INTERNAL STRUCTURE OF THE HUMAN HEART:
The internal structure of the heart consists of four hollow spaces, or chambers, divided by a tissue wall, called the cardiac septum. The flow of blood through the heart is regulated by four valves.
CARDIAC SEPTUM :
A muscular tissue, the cardiac septum, divides the heart into a right and left side. Each side of the heart has an upper chamber or atrium, and a larger, lower chamber, or ventricle. The two sides of the heart have different functions, but they work together to shuttle the blood to all parts of the body.
The right atrium is a thin-walled chamber that receives oxygen-poor, or deoxygenated, blood from the upper and lower parts of the body. It also receives deoxygenated blood from the muscular walls of the heart. The right ventricle fills with the deoxygenated blood from the right atrium and pushes the blood into the pulmonary arteries, which lead into the lungs. The blood is oxygenated in the lungs. The left atrium is also a thin-walled chamber that receives oxygenated blood from the lungs by means of four pulmonary veins. The left ventricle has a very thick muscular wall. When this ventricle contracts, oxygenated blood is forced through the aorta, and its artery branches to all parts of the body.
The heart has four valves that open to let the blood flow when the heart contracts. Each valve has a set of flaps, called cusps or leaflets. The valves allow the blood to flow in only one direction and healthy valves close tightly to stop the blood from flowing backwards. A stethoscope can detect the sound of the heart valves opening and closing. The tricuspid valve is located between the right atrium and the right ventricle and the pulmonary valve on the right ventricle regulates the opening to the pulmonary artery. The mitral valve is situated between the left atrium and the left ventricle, while the aortic valve on the left ventricle controls the opening to the aorta.
The rate at which the heart beats is controlled by electrical impulses mediated by the involuntary, or autonomic, nervous system. One nerve, coming from the brain, speeds up the heart beat, while another slows it down. The nerves