The Face: Muscles of Mastication and Facial Expression

Comprehensive review practice flashcards covering the anatomy of the face, muscles of mastication and facial expression, pharyngeal arch derivatives, cranial nerve innervations, mandibular biomechanics, the midface buttress system, Le Fort fractures, parotid salivary gland anatomy and pathology, and the anatomical layers of the scalp based on the lecture by Dr. Waleed Saudi.

Who is the instructor/author of the lecture presentation on the muscles of mastication and facial expression?

Waleed Saudi, M.D., MSMEd

What important clinical insight can a physician gain by observing a patient's face?

A physician can gain important information about an individual's general health.

What is the primary action of the muscles of facial expression?

They move the face.

What is the primary action of the muscles of mastication?

They move the jaw (temporomandibular joint).

What are the two actions performed by the extra-ocular muscles?

They move the eyeball and open the upper eyelid.

What is the functional role of the muscles of the middle ear?

They adjust the movement of the middle ear bones.

What is the primary action of the muscles of the soft palate?

They elevate and depress the palate.

What are the two primary actions of the muscles of the tongue?

They move and change the contour of the tongue.

What are the pharyngeal arches and what anatomical regions do they contribute to?

They are paired structures associated with the pharynx that contribute greatly to the formation of the face, jaw, ear, and neck.

Which cranial nerve is associated with pharyngeal arch 1?

CN V (trigeminal nerve).

Which cranial nerve is associated with pharyngeal arch 2?

CN VII (facial nerve).

Which cranial nerve is associated with pharyngeal arch 3?

CN IX (glossopharyngeal nerve).

Which cranial nerve and specific branch are associated with pharyngeal arch 4?

CN X (superior laryngeal branch of the vagus nerve).

Which cranial nerve and specific branch are associated with pharyngeal arch 6?

CN X (recurrent laryngeal branch of the vagus nerve).

What four muscles comprise the primary muscles of mastication?

Masseter, temporalis, medial pterygoid, and lateral pterygoid.

From which pharyngeal arch are the muscles of mastication derived?

The first pharyngeal arch.

Which specific nerve division innervates all muscles of mastication?

Branches of the mandibular division of the trigeminal nerve ($V_3$).

What are the respective origins of the superficial and deep heads of the masseter muscle?

Superficial origin: lower border of the zygomatic arch; Deep origin: medial portion of the zygomatic arch.

What are the three insertion sites of the masseter muscle?

Lateral surface of the ramus, coronoid process, and angle of the mandible.

What is the primary function of the masseter muscle during mastication?

Elevation of the mandible during the closing of the jaws.

How does the masseter muscle compare to the medial pterygoid muscle in terms of orientation and strength?

The masseter parallels the medial pterygoid muscle, but it is stronger.

What two muscles form the 'mandibular sling' around the angle of the mandible?

The masseter muscle (laterally) and the medial pterygoid muscle (medially).

What is the origin of the temporalis muscle?

Temporal fossa.

What are the two insertion points of the temporalis muscle?

Coronoid process and anterior border of the ramus of the mandible.

What are the two primary actions of the temporalis muscle on the mandible?

Elevates the jaw and retracts the mandible.

What is the origin of the medial pterygoid muscle?

Pterygoid fossa of the sphenoid bone.

Where does the medial pterygoid muscle insert?

Angle of the mandible.

What is the primary function of the medial pterygoid muscle?

Elevates the mandible.

What are the distinct origins of the superior and inferior heads of the lateral pterygoid muscle?

Superior head origin: greater wing of the sphenoid bone; Inferior head origin: lateral pterygoid plate.

What are the two insertion sites of the lateral pterygoid muscle?

Condylar neck and TMJ capsule.

What are the three primary actions of the lateral pterygoid muscle?

Protrusion of the mandible, depression of the mandible, and lateral deviation (to the opposite side).

To which side does the mandible deviate during unilateral contraction of the lateral pterygoid muscle?

To the opposite side.

What are the five primary movements of the mandible listed in the lecture?

1. Protrusion, 2. Retrusion, 3. Depression, 4. Elevation, and 5. Lateral deviation.

Which specific muscle of mastication produces mandibular protrusion?

