Diaphragm

It is a thin musculotendinous structure that fills the inferior thoracic aperture. It separates the thoracic cavity from the abdominal cavity and it is dome-shaped.

Positions

It is attached peripherally to:

• Xiphoid process
• Costal margins of the thoracic wall
• Ends of the 11th and 12th ribs
• Ligaments that go across posterior abdominal wall
• Vertebrae of Lumbar region

The pericardium is attached to the central tendon, where fibres converge.

Structures through the Diaphragm

Diaphragm scheme.

• Aortic hiatus - Aorta
• Oesophageal hiatus - oesophagus, vagus nerve, azygous and hemi-azygous vein
• IVC foramen - Inferior Vena Cava through central tendon

Innervation

Motor innervation

• Phrenic nerve

Sensory innervation

• Intercostal nerves (ribs 6-12)
• L1 and L2 roots
• Phrenic nerve

Function

For inspiration and raising intra-abdominal pressure

Mechanism of Breathing

Inspiration

1. Intercostal muscles contract
2. Ribs elevate transversely and anteriorly
3. Diaphragm contracts and flattens
4. Thorax volume increases, decreasing pressure
5. Air goes in

Expiration

1. Intercostal muscles and diaphragm relax
2. Thorax volume decreases, increasing pressure
3. Air is forced out

Links

Bibliography

SNELL, Richard S. Clinical Anatomy by Regions. 8th Edition edition. 2004. ISBN 978-0-7817-6404-9.