Bones of the Thorax

Sternum

  • jugular notch (1)
  • facet for head of first rib
  • manubrium (2)
  • facet for head of second rib
  • manubriosternal joint (sternal angle) (3)
  • body (made up of several fused sternabrae) (4)
  • xiphoid process (5)

A Typical Rib

    A typical rib has the following characteristics:
  • head -- articulates with bodies of vertebrae
  • neck
  • tubercle -- articulates with transverse processes
  • angle -- a point just lateral to the
    tubercle where the shaft bends forward;
  • costal groove -- lodges intercostal vessels and nerves
typical rib

First Rib

The first rib is atypical. It is found to be short, flat and more sharply curved than any of the others. It has upper and lower surfaces, with outer and inner borders, and on its head there is one articular facet only.

The upper surface has two grooves for the subclavian artery and subclavian vein, separated by the scalene tubercle for the attachment of the scalene anterior muscle.

This rib has very little movement during respiration and serves as a base attachment for the intercostal muscles and the ribs below. In other words, during respiration, the muscles in the first intercostal space contract, drawing up on the rib below, which in turn allows its muscles to pull up on the rib below it and so forth, until all ribs have moved through a small distance. The combined movements increase the transverse and anteroposterior diameters of the thoracic cavity.

first rib

Thoracic Vertebrae

There are 12 thoracic vertebrae. The 1st and 12th are called atypical and the rest are typical. All of the typical vertebrae have the same characteristics. The 1st and 12th vertebrae have slightly different characteristics than the typical ones. What are the characteristics of a typical thoracic vertebra?

Characteristics of a typical thoracic vertebra include:
  • body (1)
  • superior and inferior demifacets (2,3)
  • pedicle (4)
  • superior and inferior articular processes (5, 6)
  • transverse process (with an articular process) (7,10)
  • lamina (8)
  • spinous process (9)
  • superior and inferior notches (13,12)
  • vertebral canal(14)
  • not a bone but an integral part of the vertebral column is the intervertebral disk (11)

Thoracic Cavity

Transverse section
through the thorax.
cross section through thorax
When you examine the thorax in cross section, you will notice that it is kidney shaped in form. You can also appreciate the anterior, posterior and lateral boundaries. We will refer to this view of the thorax as we continue.

After taking a look at the bones of the thorax, it is now time to examine the thoracic wall as a whole. The thoracic wall is made up of the sternum, ribs plus three layers of intercostal muscles, diaphragm and the intercostal vessels and nerves. Remember that the function of the thorax is respiration (exchanging oxygen for carbon dioxide). The structures of the thoracic wall are designed to do just that.

Bony Boundaries of Thorax Muscles of the Thorax


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