Anatomy · Muscles

Frontalis

The muscle that raises the eyebrows

Scalp and forehead · frontal belly of occipitofrontalis

A thin, quadrilateral sheet of muscle under the skin of the forehead that has no bony attachment of its own. It runs from the skin of the eyebrows up to the galea aponeurotica, the tough sheet over the top of the skull, where it joins the occipital belly to form occipitofrontalis. It raises the eyebrows and wrinkles the forehead, as in surprise, and is supplied by the facial nerve.

How to spot them

▸A sheet on the forehead attached to the skin of the eyebrows below and the galea aponeurotica above, without any bone attachment
▸The frontal belly of occipitofrontalis, joined to the occipital belly at the back of the head by the galea
▸Supplied by the temporal branch of the facial nerve
▸Its contraction wrinkles the forehead horizontally

What to know

The forehead muscle that raises the eyebrows and produces horizontal creases in the skin of the brow

Frontalis — the frontal belly of occipitofrontalis.

It is joined to a muscle at the back of the head by a tough sheet over the top of the skull

Frontalis — the galea aponeurotica links it to the occipital belly.

A stroke that damages the motor cortex on one side may leave the forehead moving normally, whereas damage to the facial nerve itself paralyses it

Frontalis — forehead sparing in an upper motor neurone facial palsy, because its motor neurones receive input from both hemispheres.

Botulinum toxin is injected into it to smooth the horizontal lines on the brow

Frontalis — cosmetic treatment of forehead lines.

A loose layer under the sheet over the skull lets the scalp be torn off in one piece in a scalping injury

Frontalis — the galea and the loose areolar tissue beneath it (the L of SCALP).

A person with a drooping upper eyelid can be helped by a sling that borrows it to lift the lid

Frontalis — the frontalis sling operation for ptosis.

Its motor supply is the temporal branch of the seventh cranial nerve

Frontalis — the temporal branch of the facial nerve.

Key ideas

Because the upper face is served by both cerebral hemispheres, a stroke on one side spares the forehead, but a lesion of the nerve itself (as in Bell's palsy) gives a smooth, flat forehead: the standard way to tell upper from lower motor neurone facial weakness.
It has no bony origin, so it acts through the skin and the galea rather than a bone, moving the brow rather than a joint.

Quick-fire facts

•Origin: the epicranial aponeurosis (galea aponeurotica)
•Insertion: the skin of the eyebrows and the muscles of the forehead (procerus, corrugator supercilii, orbicularis oculi)
•Action: raises the eyebrows, wrinkles the forehead and, acting from the eyebrows, pulls the scalp forwards
•Nerve supply: the temporal branch of the facial nerve
•Blood supply: supraorbital, supratrochlear and superficial temporal arteries
•The occipital belly arises from the superior nuchal line, is supplied by the posterior auricular branch of the facial nerve, and pulls the scalp back
•The frontal and occipital bellies together, with the galea aponeurotica, form the epicranius
•The layers of the scalp form the mnemonic SCALP: skin, connective tissue, aponeurosis (galea), loose areolar tissue, pericranium
•Forehead wrinkles are perpendicular to the direction of its fibres, which run vertically

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Sources

Kenhub — Frontalis muscle