Posterior auricular muscle

The posterior auricular muscle, located posterior to the auricle, plays a role in repositioning the ear. It originates from the mastoid process of the temporal bone, with insertion at the root of the posterior auricle.

Summary

• origin: mastoid process

• insertion: posterior auricle root

• blood Supply: posterior auricular artery

• innervation: posterior auricular branch of the facial nerve (CN VII)

• action: draws the auricle backwards

Gross anatomy

Origin

As part of the extrinsic muscles of the auricle, the posterior auricular muscle originates from the mastoid part of the temporal bone and consists of two or three fleshy fasciculi.

Insertion

The muscle inserts into the lower section of the cranial surface of the auricle of the outer ear, serving to anchor the muscle's function in positioning the ear.

Arterial supply

Blood supply to the muscle is facilitated by the posterior auricular artery, a branch of the external carotid artery.

Venous drainage

Venous drainage of the external ear is primarily mediated by the pterygoid plexus, external jugular vein, and maxillary veins, with anterior and posterior courses draining into the mastoid and parotid gland nodes, respectively.

Innervation

The innervation of the posterior auricular muscle is provided by the posterior auricular nerve, an extracranial branch of the facial nerve (CN VII).

Action

The primary action of the posterior auricular muscle is to pull the ear backward, aiding in the positioning of the auricle of the outer ear relative to the skull.

Clinical significance

The postauricular reflex represents a vestigial muscle response in humans, functioning to pull the ear upwards and backwards. Research suggests the neural circuits for auricle orienting have remained in a vestigial state for over 25 million years ⁵. Some people exhibit a more significant muscle movement, allowing them to wiggle their ears ⁶.

In the presence of sudden, surprising sounds, the muscles around the ear closest to the sound direction may respond involuntarily. This reflex movement results in the pinna being pulled backwards and flattening, demonstrating auriculomotor activity ⁷.