Everything about The Thorax totally explained
The
thorax is a division of an
animal's body that lies between the
head and the
abdomen.
In
mammals, the thorax is the region of the
body formed by the
sternum, the thoracic
vertebrae and the
ribs. It extends from the
neck to the
diaphragm, and doesn't include the
upper limbs. The
heart and the
lungs reside in the
thoracic cavity, as well as many
blood vessels. The inner organs are protected by the
rib cage and the sternum.
In
insects and the extinct
trilobites, the thorax is one of the three main divisions (or
tagmata) of the creature's body, each of which is in turn composed of multiple segments. It is the area where the
wings and legs attach in insects, or an area of multiple articulating plates in trilobites. In most insects, the thorax itself is composed of three segments; the
prothorax, the
mesothorax, and the
metathorax. In extant insects, the prothorax never has wings, though legs are always present in adults; wings (when present) are restricted to at least the mesothorax, and typically also the metathorax, though the wings may be reduced or modified on either or both segments (as in the fly shown, where the metathoracic wings have been reduced to tiny balancing organs called
halteres). In the
Apocritan
Hymenoptera, the first abdominal segment is fused to the metathorax, where it forms a structure known as the
propodeum. Accordingly, in these insects, the functional thorax is composed of four segments, and is therefore typically called the
mesosoma to distinguish it from the "thorax" of other insects.
Each thoracic segment in an insect is further subdivided into various parts, the most significant of which are the dorsal portion (the
notum), the lateral portion (the
pleuron; one on each side), and the ventral portion (the
sternum). In some insects, each of these parts is composed of one to several independent exoskeletal plates with membrane between them (called
sclerites), though in many cases the sclerites are fused to various degrees.
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