Muscles of Chewing and Swallowing

The following muscles contribute to facial expression and speech but are primarily concerned with manipulation of food, including tongue movements, chewing, and swallowing (table 10.3).

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

Frontalis

Procerus

Orbicularis oculi

Levator labii superioris Zygomaticus minor Zygomaticus major

Risorius

Depressor anguli oris Depressor labii inferioris

Platysma

Frontalis

Procerus

Orbicularis oculi

Labii Inferior

Galea aponeurotica

Figure 10.7 Muscles of Facial Expression. What muscle occupies the glabella?

Galea aponeurotica

Galea aponeurotica Temporalis

Occipitalis

Zygomatic arch Masseter

Sternocleidomastoid

Inferior pharyngeal constrictor

Levator scapulae Thyrohyoid Sternothyroid Omohyoid Sternohyoid

Figure 10.7 Muscles of Facial Expression. What muscle occupies the glabella?

Corrugator supercilii Nasalis

Levator anguli oris

Masseter

Buccinator

Orbicularis oris Mentalis

Frontalis

Corrugator supercilii

Orbicularis oculi Nasalis

Levator labii superioris

Zygomaticus minor Zygomaticus major

Orbicularis oris Mentalis

Depressor labii inferioris

Depressor anguli oris Risorius (cut) Buccinator

Saladin: Anatomy & I 10. The Muscular System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 10 The Muscular System 337

Table 10.2 Muscles of Facial Expression (see fig. 10.7)

O = origin, I = insertion, N = innervation (n. = nerve) Occipitofrontalis (oc-SIP-ih-toe-frun-TAY-lis)

Table 10.2 Muscles of Facial Expression (see fig. 10.7)

O = origin, I = insertion, N = innervation (n. = nerve) Occipitofrontalis (oc-SIP-ih-toe-frun-TAY-lis)

Occipitalis

Retracts scalp; fixes galea aponeurotica

O: superior nuchal line I: galea aponeurotica Frontalis

Raises eyebrows and creates wrinkles in forehead when occipitalis is contracted; draws scalp forward when occipitalis is relaxed O: galea aponeurotica I: skin of forehead

N: facial n. (VII) N: facial n. (VII)

Orbicularis Oculi (or-BIC-you-LERR-iss OC-you-lye)

Closes eye; compresses lacrimal gland to promote flow of tears O: medial wall of orbit I: eyelid

N: facial n. (VII)

Levator Palpebrae (leh-VAY-tur pal-PEE-bree) Superioris

Opens eye; raises upper eyelid

O: roof of orbit I: upper eyelid

N: oculomotor n. (III)

Corrugator Supercilii (COR-oo-GAY-tur SOO-per-SIL-ee-eye)

Medially depresses eyebrows and draws them closer together; wrinkles skin between eyebrows O: superciliary ridge I: skin of eyebrow

N: facial n. (VII)

Procerus (pro-SER-us)

Wrinkles skin between eyebrows; draws skin of forehead down

O: skin on bridge of nose I: skin of forehead

N: facial n. (VII)

Nasalis (nay-SAY-liss)

One part widens nostrils; another part depresses nasal cartilages and compresses nostrils O: maxilla and nasal cartilages I: bridge and alae of nose

N: facial n. (VII)

Orbicularis Oris (or-BIC-you-LERR-iss OR-iss)

Closes lips; protrudes lips as in kissing; aids in speech

O: muscle fibers around mouth I: mucous membrane of lips

N: facial n. (VII)

Levator Labii Superioris

O: zygomatic bone, maxilla I: upper lip

N: facial n. (VII)

Levator Anguli (ANG-you-lye) Oris

Elevates corners of mouth, as in smiling and laughing

O: maxilla I: superior corner of mouth

N: facial n. (VII)

Zygomaticus (ZY-go-MAT-ih-cus) Major and Zygomaticus Minor

Draw corners of mouth laterally and upward, as in smiling and laughing

O: zygomatic bone I: superolateral corner of mouth

N: facial n. (VII)

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Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

338 Part Two Support and Movement

Table 10.2 Muscles of Facial Expression (see fig. 10.7) (continued)

