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Anatomy & Physiology: Muscle Actions

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  • Frontalis

    Raises the eyebrow.

  • Procerus

    Lowers the eyebrow.

  • Nasalis

    Flares the nostrils.

  • Orbicularis oculi

    Closes the eyelid.

  • Zygomaticus major

    Produces a smile.

  • Orbicularis oris

    Puckers the lips.

  • Buccinator

    Compresses the cheeks.

  • Platysma

    Depresses the corner of the mouth.

  • Temporalis

    Closes and elevates the mandible (jaw).

  • Masseter

    Closes and elevates the mandible (jaw).

  • Lateral Rectus (Eye Muscle)

    Abducts the eye (moves it laterally).

  • Superior Oblique (Eye Muscle)

    Moves the eye down and out (inferior and lateral).

  • Superior Rectus (Eye Muscle)

    Moves the eye upward.

  • Inferior Rectus (Eye Muscle)

    Moves the eye downward.

  • Medial Rectus (Eye Muscle)

    Moves the eye medially (toward the nose).

  • Inferior Oblique (Eye Muscle)

    Moves the eye superiorly and laterally (up and out).

  • Sternocleidomastoid (SCM) Bilateral Action

    Flexes the neck.

  • Sternocleidomastoid (SCM) Unilateral Action

    Rotates the face to the opposite side.

  • External Intercostals

    Elevate the ribs during inspiration.

  • Internal Intercostals

    Depress the ribs during forced expiration.

  • Diaphragm

    Primary muscle of inspiration.

  • Rectus Abdominis

    Flexes the vertebral column.

  • External Oblique

    Rotates the trunk to the opposite side.

  • Internal Oblique

    Rotates the trunk to the same side.

  • Transversus Abdominis

    Compresses the abdomen.

  • Splenius (Deep Back Muscle)

    Extends the head.

  • Erector Spinae

    Extends the vertebral column.

  • Transversospinalis

    Extends and rotates the spine.

  • Quadratus Lumborum

    Performs lateral flexion of the vertebral column.

  • External Urethral Sphincter

    Closes the urethra.

  • External Anal Sphincter

    Closes the anus.