Masseter Muscle and Mid-Pupillary Line

The masseter muscle is a good starting point. It is the large muscle of mastication that occupies the lateral portion of the cheek below the zygomatic arch (Figure 1.1). The parotid gland rests on this muscle. At its anterior border on a line drawn from the tragus to the middle of the upper cutaneous lip, the parotid duct can be identified as it dips inward piercing the buccinator muscle to open into the mouth at the level of the second upper molar. Also, at the jaw line, just at the anterior border of the lower masseter muscle, the facial artery and vein enter onto the face. Pulsation of the artery is often possible at this location. The superficial temporalis artery pulse can be felt just anterior to the ear at its superior attachment. Just beyond this it splits into superior and parietal branches.

Figure 1.1 Surface landmarks based on the masseter muscle.

The mid-pupillary line is identified with the patient sitting up and gazing straight ahead. Three important openings in the skull can be located (Figure 1.2). The superior orbital foramen is located at the superior orbital rim. Through it exits the important supraorbital neurovascular complex. Similarly, the infraorbital foramen, about 1 cm below the inferior orbital rim, contains the infraorbital neurovascular artery, vein and sensory nerve. Finally, the mental foramen, located in the alveolar bone of the mandible in the mid-pupillary line, contains the mental artery, vein and nerve. The exact location of all three of these orifices is important when performing respective nerve blocks of the sensory nerves exiting them.

Figure 1.2 Surface landmarks: the mid-pupillary line.

Relaxed Skin Tension Lines (RSTL)

The lines and wrinkles that develop with age and sun exposure become an easily recognizable road map of the face. These wrinkles and creases, first noted as hyperanimation smile lines or frown (scowl) lines, may become permanently etched as elastic tissue degenerates and becomes ineffective in resisting the pull of the underlying muscles of facial expression. These are referred to as the relaxed skin tension lines (RSTL) (Figure 1.3) and run perpendicular to the exertion of the mimetic muscles below. These lines are often the best choice for the placement of elective scar lines on the face. When they are readily apparent, no problem is posed in designing scar orientation. In younger people, having them animate by grimacing, wrinkling the forehead, smiling or puckering will usually expose the RSTL sufficiently to make the correct choice. Similarly, pinching the skin from various directions will also reveal the flow of the RSTL. Scars not oriented within or parallel to the RSTL are generally more noticeable, as they don’t go with “flow” of the region. This is especially apparent when the patient is smiling or going through some other active form of dynamic emotional expression.

Figure 1.3 Relaxed skin tension lines of the face.

Cosmetic Units and Junction Lines

One of the major conceptual advances over the past decade or so in reconstructive and aesthetic surgery is the refinement and widespread acceptance of the junction lines and cosmetic (aesthetic) units of the face (Figure 1.4). Cosmetic unit junction lines are the lines on the face at the borders of the cosmetic units. They include the well-defined melo-labial fold that separates the cheek from the lip, the mental-labial crease that divides the chin from the cutaneous lower lip, the hairline, and the jaw line. More subtle junction lines separate the cheek from the nose (nasofacial) and lower eyelid from the cheek. The nose has several subunits defined by the alar groove, the dorsal crests and the nasofacial line. Collectively, these are the outlines that caricaturists use along with exaggerated features (broad forehead, wide-set eyes, protruding nose) to rapidly define an individual’s countenance and personality. They are also the best location for camouflaging scars. Since lines and shadows are anticipated in these areas, scars tend to visually disappear when placed within them. Conversely, scars crossing junction lines are all too noticeable.

Figure 1.4 Cosmetic units and junction lines of the face.

Cosmetic units are the areas cordoned off by the junction lines. They share common characteristics of skin color and texture, pore opening size, elasticity, thickness, and presence or absence of hair. The cheek, temple, chin, and eyelids are their own well-defined units, whereas the nose, cheek, and ear can be subdivided into smaller units. The nose in particular has been defined to include the root, the dorsum, the lateral side walls, the paired alae nasi, and the tip.

