184 Anatomy & Physiology Essentials Copyright Goodheart-Willcox Co., Inc. neck muscles are paired—one on the right and one on the left. The head and neck muscles are displayed in Figure 6-13, and their locations and functions are summarized in Figure 6-14. Facial Muscles The frontalis muscle is so named because it covers the frontal bone of the skull. It attaches the epicranial aponeurosis to the skin above the eyebrows, enabling elevation of the eyebrows and wrinkling of the fore- head. On the posterior side, the epicranial aponeurosis is attached to the temporal bone by the occipitalis muscle. Contraction of the occipitalis pulls the scalp posteriorly. The orbicularis oculi and orbicularis oris respectively surround the eyes and mouth. The orbicularis oculi enables closing and squinting of the eyes. Orbicularis oris contracts to close the mouth and extend the lips as in kissing. T here are more than 650 skeletal muscles in the human body. This section presents only the most important muscles from the standpoint of functional movement. Almost all of these muscles are arranged in agonist-antagonist pairs, causing opposing actions at one or more joints. Muscles of the Head and Neck The muscles of the head and neck can be divided into three groups: facial muscles, chewing muscles, and neck muscles. The difference between facial muscles and most other muscles is that the insertions of facial muscles connect them to other muscles or skin rather than a bone. When these muscles contract, pulling on the skin, they produce an array of facial expressions. With the exception of the orbicularis oris, which encircles the mouth, and the sheetlike platysma on the front and sides of the neck, all of the head and Sternocleidomastoid Frontalis Orbicularis oculi Nasalis Platysma Zygomaticus Orbicularis oris Buccinator Temporalis Occipitalis Epicranial aponeurosis Masseter © Body Scientific International Figure 6.13 Major muscles of the head and neck.