Risorius (rih-SOR-ee-us)

Table 10.2 Muscles of Facial Expression (see fig. 10.7) (continued)

Draws corner of mouth laterally, as in grimacing

O: fascia near ear I: corner of mouth

N: facial n. (VII)

Depressor Anguli Oris, or Triangularis

Depresses corner of mouth, as in frowning

O: mandible I: inferolateral corner of mouth

N: facial n. (VII)

Depressor Labii Inferioris

O: near mental protuberance I: lower lip

N: facial n. (VII)

Mentalis (men-TAY-lis)

Pulls skin of chin upward; elevates and protrudes lower lip, as in pouting O: near mental protuberance I: skin of chin

N: facial n. (VII)

Buccinator (BUCK-sin-AY-tur)

Compresses cheek; pushes food between teeth; expels air or liquid from mouth; creates suction O: lateral aspects of maxilla and mandible I: orbicularis oris

N: facial n. (VII)

Platysma (plah-TIZ-muh)

Depresses mandible, opens and widens mouth, tenses skin of neck

O: fasciae of deltoid and pectoralis major muscles I: mandible, skin of lower face, muscles at corners of mouth

N: facial n. (VII)

The tongue is a very agile organ. Both intrinsic and extrinsic muscle groups are responsible for its complex movements. The intrinsic muscles consist of variable numbers of vertical muscles that extend from the superior to inferior side of the tongue, transverse muscles that extend from left to right, and longitudinal muscles that extend from root to tip. The extrinsic muscles connect the tongue to other structures in the head and neck. These include the genioglossus,26 hyoglossus,27 styloglossus,28 and palatoglossus29 (fig. 10.8). The tongue and buccinator muscle shift food into position between the molars for chewing (mastication), and the tongue later forces the chewed food into the pharynx for swallowing.

There are four paired muscles of mastication: the temporalis, masseter, and medial and lateral pterygoids. The temporalis30 is a broad, fan-shaped muscle that arises from the temporal lines of the skull, passes behind the zygomatic arch, and inserts on the coronoid process

26genio = chin + gloss = tongue

27refers to the hyoid bone

28refers to the styloid process of the skull

29palato = palate

30refers to the temporal bone of the mandible (fig. 10.9a). The masseter31 is shorter and superficial to the temporalis, arising from the zygomatic arch and inserting on the lateral surface of the angle of the mandible (see fig. 10.7). It is a thick muscle easily palpated on the side of your jaw. The temporalis and masseter elevate the mandible to bite and chew food; they are two of the most powerful muscles in the body. Similar action is provided by the medial and lateral pterygoids. They arise from the pterygoid processes of the sphenoid bone and insert on the medial surface of the mandible (fig. 10.9b). The pterygoids elevate and protract the mandible and produce the lateral excursions used to grind food between the molars.

Several of the actions of chewing and swallowing are aided by eight pairs of hyoid muscles associated with the hyoid bone. Four of them, superior to the hyoid, form the suprahyoid group—the digastric, geniohyoid, mylohyoid, and stylohyoid. Those inferior to the hyoid form the infrahyoid group—the thyrohyoid, omohyoid, sternohyoid, and sternothyroid. (See fig. 10.8 for the geniohyoid and fig. 10.10 for the others.) Most of the hyoid muscles

31 masset = chew

Saladin: Anatomy & I 10. The Muscular System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 10 The Muscular System 339

Table 10.3 Muscles of Chewing and Swallowing (see figs. 10.8-10.10)

O = origin, I = insertion, N = innervation (n. = nerve)

Table 10.3 Muscles of Chewing and Swallowing (see figs. 10.8-10.10)

O = origin, I = insertion, N = innervation (n. = nerve)

Extrinsic Muscles of the Tongue

Genioglossus (JEE-nee-oh-GLOSS-us)

Depresses and protrudes tongue; creates dorsal groove in tongue that enables infants to grasp nipple and channel milk to pharynx

O: mental spines of mandible

I: hyoid bone, lateral aspect of tongue

N: hypoglossal n. (XII)

