Central tendon

The central tendon is a strong aponeurotic structure located at the centre of the diaphragm. It forms the non-muscular part of the diaphragm and serves as the central attachment point for its muscle fibres.

Attachments

The central tendon receives fibres from all three muscular parts of the diaphragm, including:

• Sternal part

• Costal part

• Lumbar part

Superiorly, the fibrous pericardium is firmly attached to the upper surface of the central tendon, with the heart resting directly upon it.

Openings of the central tendon

The caval foramen is located within the right leaflet of the central tendon at vertebral level T8. Structures passing through this opening include:

• Inferior vena cava (IVC)

• Terminal branches of the right phrenic nerve

• Lymphatic vessels

Other openings of the diaphragm

The oesophageal hiatus lies within the muscular part of the diaphragm at the vertebral level T10. It transmits:

• Oesophagus

• Anterior and posterior vagal trunks

The aortic hiatus is located posterior to the diaphragm (between the crura) at the vertebral level T12. Structures passing through it include:

• Descending aorta

• Thoracic duct

• Azygos and hemiazygos veins

Nerve Supply

Although the central tendon itself is nonmuscular, the diaphragm is innervated by:

• Phrenic nerves (C3C5) providing motor supply

• Lower intercostal nerves contributing to peripheral sensory supply

Blood Supply

The diaphragm receives arterial blood supply from:

• Pericardiacophrenic arteries

• Musculophrenic arteries

• Inferior phrenic arteries

Functions

The central tendon serves as the insertion point for diaphragmatic muscle fibres. During inspiration, diaphragmatic contraction pulls the central tendon inferiorly, increasing thoracic volume and facilitating lung expansion. In addition, the caval foramen widens during inspiration, promoting venous return through the inferior vena cava.