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

Structures through the Diaphragm

 * 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