adductor mandibulae

a muscle of the cheek area which acts to close the mouth and compress the lips. It is divided into four parts in the perch (Perca flavescens): part 1 has its origin on the dorsal half of the vertical arm of the preopercle and inserts at the centre of the maxillo-mandibular ligament (q.v.). It is a large muscle below the eye. A third part of the ligament serves as an origin for the fourth part of the muscle. Part 3 originates on the pterygoid bone and inserts with part 2 on the maxillo-mandibular ligament beneath the insertion of part 1. Part 2 is a large muscle below part 1. Part 4 originates on the internal portion of the maxillo-mandibular ligament and inserts on the ventral, internal part of the dentary and so is on the lower jaw