Lateral pterygoid muscle.

Which muscle of mastication is responsible for retrusion of the mandible?

Temporalis muscle.

Which three muscles work together to elevate (close) the mandible?

Temporalis, masseter, and medial pterygoid.

Which muscle of mastication acts to depress (open) the mandible?

Lateral pterygoid muscle.

Which four skull bones constitute the midface buttress system?

Frontal, maxillary, zygomatic, and sphenoid bones.

Why is the facial buttress system clinically important for the midface?

The central midface contains many fragile bones that could easily crumble; thicker bones of the buttress system surround them to lend strength and stability.

What anatomical boundary defines a Le Fort I fracture?

A horizontal fracture through the maxilla that separates the dentoalveolar segment from the midface.

Which structures are involved in a Le Fort II fracture, and what segment results?

It involves the nasal bones, medial orbits, and maxilla, resulting in a pyramidal midface fragment.

Which structures are fractured in a Le Fort III pattern, and what separation occurs?

It involves the orbits and zygomatic arches, separating the midface from the skull base.

From which pharyngeal arch do the muscles of facial expression develop?

The second pharyngeal arch.

Which cranial nerve innervates all muscles of facial expression?

Branches of the facial nerve (CN VII).

In which anatomical plane do the muscles of facial expression reside, and where do they insert?

They reside in the superficial fascia and insert into the skin.

Why are the muscles derived from the second pharyngeal arch referred to as muscles of 'facial expression'?

Because these muscles control expressions of the face.

Which two muscles comprise the orbital group of facial expression?

Orbicularis oculi and corrugator supercilii.

What are the origin and insertion of the palpebral part of the orbicularis oculi muscle?

Origin: medial palpebral ligament; Insertion: lateral palpebral raphe.

What is the specific action of the palpebral part of the orbicularis oculi muscle?

Closes eyelids gently.

What are the origin and insertion of the orbital part of the orbicularis oculi muscle?

Origin: nasal part of frontal bone, frontal process of maxilla, and medial palpebral ligament; Insertion: fibers of ellipse around orbit.

What is the specific action of the orbital part of the orbicularis oculi muscle?

Closes eyelids forcefully.

Where is the corrugator supercilii muscle situated relative to the orbicularis oculi?

Deep to the superior part of the orbicularis oculi muscle in the eye region.

What are the origin and insertion of the corrugator supercilii muscle?

Origin: medial end of superciliary arch; Insertion: skin of medial half of eyebrow.

What facial action and wrinkle pattern are produced by the corrugator supercilii muscle?

Draws eyebrows medially and downward, causing vertical wrinkles as when a person frowns.

Which three muscles comprise the nasal group of facial expression?

Nasalis, procerus, and depressor septi nasi.

What are the origin and insertion of the transverse part of the nasalis muscle?

Origin: maxilla, lateral to nose; Insertion: aponeurosis across dorsum of nose with muscle from the other side.

What is the primary action of the transverse part of the nasalis muscle?

Compresses the nasal aperture.

What are the origin and insertion of the alar part of the nasalis muscle?

Origin: maxilla, over lateral incisor; Insertion: alar cartilage of nose.

What is the functional action of the alar part of the nasalis muscle?

Draws cartilage downward and laterally, opening the nostril.

Identify the nasal muscle highlighted in green across the bridge and alae of the nose.

Nasalis muscle

What are the origin and insertion sites of the procerus muscle?

Origin: nasal bone and upper part of the lateral nasal cartilage; Insertion: skin of lower forehead between eyebrows.

What action does the procerus muscle execute, and what wrinkle does it form?

Draws down the medial angle of the eyebrows and creates a transverse wrinkle over the bridge of the nose.

Identify the muscle highlighted in orange extending from the nasal bone to the lower forehead between the eyebrows.

Procerus muscle

What are the origin and insertion of the depressor septi nasi muscle?

Origin: incisive fossa of the maxilla; Insertion: nasal septum and back part of the alar part of nasalis muscle.

What three actions are produced by the depressor septi nasi muscle?

