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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 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. 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.

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 them to roll up into a ball), and a pygidium, or tail section.



References

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Study guide

Up to date as of January 14, 2010

From Wikiversity

The thorax is the area of the body bounded by the ribcage, or bony thorax, and lies between the head and abdomen.

In mammals, the thorax is the region of the body formed by the sternum anteriormedially, the thoracic vertebrae posteriormedially, the ribs laterally and the diaphragm inferiorly. It extends from the neck to the diaphragm, and does not include the upper limbs, which are considered to be another region. 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.

It contains three potential spaces lined by mesothelium; the paired plural cavities, which surround the lungs, and the pericardium, which surrounds the heart.

Contents of the thorax

Viscera

Bones

  • Sternum- manubrium, sternum and xiphoid process
  • Ribs and costal cartilages
  • Thoracic vertebrae T1-12


Muscles

Anterior

  • Pectoralis major
  • Pectoralis minor

Posterior

  • Subclavius
  • Serratus anterior
  • Levator scapulae
  • Trapezius
  • Latissimus dorsi
  • Rhomboids- major and minor

Vasculature

  • Superior vena cava
  • Inferior vena cava
  • Aorta, including ascending and descending aorta and the aortic arch
  • Pulmonary artery
  • Azygos vein

Surface antatomy

  • Nipples

The Mediastinum

The mediastinum [1] consists of all the structures lying inside the bony cavity, and is surrounded by loose conncective tissue. The mediastinum can by divided into superior and inferior mediastinum by the Plane of Louis, and imaginary line drawn between the sternal angle and the intervertebral disc between T4 and T5 vertebrae.

The inferior mediastinum can be further divided into:

  • Anterior mediastinum, which lies between the posterior aspect of the sternum to the anterior pericardium
  • Middle mediastinum, which contains the pericardium and, more importantly, the heart
  • Posterior mediastinum, which lies from behind the pericardium to the anterior face of the spine.

Reference


1911 encyclopedia

Up to date as of January 14, 2010
(Redirected to Database error article)

From LoveToKnow 1911

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Simple English

[[File:|thumb|In this insect diagram, the thorax is labelled B.]]

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

In mammals, the parts that make up the thorax are the sternum, the thoracic vertebrae and the ribs. It starts from the neck and stop at the diaphragm.

In insects and crustaceans, it is the middle of the three main body sections. The walking legs are usually located on the thorax.


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