Circulatory or Cardiovascular System : delivers oxygen, nutrients, and hormones to the various body tissues and transports waste products to the appropriate waste removal systems. Three major parts of the system: the heart, blood vessels and blood HEART: - pericardium: double-walled membrane surrounding the heart - epicardium: external layer of the heart - myocardium: middle and thickest layer of the heart; the actual heart muscle - endocardium: inner layer of the heart; lines the heart chambers and valves

Arteries that serve the heart are known as coronary arteries, because they resemble a crown. The coronary veins remove waste products from the myocardium. Coronary veins remove waste products from the myocardium. Artery: blood vessel that carries oxygenated blood away from the heart. Vein: returns blood to the heart and away from the areas of the body Capillaries: single-celled vessels that connect the arteries and veins. The slower rate of travel of the blood through the capillaries allows time for diffusion of oxygen, nutrients, and waste products.

The heart is divided into right and left sides. These sides are then divided into chambers. Mammals and aviaries have 4- chambered hearts. Reptiles have 3 chambers. All vessels entering the heart enter through the atrium. Ventricles are the pumping chambers of the heart, and all vessels leave the heart here. The narrow tip of the heart is called the apex. The left and right atria are separated by the septum. Blood flow through the heart is controlled by valves. Right atrioventricular valve (right AV valve): this valve controls the opening between the right atrium and the right ventricle. Also called the tricuspid valve because it has three points.

Pulmonary semilunar valve (pulmonary valve): located between the right ventricle and pulmonary artery and controls the blood entering the lungs. This valve is shaped like a half-moon. Left atrioventricular valve (left AV valve): controls the opening between the left atrium and the left ventricle. Also called the bicuspid because it has to points. Aortic semilunar valve (aortic valve): located between the left ventricle and aorta. Controls blood entering the arteries. Also half-mooned shape.

BLOOD FLOW THROUGH THE HEART 1)The right atrium receives blood from all tissues (except the lungs). Blood flows from the right atrium through the tricuspid valve into the right ventricle. 2)The right ventricle pumps blood through the pulmonary semilunar valve and into the pulmonary artery, which carries it to the lungs. 3)The left atrium receives oxygenated blood from the lungs through the four pulmonary veins. The blood flows through the mitral valve into the left ventricle.

1)The left ventricle receives blood form the left atrium. From the left ventricle, blood goes out through the aortic semilunar valve into the aorta and is pumped to all parts of the body (except the lungs). 2)Blood is returned to the right atrium, and the cycle continues. and-medicine/the-heart/v/meet-the-heart and-medicine/the-heart/v/flow-through-the-heart

Heartbeat: rate and regularity of the heart rhythm. Alternating sequence of relaxation and contraction of the heart chambers. heart/v/lub-dub heart/v/circulatory-system-and-the-heart