Thorax

Diagram of a tsetse fly, showing the head, thorax and abdomen
Diagram of a tsetse fly, showing the head, thorax and abdomen

The thorax is a division of an animal's body that lies between the head and the abdomen.

In humans, the thorax is the region of the body that extends from the neck to the diaphragm, not including the upper limbs. The heart and the lungs reside in the thoracic cavity, as well as many blood vessels. This area is protected by the rib cage and the sternum.

In insects and the extinct trilobites, the thorax is one of the three main segments of the creature's body. It is the area where the wings and legs attach in insects, or an area of multiple articulating plates in trilobites.

The trilobite body is divided into three major sections, a cephalon with eyes, mouthparts and sensory organs such as antennae, a thorax of multiple similar segments (that in some species allowed enrollment), and a pygidium, or tail section. © Sam Gon III
The trilobite body is divided into three major sections, a cephalon with eyes, mouthparts and sensory organs such as antennae, a thorax of multiple similar segments (that in some species allowed enrollment), and a pygidium, or tail section.
© Sam Gon III


Thorax is also the name of a character in Brooke McEldowney's comic strip, 9 Chickweed Lane, who has also made guest appearances in McEldowney's other strip, Pibgorn. Apparently a large, amiable elderly farmer, he is... not quite human, and has a quantum anomaly in his shed.