Anatomy of the Human Oral Cavity

• Notes cover the human oral cavity, its boundaries, sub-sites, teeth, and related structures

Boundaries

• Anterior border: lip
• Lateral border: buccal mucosa
• Posterosuperior border: junction of hard and soft palate
• Posterolateral border: retromolar trigone
• Posteroinferior border: circumvallate papillae

Subsites of the Oral Cavity

• Includes the lip, buccal mucosa, upper/lower dentoalveolar ridges, floor of the mouth, oral tongue, and hard palate

Lip

• Blood supply is from the superior and inferior labial arteries
• The orbicularis oris muscle is present
• Motor innervation: Facial n. (CN VII)
• Sensory innervation: Trigeminal n. (CN V)
  • Upper lip: anterior and middle superior alveolar nerves from V2
  • Lower lip: mental nerve from V3
• Lymphatic drainage: submandibular nodes

Lip Histology and Composition

• Outer lining: keratinized stratified squamous epithelium and lacks labial glands
• Vestibule lining: non-keratinized stratified squamous epithelium
• Internally contains labial glands and minor salivary glands between mucous membrane and orbicularis oris muscle

Buccal Mucosa

• Located on the sides of the oral cavity
• It lines the cheeks and lips where they touch the teeth
• It extends from the posterior aspect of the lip to the alveolar ridges medially, and the pterygomandibular fold posteriorly
• Lined by non-keratinized stratified squamous epithelium

Upper and Lower Dentoalveolar Ridges/Alveolar Ridges

• The mucogingival junction is where the vestibular mucosa from the inner lining of the lip tightly binds to the alveolar bone, also known as the vestibular sulcus

Sensory Innervation of the Alveolar Ridges

• Uses the Trigeminal n. (CN V)
  • Upper alveolar ridge V2
  • Lower alveolar ridge Inferior Alveolar Nerve (V3) of CN V
• Molars: posterior superior alveolar nerve from the pterygopalatine fossa
• Molars and premolars: middle superior alveolar nerve from the infraorbital nerve
• Incisors and canines: anterior superior alveolar nerve from the infraorbital nerve
• Gums of the molars and bicuspids on the palatal side: greater palatine nerve
• Gums of the incisors and canines on the palatal side: nasopalatine nerve
• Gums of the molars and bicuspids: buccal nerve of CN V

Floor of the Mouth

• The mucosal surface is bordered by the anterior ⅔ of the oral tongue, the alveolar ridge laterally and anteriorly, and the anterior tonsillar pillar and lingual frenulum posteriorly, dividing the region into two oval spaces
• Contains the submandibular gland duct and sublingual papilla
• Innervation: lingual nerve of CN V3

Oral Tongue

• Divided into anterior ⅔ and posterior ⅓, divided by the palatoglossal arch
• It has V-shaped sulcus terminalis and circumvallate papillae lying anterior to the sulcus
• The foramen caecum is the point of origin of the thyroid gland
• Embryologically formed from ectodermal stomodeum (anterior ⅔) and endodermal foregut (posterior ⅓)

Innervation of the Tongue

• Sensory: lingual nerve (V3) for anterior ⅔, CN IX for base of tongue
• Taste: chorda tympani (CN VII) for anterior ⅔, CN IX for base of tongue
• Motor: hypoglossal nerve for both anterior ⅔ and base of tongue

Tongue Papillae

• Fungiform: resemble a mushroom
• Filiform: threadlike papillae, more numerous and smaller than fungiform, and lack taste buds
• Circumvallate

Extrinsic Muscles of the Tongue

• Styloglossus elevates and retracts the tongue
• Hypoglossus depresses the tongue
• Genioglossus protrudes the tongue, depresses its center
• Palatoglossus elevates back of the tongue

Intrinsic Muscles of the Tongue

• Longitudinal runs from hyoid bone to tip and moves the tip of the tongue
• Transversus goes across the tongue, narrows and lengthens it
• Verticalis elevates and depresses the tongue, flattening it

Blood Supply and Lymphatic Drainage of the Tongue

• Lingual artery is medial to the hyoglossus muscle
  • Dorsal lingual artery supplies the base, and the deep lingual artery supplies the body
• Tip drains to the submental glands bilaterally
• Dorsum drains to the submandibular gland and jugulodigastric lymph node (LN)

Hard Palate

• Covered by mucoperiosteum
• Anterior: incisive papillae and palatine process of the maxilla
• Posterior: horizontal plates of the palatine bone
• The incisive foramen (Foramina of Stenson) is an exit point for the nasopalatine nerve and descending palatine artery

Hard Palate Foramen

• Greater palatine foramen: exit point of greater palatine artery, vein, and nerve
• Lesser palatine foramen: exit point of lesser palatine artery, vein, and nerve

Teeth

• Primary function is to tear and chew food
• Parts: enamel (outermost covering), cementum (covers the root), dentin (under enamel and cementum), periodontal ligaments (hold tooth in place), and pulp root (contains vessels/nerves)

Dental Fillings and Root Canals

• Fillings applicable as long as the dentin area remains
• Root canals: Damage reaches the pulp root requiring boring/streaking downward to kill vessels/nerves

Tooth Surfaces

• Lingual: inner surface
• Buccal/labial: outer surface
• Mesial: towards the midline
• Distal: away from the midline
• Occlusal: top surface
• Incisal: cutting surface
• Gingival: towards the gumline
• Pulpal: towards the center

Deciduous Teeth (Baby Teeth)

• Erupt at 6 months
• There are 5 per quadrant

Permanent Teeth

• Formed between ages 6-12 years
• There are 8 per quadrant

Dental Numbering System

• Numbered from 1-32
• It is viewed from the dental practitioner's viewpoint starting from the distalmost right maxillary teeth
• 1 is the upper right wisdom tooth, and 32 is the lower right wisdom tooth
• 16 is the left upper 3rd molar