Auricle

Auricula

Also known as: pinna, helix, antihelix, tragus, concha, lobule, ear lobe

The visible, shell-shaped part of the external ear: a single plate of elastic cartilage covered by tightly adherent skin, except for the cartilage-free lobule.

Overview

The auricle has a characteristic relief of ridges and hollows. The outer rim is the helix, beginning at the crus of the helix above the external meatus; parallel and anterior to it is the antihelix, which divides superiorly into two crura enclosing the triangular fossa; the groove between helix and antihelix is the scapha. The deep hollow next to the meatus is the concha (upper cymba and lower cavum), overlapped in front by the tragus and behind/below by the antitragus, separated by the intertragic notch. The lobule (ear lobe) contains only fibrofatty tissue and is used for piercing and capillary blood sampling.

The cartilage is elastic cartilage, which is continuous with the cartilage of the lateral third of the meatus. The skin is thin and firmly bound to the perichondrium on the lateral surface, and the cartilage depends on the perichondrium for its blood supply. Small vestigial extrinsic (anterior, superior, posterior auricular — facial nerve) and intrinsic muscles are present.

Its complex sensory supply reflects its embryological origin from both the first (V3) and second (VII) arches plus contributions from cervical nerves and the vagus.

Location

Lateral side of the head, around the opening of the external acoustic meatus.

Parts & subdivisions

Helix and crus of helix

Prominent outer rim; Darwin tubercle may be present on its posterosuperior part.

Antihelix, crura and triangular fossa

Curved ridge anterior to the helix; failure of antihelical folding causes "bat ears" (prominent ears).

Scapha

Groove between helix and antihelix.

Concha (cymba and cavum)

Deep bowl leading into the meatus; supplied mainly by the auricular branch of the vagus.

Tragus and antitragus

Small flaps in front of and below the meatal opening; pain on pressing the tragus suggests otitis externa.

Lobule

Soft, cartilage-free lower part.

Anatomy

Innervation

Great auricular nerve (C2–C3) — most of the cranial (medial) surface and the lower lateral surface; lesser occipital (C2) — upper cranial surface; auriculotemporal (V3) — tragus, crus of helix and upper lateral surface; auricular branch of the vagus (Arnold nerve) — concha; facial nerve — small area of concha/posterior surface.

Arterial supply

Posterior auricular artery (from the external carotid) and anterior auricular branches of the superficial temporal artery; small branches of the occipital artery.

Lymphatic drainage

Lateral surface upper half → preauricular (parotid) nodes; cranial surface → mastoid nodes; lobule → superficial cervical nodes.

Histology

Elastic cartilage (chondrocytes in lacunae with abundant elastic fibres in the matrix) surrounded by perichondrium and thin skin with hair follicles, sebaceous and some sweat glands.

Development

Six auricular hillocks appear around the first pharyngeal cleft in week 6: hillocks 1–3 (first arch) form the tragus, crus of helix and part of the helix; hillocks 4–6 (second arch) form the antihelix, antitragus and most of the helix. The auricle starts low on the neck and ascends as the mandible grows.

Clinical significance

Auricular haematoma ("cauliflower ear")

Shearing trauma (rugby, wrestling) collects blood between perichondrium and cartilage, cutting off the cartilage's blood supply; untreated, it necroses and fibroses into a deformed "cauliflower ear". Requires prompt drainage and a pressure dressing.

Congenital anomalies

Preauricular pits/sinuses (incomplete fusion of hillocks) and accessory tags are common; low-set or malformed ears suggest chromosomal (trisomy 13, 18, 21) or arch syndromes (Treacher Collins). Microtia may accompany meatal atresia; renal anomalies should be considered with external ear malformations.

Perichondritis and relapsing polychondritis

Infection (e.g. Pseudomonas after high ear piercing) or autoimmune inflammation of the cartilage — redness and swelling that classically spares the lobule (no cartilage).