Several useful principles of closure have been derived from the conceptualization scheme noted above. These include:

Free Margins: Concept of Tension Vector of Closure

Another important concept when performing facial surgery is that of the free margins; the eyebrows, eyelids, lips and nostril rims. These are important as they offer little resistance to the forces of wound closure and can be easily distorted by excess tension. This can occur from the immediate direct exertion of tension by a side-to-side closure or the delayed application of tension as a second intention healing wound or split thickness graft site contracts. The resulting asymmetries can be both cosmetically unsettling and functionally disabling. Ectropion of the lower lid can lead to permanent visual problems while eclabion and lack of a proper oral seal can cause problems with phonation and eating/drinking while looking unsightly.

The tension vector of closure can be favorably manipulated by one of several techniques:

Concavities and Convexities: Implications for Second Intention Healing

The face is not a flat structure. Rather, it is composed of undulating well-defined elevations and depressions that need to be taken into consideration when planning closures. Scar lines that traverse from convexity to concavity may contract in an unbecoming manner and may require preplanning with an S-plasty configuration for appropriate closure. However, the major effect of whether an area is flat, concave or convex determines how well defects resolve when allowed to heal by second intention. Although the size and depth of the defect have some impact on the final healing, defects on concave surfaces such as the temple, the medial canthus and the alar groove do well, whereas defects on convex surfaces such as the malar eminence, the tip of the nose and the chin generally heal poorly with webbed or elevated scars. Defects on flat surfaces, such as the forehead or cheek typically respond somewhere inbetween.

Introduction

One of the things that separates humans from other animals is the ability to communicate by use of the muscles of facial expression (the mimetic muscles). By use of this silent mode of interacting, human discourse is enriched by nuance and subtlety. Shades of annoyance, reverie, indifference, skepticism, sarcasm, etc, are molded onto the spoken word.

Muscles of facial expression are unique in that they are the only muscles to insert into the skin. They do so via fibrous septae that connect the superior portion of the muscle to the undersurface of the dermis. They also insert or interdigitate with the other mimetic muscles. So while the frontalis muscle wrinkles the forehead and raises the eyebrow, it also helps open the eye widely by partially inserting into the upper fibers of the orbicularis oculi muscle (Figure 1.6).

Figure 1.6 Muscles of facial expression. (a) Anterior view. (b) Lateral view.

Innervation of the muscles is exclusively by branches of the facial or cranial nerve VII. This occurs at the lateral undersurface of the muscle. The muscles are most effective and concentrated in the mid-plane of the face and exert their major effect around the two major orifices of the face; the eyes and the mouth. The aponeurotic component tends to be more laterally displaced on the face in the superficial musculoaponeurotic system (SMAS) of the cheek and the superficial temporalis fascia of the temple. The other major component of the aponeurotic system, the galea aponeurotica is spread over the expanse of the skull, connecting the anteriorly displaced frontalis muscle with the occipitalis muscle of the neck.

Muscles Acting around the Eyelids

The frontalis muscle is the primary muscle of the forehead and its main function is to wrinkle the skin of the forehead and elevate the eyebrow. Accordingly, it has been called the “surprise” muscle. It also, through its interdigitations with the upper fibers of the orbicularis oculi muscle, assists in opening the eye widely. Injury to the temporalis muscle results in flattening the skin of the forehead, brow ptosis, and accentuation of the effects of dermatochalasis and upper visual field gaze.

The corrugator supercilii muscle has come under intense interest recently with widespread popularity of botulinum toxin injections. The muscle originates from the frontal bone of the medial orbit in line with and just above the medial canthal tendon insertion. It has two slips; the oblique head that runs a short distance superiorly to insert into the skin of the medial eyebrow and helps depress the medial brow and the larger transverse head that runs laterally to insert widely into the skin of the eyebrow. It functions mainly to pull the eyebrow medially and slightly downward to create the vertical scowl lines of the glabella. Recently, the depressor supercilii has been described. It arises just above and deep to the corrugator supercilii and extends vertically superior to also attach into the skin of the medial eyebrow. It appears that there are three muscles that act in concert to depress the medial eyebrow: the most deeply placed depressor supercilii, the middle oblique head of the corrugator supercilii, and the vertically oriented fibers of the medial/superior orbicularis oculi muscle.