Depresses the nasal septum, constricts the nostril, and moves the apex of the nose during movement of the upper lip.

Identify the muscle highlighted in orange on the maxilla beneath the nasal cartilage.

Depressor septi nasi

What are the three subgroups included under the oral muscle group?

1. Orbicularis oris and buccinator, 2. Elevators of the lip, and 3. Depressors of the lip.

What are the origin attachments of the orbicularis oris muscle?

From other muscles in the area, and near the midline from the maxilla superiorly and the mandible inferiorly.

How do the fibers of the orbicularis oris muscle insert?

They form an ellipse around the mouth.

What three mechanical actions are performed by the orbicularis oris muscle?

Shapes and controls the size of the mouth opening, closes the lips, and protrudes the lips.

What clinical alteration occurs to the orbicularis oris muscle in patients with a smoking habit?

The muscle can show increased wrinkling (smoker lines) with cigarette use.

Why is observing orbicularis oris wrinkling clinically useful in dental/medical practice?

It can be useful to point out within tobacco cessation discussions.

What clinical intervention is utilized to ease peri-oral wrinkling associated with the orbicularis oris?

Botox injections.

What is the buccinator muscle and what facial structure does it form?

It is a thin quadrilateral muscle of facial expression that forms the anterior part of the cheek.

What are the two anatomical origin sites of the buccinator muscle?

Posterior part of the maxilla/mandible and the pterygomandibular raphe.

Where does the buccinator muscle insert?

It blends with the orbicularis oris and the lips.

What are the two primary actions of the buccinator muscle on the cheeks?

Presses the cheek against the teeth and compresses distended cheeks.

How does the buccinator muscle assist the muscles of mastication during chewing?

It keeps food pushed back on the occlusal surface of the posterior teeth.

What respiratory/vocal function does the buccinator muscle assist with?

The forceful expulsion of air from the cheeks.

What common clinical procedure routinely pierces the buccinator muscle?

Routine dental local anesthesia needles.

Where does the pterygomandibular raphe attach inferiorly on the mandible?

The posterior end of the mandible's mylohyoid line.

How is the pterygomandibular raphe noted clinically within the oral cavity?

As the pterygomandibular fold.

Which three muscles constitute the lower group of oral muscles (depressors of the lip)?

Depressor anguli oris, depressor labii inferioris, and mentalis.

During which specific emotional expression is the lower group of oral muscles active?

Frowning.

What is the origin of the depressor anguli oris muscle?

Oblique line of the mandible below the canine, premolar, and first molar.

Where does the depressor anguli oris muscle insert?

Skin at the corner of the mouth, blending with orbicularis oris.

What is the action of the depressor anguli oris muscle?

Draws the corner of the mouth down and laterally.

What is the origin of the depressor labii inferioris muscle?

Anterior part of the oblique line of the mandible.

Where does the depressor labii inferioris muscle insert?

Lower lip at the midline.

What is the action of the depressor labii inferioris muscle?

Draws the lower lip downward and laterally.

What are the origin and insertion of the mentalis muscle?

Origin: mandible inferior to incisor teeth; Insertion: skin of the chin.

What two actions are performed by the mentalis muscle?

Raises and protrudes the lower lip, and wrinkles the skin on the chin.

In which everyday actions does the mentalis muscle help position the lip?

When drinking from a cup or when pouting.

Which six muscles comprise the upper group of oral muscles (elevators of the lip)?

Risorius, levator labii superioris alaeque nasi, levator labii superioris, levator anguli oris, zygomaticus minor, and zygomaticus major.

What common expression is associated with the risorius muscle?

It is the smiling muscle and helps produce a grin.

What is the origin of the risorius muscle?

Fascia over the masseter muscle.

Where does the risorius muscle insert?

Skin at the corner of the mouth.

What is the functional action of the risorius muscle?

Retracts the corner of the mouth.

Identify the facial muscle highlighted in green extending horizontally across the cheek to the oral commissure.

Risorius muscle

What is the anatomical position of levator labii superioris alaeque nasi relative to levator labii superioris?

It is medial to the levator labii superioris.