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Human Body Study

Diaphragm

The dome-shaped sheet of muscle beneath the lungs — the main engine of breathing.

The respiratory tract From the upper airway down through larynx, trachea and bronchial branching into the two lungs, with the diaphragm at the base. A separate inset shows alveoli — the microscopic gas-exchange sacs inside the lungs. Each label links to the article for that part. Alveoli Upper respiratory tract Larynx Trachea Bronchi Lungs Diaphragm The respiratory tract — schematic, not to scale.

What it does

Section titled “What it does”
  • Inhalation — the diaphragm contracts and flattens, enlarging the chest cavity and drawing air in.
  • Exhalation — it relaxes back into its dome, the chest recoils, and air is pushed out.
  • Assisted by the rib muscles, especially during heavy breathing.

Key idea

Section titled “Key idea”

Breathing works by changing the chest’s volume, not by the lungs pulling on air — and the diaphragm is what changes that volume. It runs automatically but can also be consciously controlled.