Muscle
Diaphragm
Expands the chest by moving downward
High-yield
Motor supply comes from the phrenic nerves, C3–C5. The major passages lie at about T8 for the vena cava, T10 for the esophagus and T12 for the aorta.
Overview
This broad muscle separates the chest from the abdomen. Its fibers converge on a central tendon; during inspiration they draw the domes downward, making more room for the lungs to expand.
Reference facts
- Origin
- Inner xiphoid, lower six ribs and their cartilages, arcuate ligaments and lumbar crura; the right crus usually reaches L3 and the left L2
- Insertion
- Central tendon, which is attached to the fibrous pericardium
- Action
- Lowers the domes to enlarge the thorax during inspiration; also helps raise abdominal pressure
- Innervation
- Right and left phrenic nerves, C3–C5
- Blood supply
- Inferior and superior phrenic arteries, with musculophrenic and pericardiacophrenic contributions
Mnemonic
From above downward, pair vein–food tube–artery with the even levels 8–10–12.
Clinical correlation
An enlarged esophageal hiatus can allow part of the stomach into the chest. A congenital posterolateral defect is a different kind of diaphragmatic hernia and can impair lung development.
Frequently asked questions
What does the diaphragm do?
Lowers the domes to enlarge the thorax during inspiration; also helps raise abdominal pressure.
What nerve innervates the diaphragm?
The diaphragm is innervated by the right and left phrenic nerves, C3–C5.
Where does the diaphragm attach?
Origin: Inner xiphoid, lower six ribs and their cartilages, arcuate ligaments and lumbar crura; the right crus usually reaches L3 and the left L2. Insertion: Central tendon, which is attached to the fibrous pericardium.
What is the blood supply of the diaphragm?
Inferior and superior phrenic arteries, with musculophrenic and pericardiacophrenic contributions.