Muscles Review: Head and Neck Anatomy

Muscles of Mastication - CN V, V3

Overview: These muscles are primarily responsible for the movements of the mandible and are innervated by the third division of the Trigeminal nerve ( $V_3$ ).
Masseter
- Action: Elevates the mandible.
- Origin:
  - Zygomatic arch.
- Insertion:
  - Superficial head: Lateral surface of the mandible.
  - Deep head: Lateral surface of the ramus.
- Innervation: Masseteric nerve of CN V, $V_3$ .
Temporalis
- Action: Elevates and retracts the mandible.
- Origin: Temporal fossa.
- Insertion: Coronoid process.
- Innervation: Deep temporal nerves of CN V, $V_3$ .
Medial Pterygoid
- Action: Elevates, protrudes, and provides side-to-side movement of the mandible.
- Origin:
  - Deep head: Medial surface of the lateral pterygoid plate.
  - Superficial head: Maxillary tuberosity and pyramidal process of the palatine bone.
- Insertion: Medial surface of the angle of the mandible and the ramus.
- Innervation: Medial pterygoid nerve of CN V, $V_3$ .
Lateral Pterygoid
- Action: Protrudes, opens, and provides side-to-side movement of the mandible.
- Origin:
  - Superior head: Greater wing of the sphenoid bone.
  - Inferior head: Lateral surface of the lateral pterygoid plate.
- Insertion: Neck of the condyle at the pterygoid fovea.
- Innervation: Lateral pterygoid nerve of CN V, $V_3$ .

Muscles of Facial Expression - CN VII

Overview: Grouped by region; all are innervated by the Facial nerve (CN VII).
Scalp and Forehead
- Frontalis
  - Action: Raises eyebrows and wrinkles the forehead.
  - Origin: Epicranial aponeurosis.
  - Insertion: Skin of the eyebrow and the root of the nose.
- Occipitalis
  - Action: Pulls the scalp back.
  - Origin: Superior nuchal line and mastoid process.
  - Insertion: Epicranial aponeurosis.
- Note: The Frontalis and Occipitalis are connected together by the epicranial aponeurosis.
Eyes
- Orbicularis oculi
  - Action: Closes the eyelids (blinking, squinting).
  - Origin: Orbital rim, nasal process of the frontal bone, and frontal process of the maxilla.
  - Insertion: Skin at the lateral canthus or serves to completely encircle the eye.
- Corrugator supercilia
  - Action: Draws eyebrows medially and down (associated with frowning).
  - Origin: Supraorbital region of the frontal bone.
  - Insertion: Skin of the eyebrow.
Oral Region
- Orbicularis oris
  - Action: Closes and puckers the lips (kissing, blowing).
  - Origin: Facial modiolus.
  - Insertion: Skin of the lips at the labial commissures and the ridges of the philtrum.
- Buccinator
  - Common Names: Known as the "trumpet muscle"; essential for nursing in infants.
  - Action: Keeps food pushed back on masticatory surfaces; aids in sucking, whistling, and chewing.
  - Origin: Alveolar process of the maxilla and mandible, and the pterygomandibular raphe.
  - Insertion: Pulls the commissure laterally; compresses the cheeks.
- Risorius
  - Action: Draws corners of the mouth laterally (associated with grimacing).
  - Origin: Fascia superficial to the masseter.
  - Insertion: Skin at the ipsilateral labial commissure at the facial modiolus.
- Levator Labii Superioris
  - Action: Elevates the upper lip.
  - Origin: Infraorbital rim.
  - Insertion: Skin of the upper lip within the ipsilateral labial commissure at the facial modiolus.
- Levator Labii Superioris Alaeque Nasi
  - Common Names: Known as the "Elvis muscle."
  - Action: Elevates the upper lip and the ala of the nose; facilitates snarling.
  - Origin: Frontal process of the maxilla.
  - Insertion: Skin of the ala of the nose and the upper lip.
- Zygomaticus Major
  - Action: Elevates the labial commissure and pulls it laterally when smiling.
  - Origin: Zygomatic bone (lateral to the zygomaticus minor).
  - Insertion: Skin at the ipsilateral labial commissure at the facial modiolus, and in/around the orbicularis oris.
- Zygomaticus Minor
  - Action: Elevates the upper lip; assists in smiling.
  - Origin: Body of the zygomatic bone (medial to the zygomaticus major).
  - Insertion: Skin of the upper lip.
- Levator Anguli Oris
  - Action: Elevates the labial commissure when smiling.
  - Origin: Canine fossa.
  - Insertion: Skin at the ipsilateral labial commissure at the facial modiolus.
- Depressor Anguli Oris
  - Action: Depresses the angle of the mouth when frowning.
  - Origin: Inferior border of the mandible.
  - Insertion: Ipsilateral labial commissure at the facial modiolus.
- Depressor Labii Inferioris
  - Action: Depresses the lower lip, exposing the incisors.
  - Origin: Inferior border of the mandible.
  - Insertion: Skin of the lower lip.
- Mentalis
  - Action: Raises the chin, wrinkling the skin and causing lower lip protrusion; narrows the mandibular vestibule.
  - Origin: Anterior mandible near the midline.
  - Insertion: Skin of the chin.

