Outlet of Thorax | Diaphragm Large Openings | Inferior Aperture of thorax | Piercing structures

The video introduces the inferior aperture of the thoracic cavity, or the outlet of the thorax. This outlet is larger than the inlet and is closed off by the diaphragm, a large musculo-tendinous partition. The diaphragm possesses a central tendon, right and left crura, and associated ligaments like the median, medial, and lateral arcuate ligaments.

The boundaries of the thoracic outlet are defined: anteriorly by the infrasternal angle (formed by the xiphoid process and the costal margin), posteriorly by the 12th thoracic vertebra, and laterally by the lower ribs and their costal margins.

The diaphragm has several important openings. The vena caval opening is found in the central tendon at the level of T8. It is quadrilateral and allows passage of the inferior vena cava, right phrenic nerve, and lymphatics of the liver. This opening dilates when the diaphragm contracts.

The esophageal opening is at the level of T10, is elliptical, and transmits the esophagus, vagal trunks, and left gastric vessels. This opening constricts when the diaphragm contracts.

The aortic opening is located behind the median arcuate ligament at the level of T12. It allows passage of the descending aorta, thoracic duct, and azygos vein. This opening does not change in size during diaphragm contraction.

In addition to the major openings, there are smaller ones, including the space of Larry, which transmits the superior epigastric artery. An enlarged space of Larry is known as the foramen of Morgagni. Other small openings include those for the musculophrenic artery, intercostal vessels and nerves, sympathetic trunks, splanchnic nerves, and phrenic nerves.