What is the masseter muscle?

The masseter muscle is an important component of the masticatory muscles and is primarily located on the outer side of the mandibular angle bilaterally. It originates from the lower border and inner surface of the zygomatic arch and inserts on the masseteric tuberosity and the lateral surface of the ramus of the mandible. The muscle runs obliquely downward and posteriorly, has a rectangular shape, and consists of two heads—superior and inferior. The primary function of the masseter muscle is elevating the mandible, thereby closing the mouth. It works in coordination with other muscles such as the temporalis and medial pterygoid to accomplish chewing movements. The size and degree of development of the masseter muscle are influenced by various factors, including ethnicity, gender, age, and facial shape. Individuals who frequently chew hard foods tend to have more developed and hypertrophied masseter muscles. Masseteric hypertrophy may be associated with bony enlargement of the mandibular angle, resulting in a wider lower face. For cases of masseteric hypertrophy, improvement can be achieved through interventions such as botulinum toxin injections (commonly known as "face-slimming injections") or surgical procedures.