The key to the orbital region is the large, sphincter-like circumferential orbicularis oculi muscle. It has both outer orbital and inner palpebral portions. The orbital portion originates broadly from the superior and inferior bony orbital rims and inserts into the medial and lateral canthal tendons as well as the superficial temporalis fascia. It also interdigitates with fibers from the frontalis, corrugator supercilii, and procerus muscles. The orbital division is under voluntary control and acts to close the eye tightly and depress the eyebrow. Unilateral contraction results in a wink. The palpebral portion over the orbital septum and tarsal plate acts to gently close the eye (voluntary) or blink (involuntary). The muscle is innervated by fibers of the temporal and zygomatic branches of the facial nerve.

Muscles Acting around the Nose

The nose is relatively devoid of musculature when compared with the eyes and lips. They consist mainly of the procerus muscle that extends down from the frontalis vertically onto the upper nose across the root and into the aponeurosis of the nasalis muscle on the nasal dorsum. Contraction, usually in concert with the adjacent lip elevators, “scrunches” up and shortens the nose and causes the transverse RSTL across the root. The levator labii superioris alaeque nasi arises from the maxilla under the medial orbicularis oculi and descends vertically to the mid-upper lip, but also sends slips to the lateral ala nasi. In concert with alar fibers of the nasalis muscle, it aids in dilating the nostril with each inspiration. The broad thin nasalis muscle is the intrinsic nasal muscle with alar fibers just discussed, transverse fibers over the dorsum that just tense the skin over the dorsum, and the depressor septi portion that pulls down the septum and aids in deep inspiration.

Muscles Acting around the Mouth

As noted earlier, the mouth is the most expressive part of the face. This is due to the myriad number of muscles that insert not only into the overlying skin, but also insert and exert motion from every possible direction into the sphincter-like orbicularis oris muscle. Further modulation of fine muscular movement is aided by a structure called the modiolus (hub, Latin), from which the orbicularis originates. Lying about 1 cm lateral to the oral commissure, it is a muscular platform-like confluence of several of the muscles inserting into the orbicularis and acting on the corner of the mouth, including the zygomaticus major, levator anguli oris, risorius, depressor anguli oris, buccinator, and platysma muscles. Actions are amplified or muted by fine-tuning of the synergistic and antagonistic muscles. The action of the orbicularis muscle itself is to draw the lips together and to pucker the lips.

There are four lip elevators; from most medial to lateral they include the levator labii superioris alaeque nasi, levator labii superioris, zygomaticus major, and zygomaticus minor. They are all important in smiling, sneering and snarling movements. The upper lip and corner of the mouth are retracted and elevated by the risorius and levator anguli oris muscles. The buccinator muscle, beloved by trumpet players, plays an important role in chewing by keeping food tucked inward between the teeth.

The muscles working on the lower lip include the mentalis muscle, which wrinkles the skin of the chin and also helps pouch out and protrude the lower lip (sniveling); the depressor anguli oris, which retracts and depresses the corner of the mouth; and the depressor labii inferioris muscle, which, as the name implies, depresses the lower lip. The latter two are important (along with the upper lip elevators and angle retractors) in attaining the wide, happy toothy grin associated with laughing. The marginal mandibular nerve innervates all three muscles. Finally, the platysma muscle, innervated by the cervical nerve, stretches broadly from the chest upward across the expanse of the neck over the jaw line to blend with the angle of the mouth depressors. Despite being thin in some people, it helps cover and protect the marginal mandibular nerve at the anterior border of the masseter muscle at the jaw line.

Introduction

There are two kinds of muscles of the face: the muscles of facial expression and the skeletal muscles of mastication (pterygoid, masseter, and temporal muscles). The former are innervated entirely by the facial (VIIth cranial) nerve, whereas the latter are supplied by motor fibers of the trigeminal (Vth cranial) nerve. Only the facial nerve has clinical relevance to dermatologic surgeons and will be the topic of this section.

Facial Nerve

The facial nerve is a complex structure with an anatomy that varies from patient to patient. The possibility of injuring or severing one of the branches of this nerve is of paramount importance in every procedure performed on the face, whether extirpating a tumor, repairing the defect after removing the tumor, or performing cosmetic “lifting” procedures. The consequences of such a dire event can be cosmetically and functionally devastating for the patient and a source of medical– legal concern for the surgeon. It is well to know the projected pathway and expected depth within the skin of all the motor nerves within the surgical field not only to attempt to avoid them, but also to include during the informed consent process a discussion of the potential consequences of injuring them.

