Muscular System: Head and Neck Anatomy Study Guide

Vocabulary flashcards covering key terms from the Muscular System: Head and Neck notes.

Sternocleidomastoid (SCM)

Primary neck landmark; origin at the medial clavicle and manubrium; insertion at the mastoid process and superior nuchal line; unilateral contraction tilts the head to the same side and rotates the face to the opposite side; bilateral contraction flexes the neck; innervated by CN XI (accessory nerve).

Trapezius Muscle

Broad, superficial neck muscle; origin external occipital bone and nuchal lines, C1–T12; insertion at the lateral third of the clavicle and scapula; elevates clavicle/scapula (shrug) and supports head; innervated by CN XI and C3–C4 nerves. Clinical note: base for palpation of cervical lymph nodes.（In notes: innervation CN XI, CN III/IV also mentioned.）

Epicranius (Epicranial Muscle)

Muscle with two bellies (frontal and occipital) separated by the epicranial aponeurosis; action: raises eyebrows and scalp; can act independently. Includes frontal belly and occipital belly.

Frontal Belly

Frontal portion of the Epicranius; origin at the epicranial aponeurosis; insertion into the skin of the eyebrows; action: raises eyebrows and wrinkles forehead.

Occipital Belly

Occipital portion of the Epicranius; origin at the occipital bone and mastoid process; insertion at the epicranial aponeurosis; action: raises the scalp.

Epicranial Aponeurosis (Galea Aponeurotica)

Flat, broad tendon linking the frontal and occipital bellies of the Epicranius.

Orbicularis Oculi

Encircles the orbit; three parts (orbital, palpebral, lacrimal); origin at the orbital rim; insertion into the skin at the lateral canthus; action closes the eyelid; when all fibers are active, the eye squints and crow’s feet form at the lateral canthus; innervated by CN VII.

Corrugator Supercilii

Deep to the superior part of the orbicularis oculi; origin at the frontal bone in the supraorbital region; insertion into the skin of the eyebrow; action draws the eyebrow medially and inferiorly toward the nose, creating vertical glabellar and horizontal forehead wrinkles (frowning).

Orbicularis Oris

Complex muscle with four interlacing quadrants around the mouth; originates at the facial modiolus and inserts into the vermilion zone and surrounding skin; actions include pressing lips together, pursing, grimacing, and pouting.

Buccinator

Quadrilateral muscle forming the anterior cheek; origin from the alveolar processes of the maxilla and mandible and the pterygomandibular raphe; inserts toward the lips; action pulls the mouth corner laterally, shortens the cheek, compresses the cheek, helps keep food on occlusal surfaces, and provides suction in infants.

Risorius

Thin muscle often underdeveloped; origin fascia superficial to the masseter; insertion at the ipsilateral labial commissure; action stretches lips laterally to widen the mouth and produces a grimace.

Levator Labii Superioris

Broad muscle elevating the upper lip; origin at the infraorbital rim of the maxilla; insertion into the skin of the upper lip at the ipsilateral commissure.

Levator Labii Superioris Alaeque Nasi (Elvis muscle)

Elevates the upper lip and the ala of the nose, dilating each naris; origin at the frontal process of the maxilla; insertion into the skin of the ala of the nose and upper lip; nickname stems from a sneering/snarling expression.

Zygomaticus Major

Located lateral to Zygomaticus Minor; origin at the zygomatic bone; insertion at the ipsilateral labial commissure; action elevates and pulls the commissure laterally (smiling).

Zygomaticus Minor

Smaller, medial to Zygomaticus Major; origin at the body of the zygomatic bone; insertion into the soft tissue of the upper lip near the levator labii superioris; action elevates the upper lip.

Levator Anguli Oris

Deeper than the zygomaticus muscles; origin at the canine fossa of the maxilla; insertion at the ipsilateral labial commissure; action elevates the commissure.

Depressor Anguli Oris

Triangular muscle in the lower mouth region; origin at the lower border of the mandible; insertion at the ipsilateral labial commissure; action depresses the commissure (frowning).

Depressor Labii Inferioris

Deeper than the depressor anguli oris; origin at the lower border of the mandible; insertion into the skin of the lower lip; action depresses the lower lip, exposing the mandibular incisors.

Mentalis

Short, thick muscle in the chin; origin near the midline of the mandible; insertion into the skin of the chin; action raises the chin, wrinkles the skin, protrudes the lower lip, and can narrow the mandibular vestibule (peach-pit dimpling) and may dislodge lower dentures in edentulous patients.

Platysma

Superficial neck muscle running from the neck to the mouth; origin on skin over the clavicle/shoulder; insertion at the lower border of the mandible and muscles around the mouth; action raises the neck skin and pulls the labial commissures downward (grimacing).

Masseter

Strong, superficial muscle of mastication; origin at the zygomatic arch; insertion at the angle/ramus of the mandible; elevates the mandible; innervated by CN V3 (mandibular division).

Pterygomandibular Raphe

Fibrous band connecting the buccinator and superior pharyngeal constrictor; important landmark for dental anesthesia.

Modiolus

A nodal fibrous point at the labial commissure where several oral muscles meet to stabilize lips.

Vermilion Zone

The red-colored portion of the lips.

Labial Commissure

The corner of the mouth where the upper and lower lips meet.