Unit 2.7
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What is atherosclerosis?
The accumulation of fatty materials forming an atheroma or plaque beneath the endothelium.
What can the fatty material involved in atheroma consist of?
• Cholesterol • Calcium • Fibrous material
What happens as an atheroma grows?
• Artery thickens • Blockage restricts blood flow due to the decreased diameter of lumen • Restricted blood flow increases blood pressure
What can atherosclerosis cause?
• Angina • Heart attack • Stroke • PVD
What is thrombosis?
When an atheroma ruptures damaging the endothelium, a blood clot may occur (thrombus)
What is the process of thrombosis?
• The atheroma ruptures, damaging the endothelium • Clotting factors cause a cascade of reactions which converts prothrombin to thrombin • Thrombin causes molecules of the plasma protein fibrinogen to form threads of fibrin • Fibrin forms a meshwork that clots blood and seals the wound • This provided a scaffold for scar tissue
Summarise the use of thrombin into fibrin using clotting factors
Prothrombin (active enzyme), using clotting factors and the reactions caused results in thrombin. thrombin causes fibrinogen from plasma protein to form threads of fibrin.
What happens if thrombus beaks loose?
It forms an embolus which can travel through the bloodstream until a blood vessel is blocked.
What can be caused if an embolus blocks a coronary artery and why can tissue death occur?
Heart attack or stroke (if blockage of artery is in the brain). Tissue death can occur due to a lack of oxygen in both cases.
What are peripheral arteries?
All arteries except the brain and heart arteries.
Which arteries are most commonly affected by PVD?
Arteries in the legs.
Why is pain experienced in the muscles of a person with PVD?
Because of the limited supply of oxygen.
What is deep vein thrombosis (DVT)?
A blood clot which forms in a vein usually of the lower leg.
What can DVT do to a pulmonary embolism?
Can break off resulting in a pulmonary embolism in the lungs.
What is cholesterol?
A type of lipid found in the cell membrane.
What is cholesterol synthesised by and where is the main production of cholesterol?
Synthesised by all cells but 25% of production takes place in the liver.
What can cause an increase in cholesterol levels?
A diet high in saturated fats or cholesterol causes.
What transports cholesterol in the bloodstream. Which one is good and which one is bad)
High density and low density (HDL and LDL). HDL is good and LDL is bad.
What does HDL do?
Transports excess cholesterol from the body cells to the liver for elimination, preventing the gathering of cholesterol in blood. It removed cholesterol from inside blood vessels including the coronary artery.
What does LDL do?
Transports cholesterol from the liver to the body and deposits cholesterol inside arteries including coronary arteries. Most cells have LDL receptor that take LDL into the cell where it releases cholesterol.
One cell had a sufficient cholesterol which does what?
It has a negative feedback system which inhibits the synthesis of new LDL receptors.
Why does LDL circulate in the blood?
It may deposit cholesterol in the arteries forming plaque.