Overview

The diaphragm is the body's main breathing muscle — a large, dome-shaped sheet of muscle that separates the chest from the abdomen. It sits at the bottom of the ribcage and does the majority of the work with every breath.

When it contracts, it flattens and pulls air into the lungs; when it relaxes, air flows out.

Location and Connections

Domes across the bottom of the ribcage, separating the chest (thorax) from the abdomen
Attaches to the lower ribs, breastbone and spine
Its central tendon is where the muscle fibres converge
The phrenic nerves (from the neck) supply it — the only way the brain tells it to contract

What It Does

The diaphragm drives quiet breathing, assists forceful breathing during exercise, and helps with coughing, sneezing and clearing the airway. It also supports pressure changes in the abdomen that matter for posture, lifting and circulation.

Common Problems

Diaphragm fatigue — a heavy, aching sensation with hard exercise or breathlessness
Pain near the bottom of the ribcage with deep breathing, which can also come from the ribs, muscles or abdominal organs
A stitch — a sharp, cramping pain in the side during exercise, often linked to breathing and ribcage muscles
Shortness of breath — which needs assessment, especially if sudden or worsening

Breathing difficulty, wheezing, chest tightness or pain that spreads beyond the chest should not be assumed to be the diaphragm — get urgent medical assessment.

Clinical Relevance

Deep-breathing exercises are a core part of recovery from rib and chest injuries, because the diaphragm and intercostals must keep working even when the chest hurts. Persistent shortness of breath, sudden breathing difficulty, or chest pain with exertion deserves prompt assessment.

References

StatPearls. "Anatomy, Thorax: Diaphragm." https://www.ncbi.nlm.nih.gov/books/NBK519558/

Diaphragm Anatomy