Hyoglossus

Depresses sides of tongue

O: hyoid bone

I: lateral aspect of tongue

N: hypoglossal n. (XII)

Styloglossus

Elevates and retracts tongue

O: styloid process

I: lateral aspect of tongue

N: hypoglossal n. (XII)

Palatoglossus

Elevates posterior part of tongue; constricts fauces (entry to pharynx)

O: soft palate

I: lateral aspect of tongue

N: accessory n. (XI)

Muscles of Mastication

Temporalis (TEM-po-RAY-liss)

Elevates mandible for biting and chewing; retracts mandible

O: temporal lines

I: coronoid process of mandible

N: trigeminal n. (V)

Masseter (ma-SEE-tur)

Elevates mandible for biting and chewing; causes some lateral excursion of mandible

O: zygomatic arch

I: lateral aspect of mandibular ramus and angle

N: trigeminal n. (V)

Medial Pterygoid (TERR-ih-goyd)

Elevates mandible; produces lateral excursion

O: pterygoid process of sphenoid bone

I: medial aspect of mandibular angle

N: trigeminal n. (V)

Lateral Pterygoid (TERR-ih-goyd)

Protracts mandible; produces lateral excursion

O: pterygoid process of sphenoid bone

I: slightly anterior to mandibular condyle

N: trigeminal n. (V)

Muscles of the Pharynx

Pharyngeal Constrictors (three muscles)

Constrict pharynx to force food into esophagus

O: mandible, medial pterygoid plate, hyoid bone, larynx

I: posterior median raphe (fibrous seam) of pharynx

N: glossopharyngeal n. (IX), vagus n. (X)

Hyoid Muscles—Suprahyoid Group

Digastric

Retracts mandible; elevates and fixes hyoid; depresses mandible when hyoid is fixed

O: mastoid notch and inner aspect of mandible near protuberance

I: hyoid, via fascial sling

N: trigeminal n. (V), facial n. (VII)

Saladin: Anatomy & I 10. The Muscular System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

340 Part Two Support and Movement

Table 10.3 Muscles of Chewing and Swallowing (see figs. 10.8-10.10) (continued)

Geniohyoid (JEE-nee-oh-HY-oyd)

Elevates and protracts hyoid; dilates pharynx to receive food; opens mouth when hyoid is fixed O: inner aspect of mental protuberance I: hyoid

N: hypoglossal n. (XII)

Mylohyoid

Forms floor of mouth; elevates hyoid; opens mouth when hyoid is fixed O: inferior margin of mandible I: hyoid

N: trigeminal n. (V)

Stylohyoid

O: styloid process I: hyoid

N: facial n. (VII)

Hyoid Muscles—Infrahyoid Group

Omohyoid

Depresses hyoid; fixes hyoid during opening of mouth O: superior border of scapula I: hyoid

N: ansa cervicalis

Sternohyoid

Depresses hyoid; fixes hyoid during opening of mouth O: manubrium, costal cartilage 1 I: hyoid

N: ansa cervicalis

Thyrohyoid

Depresses hyoid; elevates larynx; fixes hyoid during opening of mouth O: thyroid cartilage of larynx I: hyoid

N: hypoglossal n. (XII)

Sternothyroid

Depresses larynx; fixes hyoid during opening of mouth

O: manubrium, costal cartilage 1 or 2 I: thyroid cartilage of larynx

N: ansa cervicalis

receive their innervation from the ansa cervicalis, a loop of nerve at the side of the neck formed by certain fibers of the first through third cervical nerves.

The digastric32 arises from the mastoid process and thickens into a posterior belly beneath the margin of the mandible. It then narrows, passes through a connective tissue loop (fascial sling) attached to the hyoid bone, widens into an anterior belly, and attaches to the mandible near the protuberance. When it contracts, it pulls on the sling and elevates the hyoid bone. When the hyoid is fixed by the infrahyoid muscles, however, the digastric muscle opens the mouth. The mouth normally drops open by itself when the temporalis and masseter muscles are relaxed, but the digastric, platysma, and mylohyoid can open it more widely. The geniohyoid protracts the hyoid to widen the pharynx when food is swallowed. The mylohyoid33 muscles fuse at the midline, form the floor of the mouth, and work synergistically with the digastric to forcibly open the mouth. The stylo-hyoid, named for its origin and insertion, elevates the hyoid bone.

