Human Anatomy - Kotsan I. Ya. 2009

Muscles and Fascia of the Head
Muscles surrounding the palpebral fissure

The procerus Muscle (m. procerus) originates from the outer surface of the Nasal bone. It inserts into the Skin of the forehead just above the ROOT of the Nose, with some fibers blending into the frontal belly of the occipitofrontalis muscle. Function: pulls the skin of the forehead inferiorly, creating transverse grooves and folds in the glabella region characteristic of a "Mephistophelean" facial expression; acting as an antagonist to the frontal belly of the occipitofrontalis, it helps smooth out transverse wrinkles on the forehead.

Innervation: Facial Nerve.

The orbicularis oculi muscle (m. orbicularis oculi) is elliptical in shape, encircles the entrance to the Orbit, and consists of three parts: orbital, palpebral, and lacrimal.

The orbital part (pars orbitalis) originates from the nasal part of the Frontal bone, the frontal process of the Maxilla, and the medial palpebral ligament. It is divided into two fiber bundles that run along the superior and inferior margins of the orbit, merging near the lateral angle of the eye. The fibers of the frontal belly of the occipitofrontalis and the corrugator supercilii Muscles blend into the superior bundle.

The palpebral part (pars palpebralis) originates from the medial palpebral ligament and the periosteum of the medial orbital wall. It courses across the anterior surface of the superior and inferior tarsal plates toward the lateral angle of the eye, where the fibers from both eyelids interlace to form the lateral palpebral raphe (with some fibers inserting into the periosteum of the lateral orbital wall).

The lacrimal part (pars lacrimalis) originates from the posterior lacrimal crest and the adjacent area of the lateral surface of the Lacrimal bone; it divides into two slips that pass anterior and posterior to the lacrimal sac before blending into the palpebral part of the orbicularis oculi.

Function of the orbicularis oculi: the orbital part narrows the palpebral fissure (squints the eye), pulls the eyebrow inferiorly and the cheek skin superiorly, forming characteristic radiating wrinkles around the outer corner of the eye; the palpebral part closes the eyelids; the lacrimal part dilates the lacrimal sac, thereby regulating tear drainage through the nasolacrimal duct.

Innervation: facial nerve.

The corrugator supercilii muscle (m. corrugator supercilii) lies deep to the superior bundle of the orbital part of the orbicularis oculi. It originates from the medial segment of the supraorbital margin of the frontal bone, extends superolaterally, and inserts into the skin of the forehead above the middle of the eyebrow. Some of its muscle bundles interweave with those of the orbicularis oculi.

Function: pulls the skin of the forehead inferiorly and medially (drawing the eyebrows together), forming vertical folds in the glabella. Frequently, In addition to vertical folds, short transverse wrinkles appear in the middle third of the forehead due to the simultaneous action of the frontal belly of the occipitofrontalis. This eyebrow position occurs during distress or pain and is characteristic of profound emotional suffering.

Innervation: facial nerve.

The depressor supercilii muscle (m. depressor supercilii) is located medial to the corrugator supercilii. It originates from the nasal part of the frontal bone and inserts into the skin of the medial part of the eyebrow. Function: pulls the eyebrow inferiorly.