MANDIBLE AND EAR

• Mandibular foramen


  Medial surface, transmits the Inferior alveolar nerve and vessels
• Base


  Lower border of the body of the mandible
• Symphysis menti

  Faint ridge on the external midline surface of the body of the mandible, indicates the line of fusion of the two halves of the mandible
• Lateral temporomandibular ligament


  Strengthens the lateral aspect of the capsule, limits the movement of the mandible in a posterior direction and protects the external auditory meatus
• Capsule of the temporomandibular joint

  Surrounds the joint and is attached above to the articular tubercle and the margins of the mandibular fossa
• Lingula


  Projection in front of the mandibular foramen for the attachment of the SPHENOMANDIBULAR LIGAMENT
• Sphenomandibular ligament


  Lies on the medial side of the joint, attached above to the spine of the sphenoid bone, represents the remains of the first pharyngeal arch in this region
• Articular disk


  Divides the compartment, an oval plate that attaches circumferentially to the capsule, moves forward and backward with the head of the mandible during protraction and retraction
• Mandibular canal


  Opens on the lateral surface of the body of the mandible at the MENTAL FORAMEN
• Mandible

  • Largest and strongest bone of the face
  • Articulates with the skull at the TEMPOROMANDIBULAR JOINT
  • Consists of horizontal, horseshoe-shaped body and a pair of vertical rami
• Ramus of the mandible

  • Anterior CORONOID PROCESS and a posterior CONDYLOID PROCESS or HEAD
  • NECK inferior to the head
  • MANDIBULAR NOTCH separates the coronoid and condyloid processes
• Sublingual fossa


  Lies above the anterior part of the mylohyoid line
• Mental foramen


  Inferior to the second premolar tooth; transmits the terminal branches of the Inferior alveolar nerve and vessels
• Mental spines (genial tubercles)


  Midline medial surface of the body of the mandible, origin of GENIOGLOSSUS MUSCLE
• Stylomandibular ligament


  Lies behind and medial to the joint, a band of thickened deep cervical fascia that extends from the apex of the styloid process to the angle of the mandible
• Alveolar part


  Upper border of the body of the mandible, contains 16 sockets for the roots of the teeth in adults
• Submandibular fossa

  Superficial part of the submandibular salivary gland, lies below the posterior part of the mylohyoid line
• Temporomandibular joint

  Synovial articulation between the ARTICULAR TUBERCLE and the anterior portion of the MANDIBULAR FOSSA of the temporal bone above and the HEAD (CONDYLOID PROCESS) of the mandible below
• Digastric fossa


  A small, roughened depression on the base, on either side of the symphysis menti
• Mylohyoid line


  Oblique ridge that runs backward and laterally from the area of the mental spines to an area below and behind the third molar tooth
• Incisive canal


  Forward continuation of the mandibular canal beyond the mental foramen and below the incisor teeth
• External auditory (acoustic) meatus conducts sound waves from the auricle to the tympanic membrane
• Outer lateral third of the meatus is elastic cartilage, inner medial two-thirds are bony and formed by the tympanic plate of the temporal bone
• Middle ear converts airborne waveforms into solid-borne waveforms and transmits those to the internal ear
• Auricular muscles are essentially vestigial in humans
• Equilibrium translates fluid dynamics into a sense of balance
• External ear collects airborne vibrational waveforms
• External ear auricle (pinna) collects air vibrations
• TMJ relations

  • Anteriorly: Mandibular notch and masseteric nerve and artery
  • Posteriorly: Tympanic plate of the external auditory meatus and glenoid process of the parotid gland
  • Laterally: Parotid gland, fascia, and skin
  • Medially: Maxillary artery and vein and auriculotemporal nerve
• Movements of the mandible

  1. Mandible depression: Contraction of digastrics, geniohyoids, mylohyoids, lateral pterygoids pull the mandible forward

  2. Mandible elevation: Head of the mandible and the disc move backward, head rotates on the lower surface of the disc, contraction of temporalis, masseter, medial pterygoids

  3. Mandible protrusion: Articular disc is pulled forward, lower teeth drawn forward, contraction of lateral pterygoid muscles and medial pterygoids

  4. Mandible retraction: Contraction of posterior fibers of the temporalis, articular disc and head of the mandible pulled backward

  5. Lateral chewing movements: Alternately protruding and retracting the mandible on each side produces lateral motions, muscles work alternately on both sides
• External and middle ear structures function for sound conduction and transmission
• Lower surface of the disc

  Concave to fit the head of the mandible
• The meatus is lined by skin, and its outer third is provided with
• Disc movement during protraction and retraction of the mandible

  Disc moves forward and backward with the head of the mandible
• Upper surface of the disc

  Concavoconvex from anterior to posterior
• Hearing part of the internal ear converts solid-borne waveforms into fluid-borne waveforms, which are translated into sound
• Nerve supply to the mandible and ear
• Internal ear functions for sound perception and equilibrium
• Lymph drainage

  • Superficial parotid, mastoid, and superficial cervical lymph nodes
• Auriculotemporal nerve & Auricular branch of the vagus nerve innervate

  • Its outer surface