III. The Articulatory System Muscles of the Face and Mouth

The Articulatory System The articulatory system is dominated by three significant structures: the lips, the tongue, and the velum. Movements of the lips are a product of the muscles of the face, while those of the tongue and velum utilize extrinsic and intrinsic muscles of the oral cavity.

Muscles of Facial Expression There are 10 muscles in the oro-facial region which comprise the muscles of facial expression used for laughing, smiling, pouting, etc. They also play a role in vegetative functions. The 5 muscles we will discuss originate from the bones of the facial skeleton and insert into the soft tissue or muscles of the face, particularly those of the mouth and lips. They are supplied by the Facial (VII) cranial nerve.

Zygomatic Muscles The zygomatic major muscle beings at the zygomatic bone and descends rather obliquely into the upper lip at the angle of the mouth. It draws the corner of the mouth up and backward, especially during laughter.

Risorius Muscles The risorius muscles originate in the connective tissue just lateral to the zygomatic muscle. Its fibers course horizontally to insert into the skin at the angle of the mouth. Their action is to retract the angle of the mouth. Together with the zygomatic muscle, smiling is accomplished.

Mental Muscles The mental or mentalis muscles originate from a depression in the mandible just below the lower lip. The fibers descend into the skin of the chin. They act to protrude the lower lip or wrinkle the skin of the chin in disdain.

Orbicularis Oris This muscle has no origin or insertions. It is essentially a layer of muscle fiber derived from the other muscles that insert into the lips. A circular muscle group, these fibers encompass the periphery of the mouth. Upon contraction, they act like a drawstring, closing the mouth and pursing or puckering the lips.

Buccinator Muscles These muscles constitute the cheek--the lateral wall of the buccal cavity. They originate from the posterior alveolar processes of the maxillae and mandible. The fibers pass forward to converge and insert into the deep muscle layer of the lip. The act to compress the cheek, force air from the mouth, or keep food from slipping off the teeth during chewing.

Muscles of the Nose In humans, the muscles of the nose play a minimal role in respiration and speech. They may, however, be rather significant mediators of secondary cues of facial expression, for such behaviors as sneering.

Muscles of Mastication There are four pairs of muscles utilized for mastication and they are all innervated by the Vth trigeminal cranial nerve. In general, they originate on the bones of the cranium and insert into the mandible. Their actions are to cause chewing movements, such as up-and-down and back-and-forth (grinding) movements of the mandible against the maxillae.

Muscles of Mastication Although these muscles primary function is masticatory, their secondary function is articulatory. Fairly good jaw closure must be available to produce many of the speech sounds, such as plosives and some of the fricatives. The size and shape of the oral cavity is also one of the determinants of vowel characteristics.

Temporalis Muscles These muscles originate on the temporal bone. The radiating fibers converge downward forming a tendon that passes beneath the zygomatic arch. It inserts on the anterior border of the coronoid process and the ramus of the mandible. The action of these muscles is to elevate and retract the mandible, to close the jaw.

Masseter Muscles The masseter muscles arise from the zygomatic arch and insert into the lateral surface of the angle of the mandible. The action of the masseter muscle is to raise the mandible against the maxillae for closing.

Internal (Medial) Pterygoid Muscles These muscles have their origin at the pterygoid process of the sphenoid bone. The fibers pass downward, laterally, and backward to insert in the ramus and the angle of the mandible. These muscles elevate the mandible for closure and protrudes it.

External (Lateral) Pterygoid Muscles These muscles originate from the wing of the sphenoid bone. They run horizontally to insert into the neck of the condyloid process of the mandible. When contracted, they depress the mandible to open the jaw or protrude it. When operating singly, they provide lateral movement of the mandible.

Muscles of the Soft Palate (Velum) The soft palate, velum, is essentially a soft-tissue extension of the hard palate. It further divides the oral from the nasal cavity. It provides for changes in the volume and shape of the two cavities. In the action of velopharyngeal closure, the velum moves to separate the naso- from the oro-pharynx. Five muscles make up the major part of the palate.

Muscles of the Soft Palate (Velum) The various muscles entering the palate arise from skeletal structures in the immediate vicinity. Because of their various origins—some superior, some inferior, and some posterior—its possible for the palate to be moved back, up, and down, or in some combination thereof.

Levator Veli Palatini Muscles Innervated by the Xth vagus cranial nerve, the levator veli palatini gets its name from the action it performs upon the soft palate—lifting and elevating. It originates from the temporal bone and inserts into the soft palate, fanning out at the midline along its entire length.

Levator Veli Palatini Muscles Innervated by the Xth vagus cranial nerve, the levator veli palatini gets its name from the action it performs upon the soft palate—lifting and elevating. It originates from the temporal bone and inserts into the soft palate, fanning out at the midline along its entire length.

Levator Veli Palatini Muscles As the fibers from each side interweave at the midline, upon contraction, it works like a slingshot to raise the velum toward the posterior pharyngeal wall, narrowing the pharyngeal isthmus.

Tensor Veli Palatini Muscles Innervated by the Vth trigeminal cranial nerve, the tensor veli palatini gets its name from the action it performs upon the soft palate—tensing. This muscle pair has a very strange origin. Fibers run from the posterior hard palate to the hamulus of the sphenoid bone, curve around it.

