Final answer:
The muscle that pushes the lower lip up and wrinkles the chin is the orbicularis oris. The mental protuberance is the structure that forms the chin. The masseter muscle is key in moving the lower jaw for chewing.
Step-by-step explanation:
The muscle at the tip of the chin that pushes the lower lip up and wrinkles the chin is technically located around the mouth. Its name is the orbicularis oris. This is a circular muscle whose function is primarily involved in the movement of the lips. Specifically, it closes the mouth and puckers the lips when it contracts. Additionally, when you pout or purse your lips, it is the orbicularis oris that enables these actions.
The forward projection at the lower edge of the anterior mandible, which forms the chin, is called the mental protuberance. This isn't a muscle, but rather an anatomical structure. Muscles of the face and jaw, unlike most muscles in the body, often insert into the skin instead of bone. This allows for nuanced movements of the face for various facial expressions.
A muscle called the masseter muscle, located within the cheek, plays a key role in chewing as it elevates the mandible (lower jaw) to close the mouth. The masseter, along with the temporalis muscle, provide the jaw the large leverage required for the biting and chewing of food.
Learn more about Muscles of the face