Oral cavity

Overview and topographic anatomy

General information

  • •

    Oral cavity— the space located between the lips and cheeks on the external surface to the palatoglossal fold on the internal surface

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    The oral cavity is important in mastication, tasting, and talking

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    The area of the oral cavity can be divided into:

    • •

      Vestibule—the area between the teeth and lips or cheek

    • •

      Oral cavity proper—the area located internal to the teeth

  • •

    Posteriorly, the oral cavity is continuous with the oropharynx

  • •

    The hard palate and the soft palate are important boundaries within the oral cavity

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    The tongue is a major structure located on the oral cavity floor

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    All of the major salivary glands (parotid, submandibular, and sublingual) and minor salivary glands (lingual, palatal, buccal, and labial) empty into the oral cavity

  • •

    The muscles of the oral cavity include those of the mouth, cheeks, tongue, *

    * The muscles of the tongue are covered in Chapter 14 .

    and soft palate

  • •

    Waldeyer’s ring is the anatomic name for the ring of lymphatic tissue in the pharynx and oral cavity:

    • •

      Lingual tonsil (posterior third of tongue)

    • •

      Palatine tonsil (oropharynx)

    • •

      Tubal tonsil (nasopharynx)

    • •

      Pharyngeal tonsil (nasopharynx)

Figure 13-1

External anatomy

External features

Structure Comments
Lips

  • Divided into an upper and a lower lip that surround the opening of the oral cavity

  • Both lips have a muscular “skeleton” composed of the orbicularis oris m.

  • Upper lip is separated from the cheek by the nasolabial groove

  • Lower lip is separated from the chin by the labiomental groove

  • Upper and lower lips meet at the labial commissures

  • Vermilion zone —the red area of the lip that is clearly demarcated from the skin of the face at the vermilion border and is lined by a thinly keratinized layer of stratified squamous epithelium, which changes upon transition to the mucous membrane of the oral cavity; also known as the red zone

  • Philtrum —the depressed area located between the base of the nose and the vermilion border of the upper lip

  • Many mucus-secreting labial glands are located within the submucosal layer of the lips at the area of transition to mucous membrane of the oral cavity, which is nonkeratinized stratified squamous epithelium

  • Vestibule— the region between the lips or cheeks and the teeth

  • The fold of tissue created by the vestibule between the lip and teeth is called the vestibular or mucolabial fold

  • As the vestibular fold reflects on the alveolar bone holding the teeth, the mucous membrane abruptly changes into the gingiva

  • Within the vestibular fold are bands of tissue known as labial frenula

  • The labial frenula are pronounced at the maxillary and mandibular midline as the upper and lower frenula, respectively

  • Other accessory frenula are also located in the vestibule

Cheek

  • Located between the labial commissure and the mucosa overlying the ramus of the mandible

  • Has a muscular “skeleton” composed of the buccinator m.

  • Many mucus-secreting glands, known as buccal glands, are located within the submucosal layer of the inside of the cheeks, which is lined by mucous membrane of the oral cavity (nonkeratinized stratified squamous epithelium)

  • The vestibule continues from the region between the lips and teeth posteriorly, to be located between the cheek and the teeth

  • The fold of tissue created by the vestibule between the lip and the teeth is called the vestibular or mucobuccal fold

  • The retromolar region is the only area in which the vestibule and the oral cavity proper communicate

  • The parotid duct drains into the oral cavity at the parotid papilla, located along the mucous membrane of the cheek opposite the 2nd maxillary molar

  • Fordyce spots, ectopic sebaceous glands found in the mucosa of the cheeks appearing as yellowish spots, can be observed in the cheek

Figure 13-2

Vascular supply of the lips and cheek

ARTERIAL SUPPLY
Artery Source Comments
Superior labial branch of the facial Facial a. off the external carotid a.

  • Supplies the structures associated with the upper lip

  • Gives rise to the septal branch that travels to the nasal septum

Superior labial branch of the infraorbital Infraorbital a. off the maxillary a.

  • A continuation of the 3rd part of the maxillary a.

  • 1 of the 3 terminal branches of the infraorbital a., along with the inferior palpebral branch and the nasal branch

  • Accompanied by the nerve and vein of the same name

  • Helps supply the upper lip

Inferior labial branch of the facial Facial a. off the external carotid a.

  • Supplies the structures associated with the lower lip

Mental Inferior alveolar a.

  • A terminal branch from the inferior alveolar a., which arises from the 1st part of the maxillary a.

  • Emerges from the mental foramen to supply the chin region

Buccal Maxillary a.

  • A branch of the 2nd part of the maxillary a.

