Which structure is the tube that runs from the outer ear to the middle ear at the eardrum, typically about 35 mm long?

• A. Tympanic Membrane
• B. Semicircular Ducts
• C. Auditory Canal
• D. Cochlea

Answer: (C)

The structure is the external auditory canal, also called the ear canal. It forms the passage from the outside of the head to the eardrum and is about 35 mm long. Its skin-lined tube, with hair and ceruminous glands, helps protect the middle ear and aids in guiding sound toward the tympanic membrane, which is the eardrum. The semicircular ducts are part of the balance system in the inner ear, and the cochlea is the hearing organ inside the inner ear—neither is a tube from the outer ear to the eardrum.