Look at how your jaw ends up when saying first syllable of ‘Lateral’ or ‘Medial’ :
- –“La”: your jaw is now open, so Lateral opens mouth.
- –“Me”: your jaw is still closed, so medial closes the mandible.
Origin : deep head: medial side of lateral pterygoid plate behind the upper teeth
superficial head: pyramidal process of palatine bone and maxillary tuberosity
Insertion : medial angle of the mandible
Actions : elevates mandible, closes jaw, helps lateral pterygoids in moving the jaw from side to side
Origin : Great wing of sphenoid and pterygoid plate
Insertion : Condyle of mandible
Actions : depresses mandible, Protrude mandible, side to side movement of mandible