The pinna (Latin for feather) is the visible part of the ear that resides outside of the head.

Purpose

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The evolutionary purpose of the pinna is to collect sound. It does so by acting as a funnel, amplifying the sound and directing it to the ear canal. While reflecting from the pinna, sound also goes through a filtering process which adds directional information to the sound (see sound localization, head-related transfer function, pinna notch). The filtering effect of the human pinna preferentially selects sounds in the frequency range of human speech.

Amplification

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Amplification of sound by the pinna, tymphanic membrane and middle ear structures create a sound 20 dB greater than the sound entering the pinna. This amplification is an important factor in inner ear trauma resulting from elevated sound levels.

Anatomy

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The diagram shows the shape and location of these components:

• Anthelix (antihelix) forms a 'Y' shape where the upper parts are:
  • Superior crux (to the left of the fossa triangularis in the diagram)
  • Inferior crux (to the right of the fossa triangularis in the diagram)
• Antitragus is below the tragus
• Auricular sulcus is the depression behind the ear next to the head
• Concha is the hollow next to the ear canal
• Conchal angle is the angle that the back of the concha makes with the side of the head
• Crus of the helix is just above the tragus
• Cymba conchae is the narrowest end of the concha
• External auditory meatus is the opening to the ear canal
• Fossa triangularis
• Helix is the folded over outside edge of the ear
• Incisura anterior (auris) is between the tragus and the antitragus
• Lobe (lobule)
• Scapha
• Tragus

Abnormalities

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There are various visible ear abnormalities:

• Bat ear (also known as wingnut ear) — an ear that sticks out or protrudes
• Cryptotia (hidden ear) — upper auricular sulcus not visible
• Cup deformity — helical rim is compressed
• Darwinian tubercle (auricular tubercle) — a projection from the helical rim
• Lop ear — the top of the helical rim folded over
• Macrotia (also known as big ears, or hypertrophy of the ears)
• Rim kinks — a kink of the helical rim
• Stahl’s bar (also known as Spock ear) — third crus (in between the superior crux and inferior crux) making the top of the ear pointed

See also

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• Earrings for pierced ears

Auditory system

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