Auricle

The auricle (or pinna) is the elastic cartilaginous part of the external ear which projects outwards from the side of the head and is covered over by skin. The auricle is connected inwards to the external acoustic meatus or canal that leads to the tympanic membrane.

The cartilaginous framework of the auricle molds to create various patterns of elevations and depressions. The outside elevated rim is called the helix, which runs parallel to a smaller inner rim called the antihelix. Both cartilaginous rims give ear its concave geometry. Superiorly, there is a shallow depression between helix and antihelix, called the scaphoid fossa.

The central hollow part of the auricle is called the concha, which serves as the starting point of the external acoustic meatus. Just anterior to the concha–above the opening of external acoustic meatus–there is an elevation called the tragus.

The only part of the auricle which does not have a cartilage inside it, is called the lobule, that is situated inferiorly. Opposite to the tragus, just above the lobule, there is another elevation called the antitragus.

There are numerous intrinsic and extrinsic muscles associated with the auricle. The intrinsic muscles are located within the cartilaginous framework of the auricle and contribute towards changing its shape. Whereas, the extrinsic muscles have an outside origin–from the skull or the scalp–and contribute towards repositioning the auricle towards the sound waves.

The auricle receives its sensory innervation from numerous sources including auriculotemporal, greater auricular and lesser occipital nerves. The deeper part, such as the concha, receives its innervation from the vagus nerve. Motor innervation to auricular muscles comes from the facial nerve.

The blood supply to auricle arrives via branches of external carotid artery, including the superficial temporal (anteriorly), posterior auricular and occipital arteries (posteriorly). The veins accompany the arteries. Lymphatics from auricle drain into parotid (anteriorly), mastoid (posteriorly) and possibly upper deep cervical lymph nodes.