What is the primary muscle responsible for the opening of the mouth?

The primary muscle responsible for the opening of the mouth is the anterior belly of the digastric muscle. This muscle plays a crucial role in depressing the mandible, which allows the mouth to open. Along with its counterpart, the posterior belly of the digastric, it assists in actions such as swallowing and speaking.

The anterior belly of the digastric originates from the digastric fossa of the mandible and inserts into the body of the hyoid bone. When it contracts, it effectively pulls the mandible downward, which is essential for the action of mouth opening, such as during chewing or when discussing various dental procedures.

In contrast, the mylohyoid muscle primarily contributes to forming the floor of the mouth and helps elevate the hyoid bone rather than actively opening the mouth. The anterior temporal muscle is primarily responsible for elevating the mandible and closing the jaw, while the posterior temporal muscle is involved in retracting the mandible. Thus, these muscles work primarily in closing and stabilizing the jaw rather than facilitating its opening.