Expansion
Septum transversum, pleuroperitoneal membranes, dorsal mesentery of the oesophagus, and body wall
Expansion
- Septum transversum - becomes the central tendon
- Pleuroperitoneal membranes - close the pericardioperitoneal canals
- Dorsal mesentery of the oesophagus - becomes the crura
- Body wall (somatic mesoderm) - the peripheral muscular rim
The nerve supply records this history. The septum transversum forms opposite the C3, C4 and C5 somites in the neck and then descends, dragging the phrenic nerve with it, which is why a structure in the abdomen is innervated from the cervical spinal cord, and why diaphragmatic irritation refers pain to the shoulder tip.