Heart

• Valves are flaps of tissue that open when pressure increases behind them and close when pressure decreases
• The heart is divided into four chambers, two atria (right and left) and two ventricles (right and left)
• Atriums are thin-walled chambers that receive blood from veins and pump it into ventricles
• Deoxygenated blood is received by the right side of the heart from the body and oxygenated blood is pumped by the left side of the heart to the body.
• The septum is a thick muscular wall that divides the right and left sides of the heart.
• Blood flows from the right side to the left side of the heart through the pulmonary valve and tricuspid valve
• Atrial systole occurs first, followed by ventricular systole
• The pulmonary semilunar valve separates the right ventricle from the pulmonary artery, while the aortic semilunar valve separates the left ventricle from the aorta.
• The tricuspid valve separates the right atrium from the right ventricle
• The tricuspid valve separates the right atrium from the right ventricle, while the bicuspid or mitral valve separates the left atrium from the left ventricle.
• Coronary circulation occurs during diastole, or relaxation phase of the cardiac cycle
• Ventricular systole pushes blood out of the heart
• Diastolic pressure is lower than systolic pressure
• The atria contract simultaneously during atrial systole, which lasts about 0.1 seconds.
• Ventricular systole begins with contraction of the papillary muscles, causing the cusps of the mitral and tricuspid valves to close tightly against their respective annuli.