Final answer:
The platysma muscle is responsible for pulling the lower lip inferiorly and tensing the skin of the neck. It is a superficial muscle that extends from the chest to the jawline and is involved in facial expressions and neck tension.
Step-by-step explanation:
The muscle that pulls the lower lip inferiorly and tenses the skin of the neck is the platysma. This muscle is not mentioned in the provided reference material, but based on general anatomical knowledge, the platysma is known for these actions. The platysma is a superficial muscle that stretches from the chest and shoulder muscles (clavicle and deltoid) up to the jawline (mandible), covering the cervical region and lower face.
When the platysma contracts, it depresses the lower lip and mandible, which contributes to facial expressions such as frowning, and it also tensions the skin of the neck. Other nearby muscles include the sternocleidomastoid that contributes to head movement and the suprahyoid and infrahyoid muscle groups that are involved in swallowing and speech actions as mentioned.