Oral Cavity, Tongue and Muscles of Mastication

• Oral cavity


  Initial part of gastrointestinal tract

  
• Oral cavity


  • Receives secretions from salivary glands
  • Parts: vestibule and oral cavity proper

  
• Vestibule


  • Outer narrow space situated inside the lips and cheek and outside the teeth and gums
  • Communicates freely with the oral cavity proper
  • Communicates with the exterior through oral fissure
  • Receives parotid duct from parotid salivary gland

  
• Oral cavity proper


  • Continuous anteriorly with vestibule
  • Continuous posteriorly with pharynx
  • Roof formed by hard and soft palate
  • Floor contains tongue
  • Anterior part below tongue contains sublingual region

  
• Sublingual region


  Receives the openings of sublingual and submandibular ducts
• Teeth


  • Form part of masticatory apparatus
  • Fixed to the jaws
  • Adults have 32 permanent teeth
  • Children have 20 deciduous or milk teeth

  
• Tooth surfaces


  Vestibular, lingual, mesial, distal and occlusal

  
• Parts of tooth


  Crown, root and neck

  
• Crown


  Part projecting outside the gum
• Root


  • Fixed in the tooth socket by the periodontal ligament
  • Anchor the tooth to the jaw bone and act as shock absorbers

  
• Neck


  Situated between root and crown and surrounded by gum
• Tooth structure


  • Enamel - hard outer layer of crown
  • Dentine - forms bulk of tooth, can be sensitive
  • Cementum - bone-like tissue covering root
  • Pulp cavity - contains connective tissue, blood vessels and nerves
  • Pulp canal (root canal) - transmits nerves and vessels to and from pulp cavity

  
• Nerve supply of teeth

  • Upper jaw - anterior, middle and posterior superior alveolar nerves from maxillary nerve
  • Lower jaw - inferior alveolar nerves from mandibular nerve
• Blood supply of teeth

  Superior and inferior alveolar arteries from maxillary artery
• Palate


  Structure forming roof of oral cavity and separating it from nasal cavity
• Parts of palate


  • Hard palate and soft palate
• Hard palate


  • Hard anterior part of palate made up of bones
  • Separates nasal cavity from oral cavity
  • Formed by palatine process of maxilla and horizontal plate of palatine bones
  • Has posterior margin giving attachment to soft palate
  • Inferior surface has incisive fossa
  • Supplied by greater palatine arteries and nerves

  
• Soft palate


  • Posterior part of palate
  • Movable, muscular fold suspended from posterior border of hard palate
  • Separates nasopharynx from oropharynx
  • Has anterior and posterior surfaces, superior and inferior borders
  • Superior border attached to hard palate
  • Inferior border free and contains uvula
• Muscles of soft palate

  • Tensor palati
  • Levator palati
  • Palatoglossus
  • Palatopharyngeus
  • Musculus uvulae
• Nerve supply of soft palate

  • Sensory - lesser palatine and glossopharyngeal nerves
  • Motor - pharyngeal branch of vagus via pharyngeal plexus, except tensor palati which is supplied by mandibular nerve
• Blood supply of soft palate

  Lesser palatine arteries and veins
• Functions of soft palate


  • Separates oropharynx from nasopharynx during swallowing
  • Isolates oral cavity from oropharynx during chewing so breathing is not affected
  • Modifies voice quality by varying degree of closure of pharyngeal isthmus
  • Protects nasal mucosa during sneezing
  • Prevents entry of sputum into nose during coughing
• Paralysis of soft palate muscles results in nasal regurgitation of liquids, nasal twang in voice, and deviation of uvula opposite to the side of lesion