After leaving the interior skull at the stylomastoid foramen, the facial nerve classically divides into two major trunks within the substance of the parotid gland, the superior temporofacial and the inferior cervicofacial, which in turn divide into the five major branches: the temporal, zygomatic, buccal, marginal mandibular, and cervical branches (Figure 1.7a). In reality, the temporal and marginal mandibular branches are single terminal rami in about 85% of the population; the other branches cross-arborize and have multiple rami, making the muscles by these latter nerves less prone to permanent paresis. Obviously, the former are at greater risk for lasting damage if severed or injured during surgery.

Figure 1.7 (a) Motor nerves. (b) Temporal nerve depth. (c) Marginal mandible nerve damage.

Temporal Nerve

The temporal nerve can be roughly projected onto the skin from a line connecting a point 0.5 cm below the tragus of the ear to a point 2 cm above the lateral eyebrow where it innervates the frontalis muscle. Some fibers go to the upper orbicularis muscle. Like the other branches, it is protected in its initial course by the parotid gland through which it runs. It is most vulnerable at the zygomatic arch and the temple where it resides deep in superficial temporal fascia (Figure 1.7b). Remember that the neurovascular bundle containing the sensory auriculotemporal nerve and superficial temporalis artery and vein are more superficial in the lower subcutaneous fat above the superficial temporal fascia. The temporal nerve is most vulnerable during extirpative surgery involving invasive or recurrent skin tumors that frequently occur in this area. Imprecise undermining in the wrong plane may also damage the nerve. It is prudent to recognize that motor nerves, as myelinated nerves, are also subject to the effects of local anesthesia and repeat injections, as may occur in Mohs micrographic surgery, can cause deep, long-lasting nerve blocks. This can cause the unwary surgeon and the patient needless concern for the 10 or more hours it takes nerve function to return. In general, if the surgery has exposed a fascial plane that moves easily in a side-to-side manner to the probing (gloved) finger, it is the superficial temporal fascia and the temporal nerve is probably intact. If the tissue is an immovable, tightly bound-down glistening membrane, the temporal fascia over the temporal muscle of mastication has been reached and the nerve has probably been cut.

Damage to the temporal nerve results in paresis of the frontalis with an ipsilateral inability to wrinkle the forehead or open the eye widely. The asymmetry is discomforting, but functional upper visual field problems may ensue if the resulting brow ptosis is compounded by significant dermatochalasis of the upper lid skin.

Zygomatic and Buccal Nerves

The zygomatic nerve divides into many arborizing rami after leaving the parotid gland and has interconnections with branches of the buccal nerve. It primarily innervates the orbicularis oculi muscle but also the corrugator supercilii and procerus muscles and upper fibers of the levator labii superioris complex. The buccal nerve shares connections with the zygomatic nerve, but primarily innervates the levator labii superioris, levator labii superioris alaeque nasi, buccinator, zygomaticus major and minor, levator anguli oris, and orbicularis oris muscles.

Marginal Mandibular and Cervical Nerves

The marginal mandibular nerve, like the temporal branch, is most often a solitary ramus after leaving the parotid gland. It innervates the lip depressors, the risorius muscle, and the mentalis muscles. It is particularly prone to injury because it is relatively superficial and covered by only a variable platysma muscle at the jaw line at the anterior border of the masseter muscle. It may be at, above, or below the jaw line between its exit from the parotid and the anterior border of the masseter muscle. Skin cancers as well as deep acne scars occur frequently in these locations, making surgery dangerous for the unwary. Injury to the nerve results in an inability to retract or depress the corner of the mouth when smiling. The unopposed pull from the unaffected side cause the damaged-side lower lip to flatten and rotate inward upon smiling (Figure 1.7c).

The cervical branch innervates the platysma muscle and is rarely a clinical consideration.

