Diaphragm

Musculus diaphragma

A musculotendinous dome-shaped partition separating the thoracic and abdominal cavities. It has sternal, costal, and lumbar origins converging on the central tendon. Three major openings transmit the aorta (T12), esophagus (T10), and inferior vena cava (T8).

Type Muscle
Système corporel Muscular
Région corporelle Thorax
Structure parente thoracic segment muscle
Nom latin Musculus diaphragma
FMA ID 13295

Fonction

The primary muscle of respiration. Contraction flattens the dome-shaped muscle, increasing thoracic volume and creating negative pressure to draw air into the lungs during inspiration.

Signification clinique

Diaphragmatic hernias allow abdominal organs to enter the thoracic cavity. Phrenic nerve paralysis causes diaphragmatic elevation. Hiccups result from involuntary diaphragmatic spasms.

Questions fréquentes

How does the diaphragm produce breathing?
During inhalation, the diaphragm contracts and flattens its dome-shaped resting configuration, descending toward the abdomen. This increases the vertical dimension of the thoracic cavity, reducing intrathoracic pressure below atmospheric pressure and causing air to rush into the lungs. During exhalation at rest, the diaphragm relaxes and passively returns to its dome shape, reducing thoracic volume and expelling air.
What nerve controls the diaphragm and where does it originate?
The diaphragm is controlled almost entirely by the phrenic nerve, which originates from cervical spinal cord levels C3, C4, and C5—remembered by the mnemonic 'C3, 4, and 5 keep the diaphragm alive.' Each hemidiaphragm receives its own phrenic nerve, one from each side. This is why a high cervical spinal cord injury (above C3) results in loss of spontaneous breathing.
What is a diaphragmatic hernia?
A diaphragmatic hernia occurs when abdominal organs—such as the stomach, intestines, or spleen—herniate through a defect in the diaphragm into the thoracic cavity. Congenital diaphragmatic hernias are a serious neonatal emergency causing lung compression and respiratory failure. Acquired hernias can occur through the esophageal hiatus (hiatal hernia) or from traumatic rupture.
What causes hiccups, and are they related to the diaphragm?
Hiccups result from involuntary, repetitive spasms of the diaphragm. Each spasm causes a sudden inhalation that is abruptly stopped by closure of the vocal cords, producing the characteristic 'hic' sound. Common triggers include rapid eating, carbonated drinks, alcohol, and gastric distension. Persistent hiccups lasting more than 48 hours may indicate an underlying medical condition.
What three major structures pass through the diaphragm, and at what vertebral levels?
Three major structures pass through openings in the diaphragm: the inferior vena cava passes through at the T8 level (caval opening), the esophagus passes through at T10 (esophageal hiatus), and the aorta passes through at T12 (aortic hiatus). A common mnemonic is 'I ate (8) ten (10) eggs (esophagus) at (aorta) twelve (12).'

Structures associées

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Educational Disclaimer

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Data sources: Terminologia Anatomica, Foundational Model of Anatomy, Wikidata.