Tensor Veli Palatini Muscles Some fibers then insert laterally into the wall of the Eustachian tube. Others pass forward and downward around the hamulus and enter the velum much as the levator muscle does. The action of the tensor is to make the velum taut and to dilate the orifice of the Eustachian tube.

Uvula Muscle The uvula muscle is comprised of paired bands of muscle fibers that originate along the posterior nasal spine as well as from the palatal aponeurosis. The fibers run along side the midline of the soft palate to insert into the uvula itself. It serves to shape the uvula upon contraction. It is innervated by the Vagus nerve.

Palatoglossus Muscle Innervated by the Vagus nerve, the palatoglossus muscle passes from the back sides of the tongue to the palate along the sides of the oral cavity. They insert into the palatal aponeurosis.

Palatoglossus Muscle These bundles form the anterior faucial pillars. Upon contraction, this muscle draws down the sides of the soft palate and up on the tongue for the production of nasal sounds.

Palatopharyngeal Muscle Innervated by the Vagus nerve, the palatopharyngeal muscle originates on the posterior border of the thyroid cartilage near the superior cornu. Its fibers pass superiorly to insert into the palatal aponeurosis.

Palatopharyngeal Muscle These muscle bundles form the posterior faucial pillars. Contraction of this muscle pulls down on the velum and up on the larynx. During swallowing, it provides a faucial sphincter, pulling the faucial pillars medially to prevent food from backing up and out of the pharynx.

Muscles of the Tongue The tongue is variously called the major organ of speech, taste, and swallowing. In structure, it is almost entirely muscular. There are both extrinsic and intrinsic muscles that make up the tongue.

Muscles of the Tongue The tongue can be divided into many functional parts. Those divisions include the tip (apex), blade, body, dorsum, and root. The tongue tip is involved in the production of over 50% of all speech sounds.

Muscles of the Tongue The tongue blade is the flat surface of the tongue just behind the tip. It is only directly involved in a few speech sounds, but it helps shape the tongue for many others.

Muscles of the Tongue The tongue body is the main part of the tongue, lying below the hard and soft palate. The position of the tongue body in the mouth is used to describe where the tongue is producing vowels, e.g., /u/ high back.

Muscles of the Tongue The tongue dorsum is the back part of the tongue. It is used to contact the back part of the hard and soft palates to make vowels and many consonants.

Muscles of the Tongue The tongue root is the lowest part of the tongue in the throat. It helps to form the front of the pharynx. It is not directly involved in the production of any English sounds but helps shape the vocal tract.

Extrinsic Muscles Extrinsic muscles of the tongue originate from adjacent skeletal structures but insert into the tongue. They are primarily responsible for the tongue’s movements from place to place within the oral cavity.

Extrinsic Muscles All the extrinsic tongue muscles are innervated by the hypoglossal (XII) cranial nerve. There are four pairs of extrinsic lingual muscles.

Styloglossus Muscle The styloglossus muscles originate from the styloid process of the temporal bone and insert into the lateral border of the tongue. Upon contraction, it retracts and raises the base of the tongue.

Genioglossus Muscles The genioglossus muscles form a large part of the tongue. Its shape resembles a tipped fan. It originates from the interior midline of the mandible. Its fibers fan out along the length of the tongue.

Genioglossus Muscles The most anterior fibers run to the tongue tip and are responsible for withdrawing the tip into the mouth and depressing it. The medial fibers making up the bulk of the tongue draw the base forward for protruding the tip through the teeth.

Hyoglossus Muscles The hyoglossus muscles originate from the hyoid bone and extend superiorly to insert into the posterior half of the sides of the tongue. Upon contraction, it depresses the sides of the tongue.

Palatoglossus Muscles As an extrinsic muscle of the tongue, the palatoglossus muscles originate from the back sides of the tongue and extend superiorly to insert into the palatal aponeurosis. When they contract, they pull up on the base of the tongue, and down on the soft palate, to reduce the oropharyngeal opening. They are innervated by the Vagus nerve.

Intrinsic Muscles The intrinsic muscles of the tongue originate and insert into the tongue and provide for changes in its shape. The intrinsic lingual muscles are named by the plane of direction in which their fibers run within the tongue. They are all innervated by the XII (hypoglossal) nerve.

Superior Longitudinal Muscle The superior longitudinal muscle is an unpaired muscle runing the length of the tongue, just below a layer of mucous membrane. Upon contraction, this muscle will shorten the tongue, and turn the tip upward. This action is extremely important for articulation of /t/, /d/, /l/, and /n/ phonemes.

Inferior Longitudinal Muscle The unpaired inferior longitudinal muscle runs between the genioglossus and hyoglossus muscles on the undersurface of the tongue. Upon contraction, this muscle will shorten the tongue, and turn the tip downward. This action is extremely important for articulation of phonemes that are made with the tongue tip down, such as /s/.

Transverse Muscle The transverse muscle runs from side to side between the two longitudinal muscles. When contracted, the transverse muscle narrows and elongates the tongue and elevates its lateral borders.

Upon contraction, it flattens and broadens the tongue. Vertical Muscle The vertical muscle is found at the borders of the tongue running from the upper to the under surface of the structure. Upon contraction, it flattens and broadens the tongue. It is important in vowel production.