  • A small artery that runs obliquely in an anterior direction between the medial pterygoid and the insertion of the temporalis m. until it reaches the outer surface of the buccinator m. to supply that muscle and the face

Figure 13-3

VENOUS DRAINAGE
Vein Comments
Superior labial branch of the facial Drains the upper lip and joins the facial v.
Inferior labial branch of the facial Drains the lower lip and joins the facial v.
Mental Drains the chin and lower lip and joins the pterygoid plexus of veins
Buccal Drains the cheek and joins the pterygoid plexus of veins

Figure 13-4

Muscles

Muscle Origin Insertion Actions Nerve Comments
Orbicularis oris

  • Bone— anterior midline of the maxilla and mandible

  • Muscular— angle of the mouth where fibers blend with levator anguli oris, depressor anguli oris, zygomaticus major, and risorius mm.

Skin along the mouth

  • Closes lips

  • Protrusion of lips

  • Pursing of lips

Facial (buccal and mandibular branches)

  • Sphincter of the mouth

  • Muscle fibers encircle the mouth

Buccinator

  • Pterygomandibular raphe

  • Alveolar margins of the maxilla and mandible

  • Some fibers blend and provide origin for the orbicularis oris

  • Some fibers blend into the upper and lower lips

  • Aids in mastication, keeping the bolus between cheek and teeth

  • Helps forcibly expel air

  • Helps create a sucking action

Facial (buccal branch) Creates the framework of the cheek

Figure 13-5

Nerve supply

SENSORY INNERVATION
Nerve Source Course
  • ▪

    All sensory innervation to the skin of this region is supplied by the trigeminal n.

Superior labial branch of the infraorbital Infraorbital n. (a continuation of the maxillary division of the trigeminal n.)

  • 1 of the 3 terminal branches of the infraorbital n., along with the inferior palpebral and the nasal, as it exits onto the face via the infraorbital foramen

  • Supplies the skin of the upper lip

Mental Inferior alveolar n.

  • 1 of the 2 terminal branches of the inferior alveolar n.

  • Emerges through the mental foramen of the mandible in the region of the 2nd mandibular premolar

  • Supplies the skin of the lower lip, chin, and facial gingiva as far posteriorly as the 2nd mandibular premolar

Buccal branch of the mandibular division of the trigeminal Mandibular division of the trigeminal n.

  • Passes anteriorly between the 2 heads of the lateral pterygoid m.

  • Descends inferiorly along the lower part of the temporalis m. to emerge from deep to the anterior border of the masseter m.

  • Supplies the skin over the buccinator m. before passing through it to supply the mucous membrane lining its inner surface and the gingiva along the mandibular molars

Figure 13-6

Boundaries of the oral cavity

General information

Boundary Structure
Superior Hard palate
Posterosuperior Soft palate
Lateral Cheeks
Inferior The floor of the oral cavity (which is located along the lingual border of the mandible, forming a horseshoe-shaped region)

Figure 13-7

Superior border: Hard palate

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    The superior border (or roof) of the oral cavity is the hard palate, comprising the anterior 2/3 of the entire palate

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    Separates the oral cavity from the nasal cavity

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    Composed of:

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      Palatal process of the maxilla

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      Horizontal process of the palatine

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    In the anterior midline, an incisive foramen is located on the right and left sides that transmits the terminal branches of the nasopalatine nerve and sphenopalatine vessels

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    In the posterolateral region of the hard palate, the greater and lesser palatine foramina are located on the right and left sides; these openings transmit the greater and lesser palatine nn. and vessels

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    The bones of the hard palate are covered by a thick mucous membrane, known as masticatory mucosa (keratinized stratified squamous epithelium)

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    The mucous membrane has a small elevation in the anterior midline called the incisive papilla that overlies the incisive foramen

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    The mucous membrane in the anterior region is tightly attached to the underlying palatal process of the maxilla

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    The mucous membrane in the anterior region is frequently avulsed from the palatal process of the maxilla during the administration of a nasopalatine nerve block

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    Moving posteriorly from the incisive papilla, the mucous membrane has a thick midline palatal raphe

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    Lateral transverse ridges called transverse rugae (plicae) are located along the mucous membrane of the hard palate

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    Deep to the mucous membrane of the hard palate are numerous mucus-secreting glands called palatal (palatine) glands

Figure 13-8

Posterosuperior border: Soft palate

  • •

    The posterosuperior border of the oral cavity is the soft palate

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    The soft palate is the continuation of the palate posteriorly and makes up approximately one-third of the entire palate

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    The soft palate separates the oral cavity from the oropharynx

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    An abundance of mucus-secreting palatal glands, which are continuous with the hard palate, are located in the soft palate

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    The soft palate has 3 margins:

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      Anteriorly, it is continuous with the hard palate at the vibrating line

