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Frontalis Muscle

You must have seen patients with drooping upper lids who lift their eyebrows to provide a tiny bit more upper eyelid elevation. The frontalis muscle lifts the brows and is a weak retractor of the upper eyelids. The frontalis muscle is a part of the occipitofrontalis musculofascial complex (frontalis muscle, galea aponeurotica, and occipitalis muscle) of the scalp. This broad band of tissue extends across the top of the skull from the occiput to the eyebrows. The A in the mnemonic for remembering the layers of the “SCALP” is this aponeurosis (S, scalp, C, subcutaneous tissue, A, aponeurosis, L, loose areolar tissue, P, periosteum.)

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The fibrous aponeurosis becomes the frontalis muscle inferior to the hairline. Contraction of the frontalis muscle causes the horizontal furrows in the forehead. You may notice that the forehead furrows do not extend to the temporal hairline. The frontalis muscle thins laterally and does not extend to the tail of the brow. The lack of frontalis pull over the tail of the brow explains the temporal brow ptosis seen so commonly in older adults.

Like the other muscles of facial expression, the frontalis muscle is innervated by a branch of the facial nerve. Unlike with other branches of the facial nerve, there is no redundancy in the innervation of the frontalis muscle. A single branch, the frontal nerve, innervates the frontalis muscle. The path of the frontal nerve can be estimated by drawing a line from the tragus of the ear to the point 1 cm above the tail of the eyebrow. You will learn to take special care to avoid damage to the frontal nerve during any surgery near the path of the frontal branch. Damage to the nerve may leave the patient with a permanent paresis or paralysis of the frontalis muscle, resulting in a brow ptosis.

Development

Mesoderm of second pharyngeal arch.

Origin

It has no bony origin. It arises from the orbicularis oculi, skin and subcutaneous tissue of the eyebrow.

Insertion

Galea aponeurotica.

Nerve supply

Temporal branch of facial nerve.

Action

It produces transverse wrinkles on the forehead. Thus, this muscle causes the sign of exclamation. It helps to the move the scalp. It opposes the action of orbicularis oculi

Clinical Relevance

An active trigger point in the frontalis muscle belly is identified by flat palpation as spot tenderness above the medial end of the eyebrow. An active trigger point in the occipitalis muscle belly lies in a small hollow just above the superior nuchal line approximately 4 cm (1.5 inch) lateral to the midline. Spot tenderness is located by flat palpation.

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Frontalis Muscle


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By | 2018-02-19T11:55:17+00:00 July 24th, 2017|Anatomy, Head and Neck, Muscles|0 Comments