The Heart - 9.2

• Atria (single: atrium) are the thin-walled chambers at the top of the heart that receive blood.
• Ventricles are the thick-walled chambers at the bottom of the heart that pump out blood.
• Septum is the structure that separates the right and left sides of heart and the oxygenated and deoxygenated blood.
• Pulmonary veins are the veins that carry oxygenated blood from the lungs to the left atrium of the heart.
• Venae Cavae (singular: vena cava) are the large veins that bring deoxygenated blood to the right atrium.
• Aorta is the largest artery in the body and it takes oxygenated blood from the left ventricle and delivers it to the rest of the body.
• Pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
• Deoxygenated blood comes into the right atrium thru the vena cava (from body and head) and oxygenated blood comes into the left atrium thru the pulmonary veins (from lungs).
• Then, blood flows from atria into the ventricles which pump blood out of heart by contracting strongly, producing a large force that squeezes inwards on blood in heart and pushes it out.
• Blood in left ventricle is pumped into aorta (to take to body and head) and blood in right ventricle is pumped into pulmonary artery (to take back to lungs).
• Atrioventricular valves are between the atria and ventricles and allow blood to flow from atria to ventricles but prevent it from going in the opposite direction.
• Semilunar valves (means half moon, refers to their shape) are near the openings of the aorta and pulmonary artery which allow blood to flow from ventricles into arteries but prevent the blood backflow from arteries to ventricles.
• Atria simply receive blood but ventricles pump it around the body. Ventricles have much thicker, muscular walls than the atria. Especially the left ventricle, which pumps blood to rest of the body. Right ventricle pumps to lungs, which is close to heart. Blood flowing to lungs in pulmonary artery has lower blood pressure than blood flowing to body in aorta.
• Coronary arteries deliver oxygenated blood to the heart muscle. The heart is so thick that nutrients and oxygen in the heart wouldn't diffuse around the muscle quickly enough so coronary arteries supply these nutrients and oxygen so the heart can undergo aerobic respiration and release energy that the muscle uses to contract.
• Coronary arteries can get blocked by cholesterol deposits which build up in walls of arteries. These deposits make the artery wall stiff and the lumen of the artery narrow, so it's difficult for blood to flow which can form blood clots. So, the heart doesn't get oxygen, its cells can't respire aerobically, and can't contract so the heart stops beating.
• Coronary heart disease (CHD) is a disease caused by the blockage of the coronary arteries.
• To prevent CHD, don't smoke, eat healthy, and exercise regularly. Reduce saturated fats in ur diet by substituting animal fats with plant oils when cooking. Fast food contains lots of animal fats, so reduce that. Exercise prevents extra weight gain, keeps u fit and decreases blood pressure.
• Pulse rate is the number of times an artery expands and recoils in one minute; it's a measure of heart rate.
• Electrocardiograph (ECG) is a graph showing the electrical activity of the heart plotted against time.
• The valve on the left side of the heart is made of two parts and is called the bicuspid or mitral valve. The valve on the right side of the heart is made of three parts and is called the tricuspid valve.
• Muscles in the heart relax and blood flows in.

  Semilunar valves shut to prevent blood from flowing into the ventricle.

  Atrioventricular valves open and muscles of atria relax to allow blood flow into the heart from veins.
• Atria muscles contract, muscles of ventricles remain relaxed and blood is forced from atria into ventricles.

  Valves in the veins are forced shut by the pressure of blood to stop blood from flowing back into the veins.

  Semilunar valves remain shut.
• Muscles in the walls of the ventricles contract to force blood out of the ventricles into the arteries.

  Semilunar valves are forced open by the pressure of the blood.

  Atrioventricular valves are forced shut by the pressure of the blood.