Describing the structure of the heart and its functions.
The circulatory system is also known as the cardiovascular system. Cardio- refers to the heart and vascular refers to a channel or vessel through which blood flows. This system consists of heart, the blood and the blood vessels.
All other body systems depend on the circulatory system for nourishment and oxygen and for removal of wastes. The circulatory system acts as a transport system that takes care of the needs of all the other system.
The Heart. Your heart is just as big as your fist. It is located in the thoracic cavity just behind the breastbone and between the lungs. Your heart beats day and night without stopping and will continue to do so for as long as you live.
The heart wall. The heart is a hollow muscular organ. Its wall encloses four chambers. The whole heart is enclosed in a sac called pericardium.
Interior of the heart. The interior of the heart has a left side and right side separated by a thick, muscular wall called septum. Each side has an upper chamber called atrium and a lower chamber called ventricle. The atria (plural of atrium) are smaller than the ventricles, and their walls are thinner. Their job is to hold the blood before it goes down the ventricles. The ventricles are bigger and have thicker muscular walls. Their job is to pump blood. The right ventricle pumps blood to the lungs, while the left ventricle pumps blood to all parts of the body. For this reason, the left ventricle has a thicker muscular wall.
Blood moves through the heart in just one direction. This is made possible by one-way valves found between the atria and ventricles and the blood vessels attached to them. The valve between the left atrium and the left ventricle is the bicuspid valve, while the one between the right atrium and the right ventricle is the tricuspid valve. The valve between the left ventricle and the aorta is the aortic semilunar valve, and the one between the right ventricle and the pulmonary artery is the pulmonary semilunar valve. All the heart valves prevent blood from flowing backwards.
Functions of the heart. The heart is the pump that enables blood to circulate around the body. The automatic and rhythmic contraction of its muscles enables the body to meet its needs. A healthy heart contracts about 75 times a minute or 4500 times an hour. The heart is an efficient machine that generates its own power for as long as it is supplied with nutrients and energy.