Mechanics of Inhalation During Breathing

Steps:

• Identify inhalation process: Diaphragm contracts and flattens to increase chest volume.
• Note external intercostal role: These muscles contract to elevate ribs, expanding the rib cage.
• Confirm rib movement: Rising ribs further enlarge thoracic cavity for air intake.
• Match to options: Select the choice aligning all three actions with inhalation.

Why C is correct:

• During inhalation, the diaphragm flattens via contraction (per respiratory physiology), external intercostals contract to lift ribs, increasing lung volume by Boyle's law (pressure decreases as volume increases).

Why the others are wrong:

• A: Dome-shaped diaphragm and falling ribs indicate exhalation, not inhalation.
• B: Dome-shaped diaphragm signals relaxation during exhalation; rising ribs contradict muscle relaxation.
• D: Relaxed external intercostals and falling ribs describe exhalation, not inhalation.

Final answer: C