Openings: levels:

• T8 (venous content, inferior vena cava, right phrenic nerve)
• 10 (oesophageal contents, gastric vessels)
• 12 (arterial contents: aorta, v. azygos)

The diaphragm has three arcuate ligaments (medial, lateral and median).

At the end of expiration the diaphragm reaches the fifth rib on the right and the fifth intercostal space on the left.

The diaphragm develops in the neck and hence receives its nerve supply from the cervical spinal cord (C4-C5).

It develops mainly from septum transversum (central tendon) and cervical myotomes (muscular component).

The mesothelial linings are derived from the pleuro-peritoneal membranes (failure of its development leads to Bochdalek's foramen and hernia).

The motor nerve supply arises from the phrenic nerve.

The phrenic nerves pierce the muscular components (not the central tendon) to reach and supply the diaphragm from below.

The sensory nerve (propriozeption) supply is from the lower six intercostal nerves.