Which structure is the first to vibrate in response to airborne sound?

• A. Tympanic membrane
• B. Ossicles
• C. Cochlea
• D. Pinna

Answer: (A)

The main idea here is the sequence of how the ear first responds to airborne sound. Sound waves travel through the outer ear and reach the eardrum, causing the tympanic membrane to vibrate. This eardrum is the first structure to convert air pressure fluctuations into mechanical motion, kicking off the entire chain of hearing. The vibrations then move to the ossicles in the middle ear, which amplify and pass the energy to the inner ear via the oval window. The cochlea in the inner ear finally converts those vibrations into neural signals. The pinna mainly helps collect and shape sound for localization and does not serve as the first vibrating transducer in this pathway.