Principle Skeletal Muscles 1 Muscles of Facial Expression, Muscles that Move the Mandible and Muscles that Move the Eyeballs

Muscles of Facial Expression The muscles of facial expression provide humans with the ability to express a wide variety of emotions. The muscles themselves lie within the layers of superficial fascia. The origins are generally in the fascia or bones of the skull and insertions into the skin of the face

Occipitofrontalis Front and Occipital Bellies Front Belly: Origin – Epicranial Aponeurosis Insertion – Skin superior to orbit Action – Draws scalp forward, raises eyebrows and wrinkles skin of forehead horizontally Occipital Belly Origin – Occipital and Temporal Bones Insertion – Epicranial Aponeurosis Action – Draws scalp backwards

Orbicularis Oris Origin – muscle fibers surrounding opening of mouth Insertion – Skin at corner of mouth Action – Closes and protrudes lips, compresses lips against teeth and shapes lips during speech

Zygomaticus Major Origin – zygomatic bone Insertion – Skin at angle of mouth and orbicularis oris Action – Draws corners of mouth outward and upward as in smiling

Buccinator Origin – Maxilla and Mandible Insertion – Orbicularis Oris Action – presses cheeks against teeth and lips, as in whistling; draws corner of mouth laterally, assists in chewing be keeping food between teeth

Platysma Origin – Fascia over deltoid and pectoralis major muscles Insertion – Mandible, muscles around mouth and skin of lower face Action – Draws outer part of lower lip downward and backward as in pouting; depresses mandible

Orbicularis Oculi Origin – Medial wall of orbit Insertion – Circular path around orbit Action – Closes eye; wrinkles forehead vertically

Levator Palpebrae Superioris Origin – Roof of Orbit Insertion – Skin of upper eyelid Action - Opens Eye

Muscles that Move the Mandible Also known as muscles of mastication because they are used for biting and chewing. These muscles also assist in speech.

Masseter Origin – Maxilla and Zygomatic Arch Insertion – Mandible Action – Elevates and retracts mandible

Temporalis Origin – Temporal Bone Insertion – Mandible Action – Elevates and retracts mandible

Medial Pterigoid Origin – Sphenoid bone and maxilla Insertion – Mandible Action – elevates and protracts mandible and moves mandible from side to side

Lateral Pterygoid Origin – Sphenoid Bone Insertion – TMJ Action – Protracts mandible, depresses mandible and moves mandible from side to side

Muscles that Move the Eyeballs Movement of the eyeballs are controlled by three pairs of extrinsic muscles. These are among the fastest contracting and most precisely controlled skeletal muscles of the body.

Superior Rectus/Inferior Rectus Origin – Tendinous ring attached to bony orbit around the optic foramen Insertion – Superior and central part of the eyeball Action – Moves eyeball upward and medially and rotates its medially Inferior: Origin - Tendinous ring attached to bony orbit around the optic foramen Insertion – Inferior and central part of the eyeball Action – Moves eyeball downward and medially and rotates it laterally

Lateral/Medial Rectus Origin – Tendinous ring attached to bony orbit around the optic foramen Insertion – Lateral Side of Eyeball Action – Moves eyeball laterally Medial: Insertion – Medial Side of Eyeball Action – Moves eyeball medially

Superior/Inferior Oblique Origin – Tendinous ring attached to bony orbit around the optic foramen Insertion – Eyeball between superior and lateral recti Action – moves eyeball downward, laterally and rotates medially Inferior: Origin – Maxilla Insertion – eyeball between inferior and lateral recti Action – moves eyeball upward and laterally and rotates it laterally