Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

The Musculoskeletal System
The Muscular System
Muscles of the Head

Depending on their Location and function, the Muscles of the HEAD are divided into two main groups: facial muscles and Muscles of Mastication. 

Facial muscles lie beneath the Skin and are arranged as sphincters and dilators around the oral and nasal apertures, the orbits, and the external acoustic meatus (Fig. 34). These muscles lack a superficial fascia; they originate from the bones of The Skull and insert into the Connective Tissue framework of the skin. Upon contraction, facial muscles shift the skin, alter its contours, and form dimples, furrows, and folds. In this way, they produce complex expressive facial movements, or mimicry. Facial muscles close and open the orifices they surround, and the resulting expressions reflect various emotional states and feelings—such as joy, grief, pain, shame, attention, and hope. According to their anatomical location, the paired facial muscles are subdivided into several groups: muscles of the cranial vault; Muscles surrounding the palpebral fissures; muscles surrounding the nostrils (nasal apertures); muscles surrounding the oral aperture; and auricular muscles.

Class="center">Muscle Groups of The Human Body

Fig. 34. Muscles of the Head and Neck. Right lateral view:

1 — tendon of the epicranial aponeurosis; 2 — frontal belly of the occipitofrontalis muscle; 3 — orbicularis oculi muscle; 4 — levator labii superioris muscle; 5 — levator anguli oris muscle; 6 — orbicularis oris muscle; 7 — zygomaticus major muscle; 8 — depressor labii inferioris muscle; 9 — depressor anguli oris muscle; 10 — risorius muscle; 11 — platysma; 12 — sternocleidomastoid muscle; 13 — trapezius muscle; 14 — auricularis posterior muscle; 15 — occipital belly of the occipitofrontalis muscle; 16 — auricularis superior muscle

The muscles of the cranial vault include the epicranius and the corrugator supercilii. The epicranius consists of two bellies (frontal and occipital) connected by a broad epicranial aponeurosis that is firmly fused with the scalp. The occipital belly originates from the Occipital bone, whereas the frontal belly blends into the skin of the forehead. Contraction of the frontal belly raises the eyebrows and forms transverse wrinkles on the forehead (often referred to as the muscle of surprise or inquiring attention). The occipital belly draws the entire muscle posteriorly, thereby smoothing out the forehead wrinkles. The corrugator supercilii originates from the nasal part of the Frontal bone and inserts into the skin of the eyebrow. When contracted bilaterally, these muscles draw the eyebrows together, producing expressions of pain, suffering, and gloom.

Surrounding the palpebral fissure is the orbicularis oculi muscle, formed by circular bundles encircling the Orbit (orbital part), blending into the skin of the eyelids (palpebral part), and attaching to the lacrimal sac (lacrimal part). Upon contraction, this muscle closes the eyelids, squints the eyes, and facilitates tear drainage into the nasolacrimal duct.

Surrounding the nasal apertures are the muscles of the Nose. These muscles, which constrict the nostrils, originate on the anterior surface of the Maxilla and insert into the ala and the cartilaginous part of the dorsum of the nose.

The muscles surrounding the oral aperture consist of fiber bundles located within the thickness of the Lips (sphincters) and radiating outwards relative to the oral fissure (dilators). Some dilators lie superior to the oral fissure (the levator anguli oris, levator labii superioris, and zygomaticus muscles). These muscles not only elevate the upper lip and the angle of the Mouth but also form expressions of smiling and laughing. Other muscles lie inferior to the oral fissure (the depressor anguli oris and depressor labii inferioris). Located here is also the mentalis muscle, which inserts into the skin of the chin and forms the chin dimple.

The buccinator muscle, which forms the muscular foundation of the cheek, belongs to the muscles that blend into the orbicularis oris. This muscle originates from the posterior Regions of the upper and lower jaws. It participates in sucking and in moving food boluses toward the Pharynx, and tenses the cheek, earning it the traditional name of the trumpeter's muscle.

Facial muscles also include the rudimentary auricular muscles (the anterior, superior, and auricularis posterior muscles), which are well-developed in animals, as well as the broad, flat platysma of the neck, among others.