||The external ear consists of the pinna, the external auditory canal and the outermost layer of the tympanic membrane.
The pinna (Latin for feather) or external auricle (from the Latin auricula, the diminutive of auris, ear) is a convoluted and flattened funnel-shaped appendage whose shape is determined by the underlying flexible elastic auricular cartilage. The auricular cartilage is contiguous with the cartilage of the outer portion of the external auditory canal.
In the human, the pinna plays only a rudimentary function in the amplification and localization of sound, whereas in lower mammals such as the bat and the dog this function is highly developed. In addition to its auditory function, the folds and convolutions of the pinna provide some protection by shielding the external canal from direct trauma.
As the pinna is attached to the side of the head in a relatively exposed position, it is subject both to local trauma and to the immediate and delayed effects of solar radiation.
The pinna is formed in the embryo by the coalescence of six tiny hillocks or tubercles, located on the dorsal end of the first (mandibular) and second (hyoid) branchial arches. There is a wide variation in the size and shape of the normal auricle, and minor developmental abnormalities are often found.
A severe congenital malformation of the pinna may, however, be associated with an abnormality of the middle or inner ear, and should alert the examiner to the possibility of an underlying hearing loss. Although most congenital malformations are genetic in origin, exposure of the fetus to drugs or infection can result in an abnormality in the position or shape of the pinna.