heart
The heart is a major organ in the higher animal circulatory system. The main function is to provide pressure to run the blood to various parts of the body. The human heart is located in the middle of the chest left, the volume is about the equivalent of a fist size, weighing about 350 grams. Women's hearts are usually smaller and lighter than men's. The heart of the cavity and then divided into the atrium and ventricle, the atrium from the vein back to the heart, the ventricle will drive into the arteries. Mammals and birds have two heart and two ventricles; reptiles also have two atrium and two ventricles, but the two ventricles are not completely separated; amphibians have two atrium and a ventricle; fish is only a heart and a ventricle. ...