Which part of the ear is known as the outer ear structure?

The pinna is the correct answer because it is the visible part of the ear that protrudes from the head, shaping the outer ear. Its primary function is to collect sound waves from the environment and funnel them into the ear canal, where the sound is then transmitted further into the inner ear for processing. The structure of the pinna helps in sound localization, allowing us to determine the direction from which a sound originates.

In contrast, the eardrum is a membrane that separates the outer ear from the middle ear and vibrates in response to sound waves, but it does not constitute an outer ear structure itself. The cochlea is located in the inner ear and is responsible for converting sound vibrations into neural signals, playing a crucial role in hearing but not part of the outer ear. Lastly, the ossicles are a chain of small bones found in the middle ear that amplify sound vibrations before they reach the cochlea, further distancing them from the definition of the outer ear.