Narrowing of arteries due to atherosclerosis
Deep vein thrombosis (DVT)

Question 13

explain deep vein thrombosis (DVT)

Answer 13

. A DVT is a blood clot that forms in a deep vein most commonly in the leg.

Question 14

Explain the symptoms of atheresclerosis in the legs

Answer 14

The arteries to the legs are most commonly affected and the main symptom is pain in the leg muscles due to limited oxygen supply to the muscle cells and the consequent build-up of lactate and potential cell death.

Question 15

State the role of cholesterol in the body

Answer 15

Cholesterol is a type of lipid that is a component of all cell membranes. It is also a precursor for the synthesis of steroid hormones e.g. testosterone, oestrogen, progesterone.

Question 16

State the source of cholesterol in the body

Answer 16

Cholesterol is synthesised by all cells, although most is produced (25% of total production) in the liver. A diet high in saturated fats or cholesterol will cause an increase in cholesterol levels in the blood.

Question 17

State the different roles of high density lipoproteins (HDL’s) and low density lipoprotein (LDL’s) in the body.

Answer 17

High density lipoproteins (HDL’s) : transport excess cholesterol from the body cells to the liver for elimination. This prevents accumulation of cholesterol in the blood. (Remember : HDL’s = Helpful Delivery to the Liver).

Low density lipoproteins (LDL’s) : transport cholesterol to body cells.

Question 18

Describe the control of cholesterol levels in the body

Answer 18

Most cells have LDL receptors in their cell membrane. These receptors transport LDL into the cell where it releases its cholesterol.

Question 19

What happens once a cell has sufficient cholesterol

Answer 19

Once a cell has sufficient cholesterol, a negative feedback system inhibits the synthesis of new LDL receptors preventing the entry of any more LDL into the cells. Any excess LDL will then circulate in the blood where it may deposit its cholesterol in the arteries forming atheromas.

Question 20

Explain the significance of ratios of HDL to LDL

Answer 20

The ratio of HDL to LDL is important in maintaining good health. A higher ratio of HDL to LDL (more HDL : Less LDL) results in lower blood cholesterol levels and therefore a reduced chance of atherosclerosis.

Question 21

State three ways to maintain a high HDL to LDL ratio

Answer 21

1. Regular physical activity tends to raise HDL levels,
2. Low fat diet - dietary changes aim to reduce the levels of total fat in the diet and to replace saturated with unsaturated fats.
3. Prescribed medications such as statins reduce blood cholesterol by inhibiting the synthesis of cholesterol by liver cells.