Expansion
Sternal, costal and lumbar parts, all converging on the central tendon
Expansion
Three groups of fibres converge on the central tendon:
- Sternal - two small slips from the back of the xiphoid process
- Costal - inner surfaces of the lower six ribs and their costal cartilages
- Lumbar - the right and left crura, and the medial and lateral arcuate ligaments
The right crus arises from the bodies of L1 to L3, the left crus from L1 to L2. The medial arcuate ligament arches over psoas major and the lateral arcuate ligament over quadratus lumborum.
Motor supply is entirely from the phrenic nerve (C3, C4, C5). Sensory supply is phrenic centrally but intercostal peripherally, which is why central diaphragmatic irritation refers to the shoulder tip while peripheral irritation is felt locally in the chest wall.