Physiology And Health - Heart Flashcards
What is atherosclerosis?
The accumulation of fatty material consisting mainly of cholesterol, fibrous material and calcium, forming an atheroma or plaque. It is the root cause of various cardiovascular diseases including angina, heart attack, stroke and peripheral vascular disorders.
Where does an atheroma form?
Beneath the endothelium (inner lining) of the artery wall.
What does an atheroma do?
As an atheroma grows, the artery thickens and loses its elasticity. It also reduces the diameter of the lumen of the artery which restricts blood flow, resulting in increase blood pressure.
What happens if an atheroma ruptures?
The damage to the endothelium causes the release of clotting factors. Clotting factors cause the enzyme prothrombin to be converted into its active form, thrombin.
What is thrombin?
Thrombin causes molecules of the soluble plasma protein fibrinogen to form threads if insoluble fibrin protein.
What do fibrin threads do?
Form a mesh work that platelets adhere to, forming a blood clot which seals a wound and provides a scaffold for the formation of scar tissue.
What is thrombosis?
The formation of a blood clot (thrombus) in a vessel.
What happens if a thrombus breaks loose?
It forms an embolus that travels through the bloodstream until it blocks a blood vessel.
What can thrombosis in a coronary artery cause?
A myocardial infarction (MI)
What can thrombosis in an artery in the brain cause?
A stroke
What does thrombosis result in?
The death of some tissue served by the blocked artery as the cells are deprived of oxygen.
What do peripheral vascular disorders cause?
Narrowing of the arteries due to atherosclerosis of arteries other than those of the heart or brain
What can blood clots result in?
Deep vein thrombosis (DVT) and pulmonary embolism.
What is DVT?
The formation of a blood clot in a deep vein most commonly in the lower part of the leg. In DVT pain is experienced in the leg muscles due to a limited supply of oxygen.
How is a pulmonary embolism caused?
By a part of a thrombus breaking free and travelling through the bloodstream to the pulmonary artery where it can cause blockage resulting in chest pain and breathing difficulties.
What is cholesterol?
A component of cell membranes and a precursor for steroid synthesis. Most cholesterol is synthesised by the liver from saturated fats in the diet.
What are lipoproteins?
They contain lipid and protein.
What does High-density lipoprotein (HDL) do?
Transports excess cholesterol from the body cells to the liver for elimination and so prevents the accumulation of cholesterol in the blood.
What does low- density lipoprotein (LDL) do?
Transports cholesterol to body cells.
What are LDL receptors?
Most cells have these and they take LDL into the cell where it releases cholesterol.
Describe how blood circulates?
Blood circulates from the heart through the arteries to the capillaries to the veins and back to the heart.
What happens when blood moves away from the heart?
There is a drop in blood pressure.
What is the central lumen lined by?
The endothelium which is surrounded by layers of tissue.
What do arteries do?
Carry blood away from the heart.
What do arteries consist of?
An outer layer of connective tissue containing elastic fibres and a middle layer containing smooth muscle with more elastic fibres.
What do the arteries do to accommodate the blood surging out the heart?
Stretch and recoil to accommodate the sure of blood after each heart contraction.
What are arterioles?
Small arteries
What can the arterioles do and what does this process allow?
Contract or relax causing vasoconstriction or vasodilation to control blood flow. This process allows changing demands of the body’s tissues to be met.
What happens to the arterioles during strenuous exercise?
The arterioles leading to working muscles vasodilate increasing blood flow and the arterioles leading to abdominal organs vasocontract reducing blood flow.
What are venules?
Small veins
How is blood transported from arterioles to venules?
By passing through a dense network of capillaries.
What do capillaries allow?
The exchange of substances with tissues.
How thick are capillaries?
One cell thick so they allow quick and efficient exchange of materials.
What do veins do?
Carry blood towards the heart
What do veins have?
An outer layer of connective tissue containing elastic fibres. They have a much thinner muscular wall than arteries.
What can we say about the blood pressure in veins?
Blood flows along veins at lower pressure than arteries.
What can we say about the lumen of the vein?
It is wider than that if an artery
What are the function of valves?
They prevent the back flow of blood.
What do coronary arteries do?
Supply oxygenated blood to the heart muscle.
What does the carotid artery do?
Supplies oxygenated blood to the brain
What does the renal artery do?
Supplies oxygenated blood to the kidneys