Muscles of the Neck

Platysma
- Action: Raises the skin of the neck and pulls the labial commissures down.
- Origin: Skin superficial to the clavicle and the shoulder.
- Insertion: Inferior border of the mandible.

Hyoid Muscles

Suprahyoid Muscles
- General Action: Assist in mastication and swallowing.
- Digastric
  - Action: Elevates the hyoid and depresses the mandible.
  - Origin:
    - Anterior belly: Intermediate tendon.
    - Posterior belly: Mastoid notch.
  - Insertion:
    - Anterior belly: Digastric fossa.
    - Posterior belly: Intermediate tendon.
  - Innervation:
    - Anterior belly: Mylohyoid nerve of CN V, $V_3$ .
    - Posterior belly: Posterior digastric nerve of CN VII.
- Mylohyoid
  - Action: Elevates the hyoid, depresses the mandible, and forms the floor of the mouth.
  - Origin: Mylohyoid line on the medial surface of the mandible.
  - Insertion: Body of the hyoid.
  - Innervation: Mylohyoid nerve of CN V, $V_3$ .
- Stylohyoid
  - Action: Elevates and retracts the hyoid.
  - Origin: Styloid process.
  - Insertion: Body of the hyoid.
  - Innervation: Styloid nerve of CN VII.
- Geniohyoid
  - Action: Elevates and protrudes the hyoid or depresses the mandible.
  - Origin: Genial tubercles.
  - Insertion: Body of the hyoid.
  - Innervation: CN XII (Hypoglossal nerve).
Infrahyoid Muscles
- Omohyoid
  - Action: Depresses the muscles of the hyoid.
  - Origin: Scapula.
  - Insertion: Body of the hyoid.
- Sternohyoid
  - Action: Depresses the hyoid.
  - Origin: Sternum.
  - Insertion: Body of the hyoid.
- Sternothyroid
  - Action: Depresses the thyroid and larynx; notably, it does not depress the hyoid directly.
  - Origin: Sternum.
  - Insertion: Thyroid cartilage.
- Thyrohyoid
  - Action: Depresses the hyoid; raises the thyroid and larynx.
  - Origin: Thyroid.
  - Insertion: Greater cornu of the hyoid.

Tongue Muscles

Extrinsic Tongue Muscles
- Function: Move the tongue; all innervated by the Hypoglossal nerve (CN XII).
- Genioglossus
  - Action: Protrudes the tongue and depresses the center.
  - Origin: Genial tubercles.
  - Insertion: Base of the tongue near the apex and the hyoid bone.
- Styloglossus
  - Action: Retracts and elevates the tongue.
  - Origin: Styloid process.
  - Insertion: Lateral surface of the tongue, apex, and the border of the body and base.
- Hyoglossus
  - Action: Depresses and retracts the tongue.
  - Origin: Greater cornu and body of the hyoid.
  - Insertion: Lateral surface and body of the tongue.
Intrinsic Tongue Muscles
- Function: Shape the tongue; these muscles have no distinct bony origins or insertions and are all innervated by the Hypoglossal nerve (CN XII).
- Superior longitudinal
  - Action: Shortens the tongue and curls the tip upward.
  - Location: Dorsal surface running anterior to posterior.
- Inferior longitudinal
  - Action: Shortens the tongue and curls the tip downward.
  - Location: Ventral side of the tongue running anterior to posterior.
- Transverse
  - Action: Narrows and elongates the tongue.
  - Location: Side to side.
- Vertical
  - Action: Flattens and broadens the tongue.
  - Location: Dorsal to ventral surface.

Muscles of the Pharynx

Stylopharyngeus
- Action: Elevates and widens the pharynx.
- Origin: Styloid process.
- Insertion: Pharyngeal walls.
- Innervation: Glossopharyngeal nerve (CN IX).
Pharyngeal Constrictor Muscles
- Action: Raise the pharynx and larynx during swallowing.
- Origins:
  - Superior: Hamulus, mandible, and pterygomandibular raphe.
  - Middle: Hyoid bone and stylohyoid ligament.
  - Inferior: Thyroid and cricoid cartilage.
- Insertion: Medial pharyngeal raphe in the pharynx.
- Innervation: Vagus Nerve (CN X).

Muscles of the Soft Palate and Uvula

Palatoglossus
- Action: Elevates the posterior tongue; aids in swallowing.
- Origin: Palatine aponeurosis of the soft palate.
- Insertion: Side of the tongue.
- Innervation: Vagus nerve (CN X).
Palatopharyngeus
- Action: Closes off the nasopharynx during swallowing by moving the palate.
- Origin: Soft palate.
- Insertion: Laryngopharynx and thyroid.
- Innervation: Vagus nerve (CN X).
Levator Veli palatini
- Action: Raises the soft palate to close the nasopharynx during speech and swallowing.
- Origin: Inferior surface of the temporal bone.
- Insertion: Median palatine raphe.
- Innervation: Vagus nerve (CN X).
Tensor Veli palatini
- Action: Tenses and lowers the soft palate.
- Origin: Auditory tube and the inferior surface of the sphenoid.
- Insertion: Median palatine raphe.
- Innervation: Medial pterygoid nerve (CN V, $V_3$ ).
Muscles of the Uvula
- Action: Shortens and broadens the uvula, thereby changing the contour of the soft palate.
- Note: These muscles lie entirely within the uvula structure.