The thorax is the center of respiration and circulation in an animal's body. It contains the heart, lungs and associated major blood vessels. In insects, the legs and wings are all attached to the thorax.
In a mammal, the thorax is more commonly referred to as the chest. It has a bony structure protecting the vital internal organs. During respiration, the muscular diaphragm draws air into the thorax by creating a vacuum.
Part of the circulatory system, respiratory system and digestive tract of an insect is housed in its thoraxes. The foregut, similar to a mammalian stomach, is in the insect thorax. The major blood vessel of the insect, similar to the mammalian heart, is also located inside the thorax.