Which dome-shaped muscle under the lungs helps us breathe?

• A. Bronchi
• B. Alveoli
• C. Pleura
• D. Diaphragm

Answer: (D)

The diaphragm is the dome-shaped muscle that sits just below the lungs and forms the floor of the thoracic cavity. When it contracts, it flattens and moves downward, increasing the chest cavity’s vertical height and creating negative pressure to draw air into the lungs. When it relaxes, it curves back up, helping push air out as you exhale. The other options aren’t muscles involved in breathing: bronchi are air passages, alveoli are tiny sacs for gas exchange, and pleura are membranes around the lungs. The diaphragm’s movement is the primary driver of inhalation and exhalation.