Final answer:
The portion of the pinna below the external auditory canal is the lobule, which is part of the external ear that includes the pinna and ear canal and serves to conduct sound waves into the middle ear.
Step-by-step explanation:
The portion of the pinna lying inferior to the external auditory canal is the lobule. The pinna, also known as the auricle, is the outer ear structure on the lateral surface of the head that includes the auricle and the ear canal back to the tympanic membrane.
The other parts of the pinna, such as the helix, tragus, and antitragus, play different roles in directing sound waves into the ear canal.
The external ear is the part of the ear that includes the pinna, ear canal, and tympanic membrane, serving to conduct sound waves into the middle ear.
The middle ear contains the three ossicles (malleus, incus, and stapes) which further transmit sound vibrations to the inner ear where they are transduced into neural signals by the cochlea, facilitating the sense of hearing or audition.