Dictionary Definition
thorax
Noun
1 the middle region of the body of an arthropod
between the head and the abdomen
2 the part of the human body between the neck and
the diaphragm or the corresponding part in other vertebrates [syn:
chest, pectus]
3 part of an insect's body that bears the wings
and legs [also: thoraces (pl)]
User Contributed Dictionary
English
Etymology
From sc=Grek, from sc=Linb.Noun
thorax (plural thoraces or thoraxes)Derived terms
Translations
region of the mammalian body
- Czech: hruď, hrudník
- Greek: θώρακας
Extensive Definition
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 does not 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.