The posterior auricular muscle is a

muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

behind the auricle of the

outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists of the auricle (also pinna) and the ear canal. It gathers sound energy and focuses it on the eardrum ( tympanic membrane). Structure Auricle T ...

. It arises from the mastoid part of the temporal bone, and inserts into the lower part of the cranial surface of the auricle of the

. It draws the auricle backwards, usually a very slight effect.

Structure

The posterior auricular muscle is found behind the auricle of the

. It consists of two or three fleshy fasciculi. These arise from the

mastoid part The mastoid part of the temporal bone is the posterior (back) part of the temporal bone, one of the bones of the skull. Its rough surface gives attachment to various muscles (via tendons) and it has openings for blood vessels. From its borders, t ...

of the

temporal bone The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears ...

by short aponeurotic fibers. They insert into the lower part of the cranial surface of the auricle of the

. The posterior auricular muscle is supplied by branches of the posterior auricular artery, which continues deep to the muscle. It is drained by the posterior auricular vein that accompanies the artery.

Nerve supply

The posterior auricular muscle is supplied by the

posterior auricular nerve The posterior auricular nerve is a nerve of the head. It is a branch of the facial nerve (CN VII). It communicates with branches from the vagus nerve, the great auricular nerve, and the lesser occipital nerve. Its auricular branch supplies the ...

, a branch of the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of ta ...

(VII).

Function

The posterior auricular nerve draws the auricle of the outer ear backwards. This effect is usually very slight, although some people can wiggle their ears due to a more significant muscle movement.

Postauricular reflex

The postauricular reflex is a

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

myogenic muscle response in humans that acts to pull the ear upward and backward. Research suggests neural circuits for auricle orienting have survived in a vestigial state for over 25 million years. It is often assumed the reflex is a vestigial Preyer reflex (also known as the pinna reflex). A study on auriculomotor activity found that in the presence of sudden, surprising sounds, the muscles around the ear closest to the direction of the sound would respond by moving involuntarily, causing the pinna to perk.

Clinical significance

If the posterior auricular muscle inserts into an unusual part of the auricle of the

, this can cause protruding ears. In one study, the muscle was found to be absent in 5% of people.

References