hnL2 - muscles of mastication

• identify the main muscles of mastication:

  masseter

  temporalis

  medial pterygoid

  lateral pterygoid
• describe the origins of the masseter:

  (superficial belly) the anterior 2/3 zygomatic arch, inferior border.
• describe the insertion of the masseter:

  along the lower border of the angle of the mandible, fibres run at 45 degree angle.
• describe the nerve supply of the masseter:

  fibres run vertically
• describe the action of the masseter:

  close the jaws by elevating and drawing forwards the angle of the mandible.
• describe the origins of the masseter (deep belly):

  the posterior 1/3 of the zygomatic arch
• describe the insertion of the masseter (deep belly):

  along the ramus at the angle of the mandible
• describe the origins of the temporalis:

  the temporal fossa within the inferior temporal line
• describe the insertion of the temporalis:

  the coronoid process of the mandible and the inner anterior aspect of the ramus to the retro-molar area.
• describe the nerve supply of the temporalis:

  vertical and horizontal fibres
• describe the action of the temporalis:

  close jaw by elevating the mandible (vertical fibres)

  retracting the mandible (horizontal fibres)
• describe the origins of the medial pterygoid:

  the medical surface of the lateral pterygoid plate(deep head) with some fibres from the maxillary tuberosity (superficial head)
• describe the insertion of the medial pterygoid:

  inner angle of the mandible.

  the muscle follows the same line as masseter, but on the inside of the mandible.
• describe the actions of the medial pterygoid:

  to close the jaw by pulling the angle of the mandible upwards and forwards.

  to move the mandible towards the opposite side by pulling.
• describe the origins of the lateral pterygoid:

  from the infratemporal surface of the skull (superior head) and from the lateral pterygoid plate of the sphenoid bone (inferior head).
• describe the insertion of the lateral pterygoid:

  the neck of the condyle, with some fibres passing into the articular capsule and disc of the TMJ.
• describe the action of the lateral pterygoid:

  opens the mouth by drawing the condyle and dics forwards from the mandibular fossa down the slope of the articular tubercle.

  it is necessary for the ACTIVE opening of the mouth.
• list the accessory muscles of mastication:

  suprahyoid muscles:

  • digastric
  • anterior belly - mandibular div trigeminal (digastric fossa)
  • posterior belly - facial nerve (mastoid notch)
  • mylohyoid
  • geniohyoid, stylohyoid

  infrahyoid muscles:

  • the strap muscles of the neck
  • sternohyoid
  • sternithyroid
  • thyrohyoid
  • omohyoid