Lymphatic drainage from the face primarily moves toward three groups of lymph nodes (Fig. 8.69): submental nodes inferior and posterior to the chin, which drain lymphatics from the medial part of the lower lip and chin bilaterally; submandibular nodes superficial to the submandibular gland and inferior to the body of the mandible, which drain the lymphatics from the medial corner of the orbit, most of the external nose the medial part of the cheek, the upper lip, and the lateral part of the lower lip that follows the course of the facial artery; pre-auricular and parotid nodes anterior to the ear, which drain lymphatics from most of the eyelids, a part of the external nose, and the lateral part of the cheek.
The scalp is the part of the head that extends from the superciliary arches anteriorly to the external occipital protuberance and superior nuchal lines posteriorly. Laterally it continues inferiorly to the zygomatic arch.
The scalp is a multilayered structure with layers that can be defined by the word itself:
S—skin,
C—connective tissue (dense),
A—aponeurotic layer,
L—loose connective tissue, and
P—pericranium (Fig. 8.70).
Examining the layers of the scalp reveals that the first three layers are tightly held together, forming a single unit. This unit is sometimes referred to as the scalp proper and is the tissue torn away during serious “scalping” injuries.
The skin is the outer layer of the scalp (Figs. 8.70 and 8.71). It is similar structurally to skin throughout the body with the exception that hair is present on a large amount of it.
Deep to the skin is dense connective tissue. This layer anchors the skin to the third layer and contains the arteries, veins, and nerves supplying the scalp. When the scalp is cut, the dense connective tissue surrounding the vessels tends to hold cut vessels open. This results in profuse bleeding.
The deepest layer of the first three layers is the aponeurotic layer. Firmly attached to the skin by the dense connective tissue of the second layer, this layer consists of the occipitofrontalis muscle, which has a frontal belly anteriorly, an occipital belly posteriorly, and an aponeurotic tendon— the epicranial aponeurosis (galea aponeurotica)—connecting the two (Fig. 8.72).
The frontal belly of the occipitofrontalis begins anteriorly where it is attached to the skin of the eyebrows. It passes upward, across the forehead, to become continuous with the aponeurotic tendon.
Posteriorly, each occipital belly of the occipitofrontalis arises from the lateral part of the superior nuchal line of the occipital bone and the mastoid process of the temporal bone. It also passes superiorly to attach to the aponeurotic tendon.
The occipitofrontalis muscles move the scalp, wrinkle the forehead, and raise the eyebrows. The frontal belly is innervated by temporal branches of the facial nerve [VII] and the posterior belly by the posterior auricular branch.
A layer of loose connective tissue separates the aponeurotic layer from the pericranium and facilitates movement of the scalp proper over the calvaria (Figs. 8.70 and 8.72). Because of its consistency, infections tend to localize and spread through the loose connective tissue (also see “In the clinic” on p. 878).
The pericranium is the deepest layer of the scalp and is the periosteum on the outer surface of the calvaria. It is attached to the bones of the calvaria but is removable, except in the area of the sutures.