Higher Human Biology Unit 2 Physiology & Health KEY AREA 7: Pathology of Cardiovascular Disease (CVD)

Higher Human Biology We are going to build on the knowledge and skills that you developed during N5 and will learn about the following Physiology & Health key areas : - Key Area 1 – Reproductive Organs Key Area 2 –Hormonal Control of Reproduction Key Area 3 – Biology of Controlling Fertility Key Area 4 – Ante- and Postnatal Screening Key Area 5 – Structure and Function of Arteries, Capillaries and Veins Key Area 6 – Structure and Function of the heart Key Area 7 – Pathology of Cardiovascular Disease (CVD) Key Area 8 – Blood Glucose Levels and Obesity

Physiology & Health Learning Intentions KEY AREA 7– Pathology of Cardio Vascular Disease (CVD) a)Process of Atherosclerosis b)Thrombosis c)Causes of Peripheral Vascular Disorders d)Control of Cholesterol levels and familial hypercholesterolemia

7a) Atherosclerosis Atherosclerosis is the formation of plaques called atheromas under the endothelium in the wall of an artery Initially plaques are formed of fatty materials (consisting mainly of cholesterol), but as years increase, the plaques become enlarged as fibrous material, calcium and more cholesterol are added - making larger atheromas Large atheromas lead to:- Decreased diameter of the artery’s lumen Restriction of blood flow to the capillary bed An increase in blood pressure Hardening of the arteries (artery walls lose elasticity due to deposits of calcium) Various Cardiovascular diseases e.g. Coronary Heart Disease (including angina) Strokes Heart Attacks (myocardial infarctions) Peripheral vascular disease

7b) Blood Clotting Blood clotting is a protective device to prevent loss of blood at a wound e.g. when Atheroma's rupture they damage the endothelium cells. The presence of damaged cells leads to the release of blood clotting factors that change the inactive enzyme prothrombin into its active form thrombin Thrombin Fibrinogen Threads of fibrin (a soluble plasma protein)  (an insoluble protein) Fibrin threads a meshwork that clots the blood, seals the wound and provides a scaffold for the formation of scar tissue The formation of a blood clot (thrombus) is called thrombosis

7c) Thrombosis Atheromas on the inside lining of an artery can damage the endothelium leading to the formation of a thrombus. If the thrombus breaks loose, it is called an embolus An embolus is carried along by blood until it blocks a narrow vessel and restricts or blocks block flow If an embolus blocks a coronary artery, it’s called coronary thrombosis, and the heart muscle can be starved of oxygen and may lead to myocardial infarction (heart attack) A thrombus that causes a blockage in an artery to the brain may lead to a stoke

7d) Causes of peripheral vascular disorders The peripheral arteries are those other than the aorta, coronary and carotid arteries Peripheral vascular disease is the narrowing of the arteries(other than those of the heart and brain) due to atherosclerosis Peripheral vascular disease mostly affects leg arteries. Blood flow to the legs is restricted and pain is felt due to lack of oxygen Deep Vein Thrombosis (DVT) is the formation of a thrombus (blood clot) in a vein (most commonly in the lower leg). This causes the area to be painful, swell up and veins close to the skin surface can become engorged with blood. If an embolus blocks a pulmonary artery it leads to the serious situation called a pulmonary embolism and the person experiences chest pains, breathing difficulties and palpitations

7e) Cholesterol levels Lipids are a diverse group of organic compounds which include simple lipids (e.g. fats) and more complex lipids (e.g. steroids) Cholesterol is important because it is needed for the synthesis of steroids (e.g. sex hormones) and is a basic component of cell membranes The presence of cholesterol at a specific concentration in the bloodstream is essential to the health and well-being of the human body Cholesterol is produced in the liver cells from saturated fats present in a normal balanced diet Lipoproteins are molecules containing a combination of lipid and protein, and are found in blood plasma which transports the lipids from one part of the body to another

7f) Low-density Lipoproteins (LDL) Low-density lipoproteins (LDL) are produced by the liver Most body cells synthesise LDL receptors which then embed in their cell membrane. When a molecule of LDL carrying LDL-cholesterol becomes attached to the receptor, the cell engulfs the LDL-cholesterol and the cholesterol is released for use by the cell When the body cell contains an adequate supply of cholesterol, a negative feedback system is triggered which inhibits the synthesis of new LDL receptors. Therefore less LDL-cholesterol in the blood is absorbed by body cells. Some of the excess cholesterol is taken up by endothelial cells lining the inside of an artery, and is deposited in an atheroma. This will happen to people that eat a diet rich in saturated fats, and/or suffer from hypercholesterolemia (see later slides)

7g) Control of cholesterol levels

7h) Excess Cholesterol Some of the excess cholesterol is taken up by endothelial cells lining the inside of an artery, and is deposited in an atheroma. This will happen to people that:- Eat a diet rich in saturated fats and/or Suffer from Hypercholesterolemia (see later slides)

7i) High-density lipoproteins (HDL) Some of the excess cholesterol is transported by High-density lipoproteins (HDL) from body cells to the liver for elimination – which prevents a high level of cholesterol accumulating in the bloodstream Also, HDL-cholesterol is not taken into artery walls so does not contribute to atherosclerosis The healthy balance of HDL-cholesterol and LDL-cholesterol molecules is essential to ensure excess cholesterol is not in the bloodstream Normally, HDL molecules carries about 30% of blood cholesterol, and LDL molecules carry about 70%. If there is a higher ratio of HDL to LDL, there will be a decrease in blood cholesterol, thus decreasing the chances of atherosclerosis and CVD

7j) Familial Hypercholesterolemia (FH) Familial hypercholesterolemia (FH) is an inherited disorder that shows an autosomal dominant gene that predisposes individuals to developing high levels of cholesterol. In FH sufferers the mutated gene causes a decrease in the number of LDL receptors present in the cell membranes, or a change in their structure that renders then non-functional. FH sufferers have a VERY high-LDL-cholesterol levels If left untreated, FH sufferers will have CV problems at a much younger age than others in the population People whose family has a history of FH can take a genetic test to determine if they have inherited an FH allele FH can be treated by modifying life style choices and taking drugs such as statins

7k) Statins Regular exercise causes people to have higher concentrations of HDL- cholesterol Low fat diets cause people to have higher concentration of HDL-cholesterol Drugs called Statins lower cholesterol in the blood by inhibiting the enzyme essential for the synthesis of cholesterol by liver cells

Physiology & Health Questions KEY AREA 7 – Pathology of CVD 1.Testing Your Knowledge 1Page 186 Q’s Quick Quiz