The inferior thoracic aperture is much larger than the superior thoracic aperture. It is closed by the diaphragm, which separates the thoracic and abdominal cavities. The inferior thoracic aperture is bounded by: the 12th thoracic vertebra, 11th and 12th pairs of ribs, costal cartilages of ribs 7 through 10, and the xiphisternal joint - (ie: the articulation between the xiphoid process and the inferior border of the sternal body).

Thorax