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      Posterolaterally, it forms the superior portion of the palatoglossal and palatopharyngeal folds

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      Posteriorly, the uvula hangs in the center of the posterior free margin

  • •

    The thick palatine aponeurosis forms the foundation of the soft palate

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    The soft palate is composed of 5 muscles:

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      Musculus uvulae

    • •

      Tensor veli palatini

    • •

      Levator veli palatini

    • •

      Palatopharyngeus

    • •

      Palatoglossus (sometimes considered in the grouping of tongue muscles)

  • •

    The soft palate helps close off the nasopharynx during deglutition by forming a seal at the fold of Passavant

Figure 13-9

MUSCLES OF THE SOFT PALATE
Muscle Origin Insertion Actions Nerve Supply Comment
Tensor veli palatini

  • Cartilaginous part of the auditory tube

  • Scaphoid fossa of the sphenoid

Palatine aponeurosis Pulls the soft palate laterally, which broadens it Mandibular division of the trigeminal n. The tendon of the tensor veli palatini m. wraps around the pterygoid hamulus
Musculus uvulae

  • Posterior nasal spine

  • Palatine aponeurosis

Fibers insert into the mucosa of the uvula

  • Retracts uvula

  • Pulls uvula in a posterosuperior direction

Pharyngeal plexus (the motor portion of this plexus is formed by the pharyngeal branch of the vagus n.) May be bifid
Levator veli palatini

  • Cartilaginous portion of the auditory tube

  • Petrous portion of the temporal bone

  • Palatine aponeurosis

  • Fibers also insert into the muscle of the opposite side

  • Elevates soft palate

  • Pulls soft palate posterosuperiorly, which acts to help close the nasopharynx

The levator veli palatini m. passes through an aperture superior to the superior constrictor m.
Palatopharyngeus

  • Posterior border of hard palate

  • Palatine aponeurosis

Posterior border of the lamina of the thyroid cartilage

  • Elevates the pharynx and larynx

  • Acts to help close the nasopharynx

Grouped either with soft palate muscles or with muscles of the pharynx
Palatoglossus Palatine aponeurosis (oral surface) Lateral aspect of the tongue where some fibers intermix with the transverse m. and some along the dorsal surface of the tongue

  • Elevation of the root of the tongue

  • Narrows the oropharyngeal isthmus for deglutition

Grouped either with extrinsic muscles of the tongue or with muscles of the soft palate

Figure 13-10

Figure 13-11

Lateral border: Cheek

  • •

    The lateral border of the oral cavity extends anteriorly from the labial commissure, posteriorly to the ramus of the mandible

  • •

    Superior limit of the cheek is the maxillary vestibule; inferior limit is the mandibular vestibule

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    Mucous membrane of the cheek is stratified squamous epithelium

  • •

    Fordyce spots are ectopic sebaceous glands that may be observed on the inner surface of the cheek

  • •

    Parotid papilla is located in the cheek opposite the maxillary 2nd molar

  • •

    Pterygomandibular raphe is located in the posterior portion and serves as a landmark for the pterygomandibular space for inferior alveolar nerve blocks

Figure 13-12

Inferior border: Floor of the oral cavity

  • •

    The inferior border is the floor of the oral cavity

  • •

    It is located along the lingual border of the mandible forming a horseshoe-shaped region

  • •

    The mylohyoid m. serves as the sling of the floor of the oral cavity, and structures superior to it are the major contents

  • •

    The largest structure is the tongue and related musculature

  • •

    Please see Chapter 14 on the tongue for a detailed explanation of the musculature of the tongue

Structure Comments
Tongue
Lingual frenulum

  • A midline fold of tissue located at the base of the tongue and extending along the inferior surface of the tongue

Mucous membrane

  • Stratified squamous epithelium that extends from the tongue to the mandible

Sublingual papilla

  • A swelling located on both sides of the lingual frenulum at the base of the tongue

  • Continuous with the sublingual folds overlying the sublingual glands on the floor of the oral cavity

  • Marks the entrance of the saliva from the submandibular glands into the oral cavity

Submandibular duct

  • Lies along the sublingual gland under the mucosa

Lingual n.

  • Crosses the submandibular duct passing laterally, inferiorly, and medially to the duct to reach the tongue and supply general sensation to the anterior 2/3

Plica fimbriata

  • Fimbriated folds located lateral to the lingual frenulum

Mylohyoid m.