When food enters the pharynx, the superior, middle, and inferior pharyngeal constrictors contract in that order and force the food downward, into the esophagus. The thyrohyoid, named for the hyoid bone and large thyroid cartilage of the larynx, helps to prevent choking. It elevates the thyroid cartilage so that the larynx becomes sealed by a flap of tissue, the epiglottis. You can feel this di = two + gastr = belly mylo = mill, molar teeth

Saladin: Anatomy & I 10. The Muscular System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 10 The Muscular System 341

Palatoglossus Styloglossus

Inferior longitudinal muscle of tongue

Inferior Longitudinal Muscle

Figure 10.8 Muscles of the Tongue and Pharynx. Left lateral view.

Genioglossus Hyoglossus Geniohyoid Mylohyoid (cut) Hyoid bone Larynx Trachea

Styloid process Mastoid process Posterior belly of digastric (cut) Superior pharyngeal constrictor

Stylohyoid

Middle pharyngeal constrictor Posterior belly of digastric (cut)

Intermediate tendon of digastric (cut)

Inferior pharyngeal constrictor Esophagus

Figure 10.8 Muscles of the Tongue and Pharynx. Left lateral view.

Temporalis Muscle Flap
Figure 10.9 Muscles of Chewing. (a) Right lateral view. In order to expose the insertion of the temporalis muscle on the mandible, part of the zygomatic arch and masseter muscle are removed. (b) View of the pterygoid muscles looking into the oral cavity from behind the skull.

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

342 Part Two Support and Movement

Suprahyoid group

Infrahyoid group

Digastric Anterior belly Posterior belly

Stylohyoid Mylohyoid

Thyrohyoid

Omohyoid Superior belly Inferior belly

Sternohyoid Sternothyroid

Digastric Anterior belly Posterior belly

Stylohyoid Mylohyoid

Thyrohyoid

Omohyoid Superior belly Inferior belly

Sternohyoid Sternothyroid

Pics Scalenes

Hyoid bone Levator scapulae Scalenes

Trapezius Scalenes

Sternocleidomastoid Clavicle

Hyoid bone Levator scapulae Scalenes

Trapezius Scalenes

Sternocleidomastoid Clavicle

Geniohyoid Muscle

Figure 10.10 Muscles of the Neck. (a) The hyoid muscles, anterior view. The geniohyoid is deep to the mylohyoid and can be seen in figure 10.i (b) Left lateral view.

Stylohyoid Hyoglossus Mylohyoid

Anterior belly of digastric Hyoid bone Thyrohyoid

Superior belly of omohyoid Sternothyroid Sternohyoid

Figure 10.10 Muscles of the Neck. (a) The hyoid muscles, anterior view. The geniohyoid is deep to the mylohyoid and can be seen in figure 10.i (b) Left lateral view.

Posterior belly of digastric

Splenius capitis

Inferior pharyngeal constrictor

Sternocleidomastoid

Trapezius

Levator scapulae

Scalenes

Inferior belly of omohyoid effect by placing your fingers on your "Adam's apple" (a prominence of the thyroid cartilage) and feeling it bob up as you swallow. The sternothyroid then pulls the larynx down again. These infrahyoid muscles that act on the larynx are called the extrinsic muscles of the larynx. The larynx also has intrinsic muscles, which are concerned with control of the vocal cords and laryngeal opening (see chapter 22).

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Responses

  • carmelo
    What muscle depresses the hyoid and fixes it during opening of the mouth?
    6 years ago
  • Russom
    How to remove pimple lateral pterygoid muscle?
    6 years ago
  • Lena
    Where is the left lateral part of the tongue?
    6 years ago
  • Sayid Nuguse
    How to relax digastric muscle?
    4 years ago
  • nora fairbairn
    What produce lateral excursions of the mandible during chewing?
    4 years ago
  • pandora
    Which muscled help with chewing and swallowing?
    2 years ago

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