of the chin and chin elevation. There may be a small separation between the left and right bodies of this muscle, causing a dimpled or clefted appearance of the chin. The platysma muscle extends from the superficial fascia of the chest inferior to the clavicle and travels over the anterolateral neck and mandible to insert with the muscles of the lower lip. It is also continuous with the SMAS of the lower face. Contraction of the platysma leads to tensing of the skin of the neck, and it derives its innervation from the cervical branch of the facial nerve [1, 13].

Summary: Soft Tissue Components of the Scalp

and Face

•The scalp consists of five soft tissue layers including the skin, connective tissue (fat), aponeurosis (galea aponeurotica), loose connective tissue (subgaleal compartment), and periosteum.

•The soft tissue structures of the face include the skin, the superficial and deep subcutaneous fat, superficial fascia, and deep fascia.

•The superficial musculoaponeurotic system, or SMAS, is a fibromuscular layer which connects to the overlying skin via vertically oriented fibers, allowing the muscles and soft tissues of the face to move together as a unit.

30.4Soft Tissue Components of the Scalp and Face

30.4.1 Scalp

The scalp consists of five soft tissue layers which can be easily remembered using the pneumonic “SCALP.” This denotes the skin (epidermis and dermis), connec-

tive tissue (fat), aponeurosis (galea aponeurotica), loose connective tissue (subgaleal compartment), and periosteum (Fig. 30.11). The fatty layer of the scalp consists of collections of fat lobules separated by fibrous septae which connect the skin to the underlying galea, creating a dense, compact structure. Blood vessels, nerves, and lymphatics travel within the fibrous septae in the subcutaneous layer. The septae bind tightly to scalp blood vessels, inhibiting vasospasm and rapid hemostasis in the event of scalp injury. The galea of the scalp is a strong, dense, inelastic connective tissue layer and is contiguous with the SMAS of the face. It also serves as an aponeurosis between the frontalis and occipitalis muscles as described previously. Anteriorly, the galea inserts into the supraorbital ridge, and posteriorly, it attaches to the highest nuchal line. Laterally, it envelops the temporoparietalis muscle and is contiguous with the temporalis fascia. Dissection and undermining beneath the galea is relatively simple given the loose, relatively avascular areolar tissue in the subgaleal space, allowing for increased scalp mobility for closures [1, 8].

30.4.2 Face

The soft tissue structures of the face include the skin, the superficial and deep subcutaneous fat, superficial fascia, and deep fascia. The superficial facial fat lies superiorly to the SMAS and is composed of distinct compartments including the central, middle, and lateral temporal-cheek fat of the forehead and cheek and the jowl fat of the lower face [15]. Fibrous septae divide fatty lobules and compartments. These septae are extensions of superficial fascia, and nerves and blood vessels course within them. The superficial fatty layer tends to vary in thickness depending on region and the