  • Forms the muscular sling of the floor of the oral cavity

  • Passes from the mylohyoid line of the mandible to the opposite mylohyoid m. in the midline at the mylohyoid raphe and attaches posteriorly to the hyoid bone

Geniohyoid mm. Lie superior to the mylohyoid mm.
Attach from the inferior genial tubercles of the mandible to the hyoid bone
MUSCLES OF THE FLOOR OF THE ORAL CAVITY
Muscle Origin Insertion Actions Nerve Supply Comment
Mylohyoid Mylohyoid line of the mandible

  • Mylohyoid raphe

  • Body of the hyoid bone

  • Raises the floor of the oral cavity

  • Can elevate the hyoid bone

Mylohyoid n. from the inferior alveolar branch of the mandibular division of the trigeminal n. Forms the sling of the oral cavity
Geniohyoid Inferior genial tubercle Body of the hyoid bone Elevates the hyoid bone C1 ventral ramus, which follows the hypoglossal n. Superior to the mylohyoid m.

Figure 13-13

Teeth

General information

  • •

    Teeth are hard structures attached to the jaws and involved primarily in eating

  • •

    2 arches contain the teeth:

    • •

      Maxillary arch

    • •

      Mandibular arch

  • •

    Humans have 2 sets of teeth during a lifetime:

    • •

      Deciduous teeth—the primary dentition

    • •

      Permanent teeth—the secondary dentition

  • •

    Between the ages of 6 and 12 years, there is a mixed dentition, in which both primary and permanent teeth are present in the oral cavity at the same time

Deciduous teeth

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    There are 20 total deciduous teeth: 2 incisors, 1 canine, and 2 molars in each of the 4 quadrants of the oral cavity

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    The primary dentition is represented by the formula I 2 2 C 1 1 M 2 2 , which specifies the total number of teeth (10) on each side of the oral cavity

  • •

    No deciduous teeth are present at birth; however, by the 3rd year of life, all 20 deciduous teeth have erupted

Permanent teeth

  • •

    There are 32 total permanent teeth: 2 incisors, 1 canine, 2 premolars, and 3 molars in each of the 4 quadrants of the oral cavity

  • •

    The permanent dentition is represented by the formula I 2 2 C 1 1 P 2 2 M 3 3 , which specifies the total number of teeth (16) on each side of the oral cavity

  • •

    The 1st permanent tooth to erupt into the oral cavity normally is the mandibular 1st molar

    • •

      This eruption occurs at about 6 years of age

    • •

      It erupts distal to the primary dentition

  • •

    The deciduous (primary) teeth eventually are replaced by the permanent teeth

  • •

    The replacement teeth are termed succedaneous teeth

SURFACES OF A TOOTH
Labial The surface of the anterior teeth that is closest to the lip
Buccal The surface of the posterior teeth that is closest to the cheek
Facial Used as a synonym for labial or buccal
Lingual Opposite the tongue in the mandibular arch and opposite the hard palate of the maxillary arch
Mesial Closest to the midline of the dental arch
Distal Farthest from the midline of the dental arch
Occlusal Used for chewing in posterior teeth
Incisal The cutting edge of anterior teeth

Surfaces of a tooth

Figure 13-14

Basic anatomy of a tooth

Crown

  • Anatomic crown —the portion of the tooth that has a surface of enamel

  • Clinical crown— the portion of the tooth that is exposed within the oral cavity

Root

  • Anatomic root— the portion of the tooth that has a surface of cementum

  • Clinical root— the portion of the tooth that is entrenched within the maxilla or mandible and is not exposed to the oral cavity

Apex of the root

  • The end tip of the root, which is also the location of a small aperture at the point of each root, which provides an entrance for the neurovascular connective tissue into the pulp cavity

Cervical line

  • The anatomic demarcation between the crown and the root

  • It often is termed the cementoenamel junction (CEJ)

Enamel

  • The hard, shiny surface of the anatomic crown

  • The hardest portion of the tooth

  • Made of small hexagonal rods, called enamel prisms, that are parallel to one another

Cementum

  • A thin, dull layer on the surface of the anatomic root

  • Similar in structure and chemical composition to bone

  • With age, cementum increases in thickness

Dentin

  • The hard tissue that underlies both the enamel and cementum and constitutes the major portion of the tooth

  • A modification of osseous tissue

  • Composed of a number of dental tubules (small wavy and branching tubes) that are located in a dense matrix

Cusp

  • An elevation on the occlusal surface of molars and premolars that makes up a divisional part of the tooth

  • The incisal edge of canines is referred to as a cusp and is used for prehension (grasping and tearing) of food

Pulp cavity

  • Contains the dental pulp (highly neurovascular connective tissue)

  • Separated into the pulp chamber , located in the coronal portion of the tooth, and the pulp canal , located in the root portion of the tooth

Cingulum

  • A convex elevation that is located on the lingual surface of the crowns of anterior teeth just incisal to the CEJ

Figure 13-15
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Feb 15, 2025 | Posted by in General Dentistry | Comments Off on Oral cavity

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