The heart

• The function of the heart is to pump blood around the body
• In mammals the heart is part of a double circulatory system
• Blood moves around the body due to the pressure difference between the pressure in the heart (high) and the pressure in the blood vessels(low)
• Deoxygenated blood returns from the body in the vena cava(vein)
• The atria-ventricular valve separate the atrium and the ventricle
• The semi-lunar valve is between the ventricle and either the aorta or the pulmonary artery
• blood enters the left atrium via the pulmonary vein
• The heart has four chambers
• The heart is made out of cardiac muscle
• Systole means the contraction of heart muscles
• Diastole means the relaxation of the heart muscles
• The Atrio-ventricular valves and semi-lunar valves ensure that blood only flows in one direction (prevents the back flow of blood)
• Atrio-ventricular valves open when the pressure in the atria increases above the pressure in the ventricle.
• Semi-lunar valves open when the pressure in the ventricle increases above the pressure in the aorta
• The atria-ventricular valves are the tricuspid and bicuspid valves
• Valves only open one way due to tendons that anchor the valve (heart strings)
• Cardiac output = stroke volume x Heart Rate
• The two most common causes of blockage to the coronary artery (coronary heart disease) are Atherosclerosis and Thrombosis
• Thrombosis is the clotting of blood within a vessel
• Atherosclerosis is the process of atheroma formation
• Atheroma is when the Luman of the artery is narrowed due to a build up of fatty deposits and cholesterol underneath the endothelium of the artery
• The atheroma may cause reduced blood flow to heart muscle cells beyond that point
• If the blood vessel is blocked completely the muscle cells in the heart will get no oxygen causing a heart attack (myocardial infarction)
• Thrombosis is when plaque may rupture and trigger blood clotting over a damaged area this build up quickly causing the blockage of the artery
• An aneurysm is when the artery becomes blocked the blood pressure builds up in front of the blockage pressing on the artery was causing a bulge outwards
• Risk factors of Coronary Heart Disease are high cholesterol diet, high lipid diet, lack of exercise, smoking and stress
• The coronary arteries provide the cardiac muscle in the heart with oxygenated blood.
• Cardiac output = Stroke Volume x Heart Rate
• Cardiac output is the volume of blood expelled from the heart from the left ventricle in one minute
• Stroke volume is the volume of blood expelled from the left ventricle in one pump
• Stroke Volume is the volume of blood expelled from the left ventricle in one heart beat
• Heart rate is the number of cardiac cycles per minute