The Heart

• Multicellular organisms require transport systems to supply their cells and remove waste products.
• In humans, one of the functions of the circulatory system is to transport substances.
• The circulatory system includes the heart, blood vessels, and white blood cells.
• Development of cardiovascular disease can be evaluated through taking pulses and calculating blood flows.
• The heart is a muscular organ that pumps blood around the body.
• The heart has four chambers: two atria and two ventricles.
• Blood enters the heart through the atria.
• Blood from two vena cavae enters the right atrium.
• Blood from the pulmonary veins enters the left atrium.
• Blood is prevented from flowing back into the atria by heart valves.
• Blood leaves the heart in the body's main artery, the aorta, from the left side, and the pulmonary artery, from the right.
• Humans have a double circulatory system.
• The heart pumps blood through two circuits: the pulmonary circulation and the systemic circulation.
• The pulmonary circulation is the part of the circulatory system that involves the right side of the heart, the lungs, and the blood vessels that connect them together.
• The systemic circulation transports oxygen and nutrients to the body, and carbon dioxide and other wastes away from cells.
• In a healthy person, this lower pressure is optimum for the diffusion of gases.
• The pulmonary circulation transports blood to the lungs.
• The pulmonary circulation is under lower pressure because blood is delivered to the lungs only, which are very close to the heart.
• The systemic circulation includes the left side of the heart, the rest of the body apart from the lungs, and the blood vessels that connect them together.
• Part of the blood is being delivered to the body, while the remainder of the blood is being transported to the lungs, meaning that oxygen can be picked up from the lungs, while at the same time, blood is also being delivered to the body.
• The blood becomes oxygenated when carbon dioxide diffuses from the blood into the lungs.
• At the lungs, oxygen diffuses into the blood from the alveoli.
• The systemic circulation is under high pressure because it has to deliver blood to the extremities of the body.
• Circulating blood passes through the heart twice in one complete circulation of the body.
• The atria and ventricles of the heart contract in unison, and when full, the ventricles also contract in unison.
• Deoxygenated blood from the body enters the right atrium.