Inferior thoracic aperture

The thoracic outlet is the lower opening of the thoracic cavity whose edges are the lowest ribs.

It is closed by the diaphragm, which separates the thoracic cavity from the abdominal cavity.

The thoracic outlet or inferior thoracic aperture is much larger than the thoracic inlet (superior thoracic aperture).

The thoracic outlet is bounded by:

• The 12th thoracic vertebra posteriorly,
• 11th and 12th pairs of ribs laterally,
• Costal cartilages of ribs 7 through 10 anteriorly, and
• The xiphisternal joint - (i.e.: the articulation between the xiphoid process and the inferior border of the sternal body) anteriorly.

Structures passing through the thoracic outlet between the thorax and abdomen include the inferior vena cava and esophagus, both of which pass through the diaphragm, and the abdominal aorta and thoracic duct which pass through the diaphragm, through the aortic hiatus.