Trigeminal Nerve (Cranial V)

As the nerve of the embryonic first branchial arch, the trigeminal nerve supplies motor fibers to the muscles of mastication, secretory fibers to the lacrimal, parotid, and mucosal glands, and sensory innervation to the face and anterior scalp. It has three main sensory branches originating from the middle cranial fossa-situated trigeminal or gasserian ganglion that divide the face and scalp both horizontally and vertically (see Figures 1.8a and b). These nerve divisions have been classically designated as the ophthalmic (V1), maxillary (V2), and mandibular (V3) nerves.

Figure 1.8 Sensory nerves. (a) Deep to superficial pathways. (b) Cutaneous innervation.

External Carotid System

The external carotid system is the main blood supply to the lower face, temple and posterior scalp.

The main branch of the external carotid artery to the central face, the facial artery, enters onto the face after exiting the submandibular gland at the anterior border of the masseter muscle at the jaw line (Figure 1.9). It runs obliquely superior within the substance of the lip depressor muscle complex toward the commissure of the lip. Within the substance of the orbicularis oris muscle, it first gives off the inferior labial artery that runs medially through the lower lip to meet its pair from the other side. Next, at the level of the upper lip, the similarly disposed superior labial artery is given off and runs transversely through the upper lip to meet its contralateral partner.

After giving off the superior labial artery, the facial artery becomes known as the angular artery as it makes its way up toward the alar base and consequently upward alongside the nose to anastomose with the dorsal nasal artery, a branch of the ophthalmic artery of the internal carotid system. This anastamotic complex at the medial canthal level is an important vascular pedicle for the dorsal nasal or Rieger flap.

Other main branches off the external carotid include the occipital artery that courses posteriorly and superiorly in company with the sensory occipital nerve between the trapezius and sternocleidomastoid muscles to run just above the occipital muscle to supply the posterior scalp. The postauricular artery arches around the styloid process to a groove between the mastoid process and the external ear to supply the posterior ear and portions of the adjacent scalp above and behind the ear.

After giving off the facial and occipital arteries, the external carotid artery divides into its two terminal branches, the superficial temporal artery and the internal maxillary artery. The latter branch is primary internal to the mouth and nose, but after several divisions does supply terminal vessels that exit the infraorbital and mental foramen as same-named arteries along with their respective veins and sensory nerves. They provide important anastomoses with the facial artery.

The more important division to dermatologic surgeons is the superficial temporal artery. This runs superiorly in front of the ear within the substance of the parotid gland along with the same-named vein and the auriculotemporal nerve, a sensory branch of the mandibular nerve of the trigeminal (Vth cranial) nerve. As the neurovascular bundle exits the superior pole of the parotid gland, the artery is palpable at the level of the superior attachment of the ear. At this point, it splits into anterior and parietal branches to supply the temple/lateral forehead and parietal scalp, respectively.

Internal Carotid System

The main volume of blood from the internal carotid system is dedicated to supplying the brain. A portion is allotted to the face, predominantly to the ophthalmic artery whose terminal branches exit the skull as the supraorbital and supratrochlear arteries as part of the same-named neurovascular bundles (Figure 1.9). They exit their respective foramen and pierce the overlying frontalis muscle to run superiorly. At this point, they are displaced deep in the subcutaneous fat above the frontalis fascia and subsequently over the galea aponeurotica as they course superiorly over the scalp. They supply the forehead and anterior scalp (see Figure 1.9). As noted earlier, the supratrochlear artery is recruited for the classic and extremely useful axial mid-line forehead flap. Both arteries partake in the rich anastomotic network over the scalp by connecting with branches of the superficial temporalis and occipital arteries. So powerful is this network that traumatic scalping can be repaired by vascular reconnection of even one of these major vessels that supply the scalp.

The other major branch off the ophthalmic artery is the dorsal nasal branch (in some references, noted as the infratrochlear artery) at the medial canthus. It runs inferiorly along the side of the nose in the medial canthal region to supply the bridge of the nose and to connect with angular artery of the external carotid system.

It is interesting that above the zygomatic arch, the neurovascular bundles containing the major arteries and veins all course in the deep subcutaneous plane above the fascia or muscles of facial expression. Conversely, below the arch, the vessels are usually within the substance of the mimetic muscles and do not course in the company of the major sensory nerves. Knowledge of the route and depth of the vessels will aid in not severing them unintentionally during a procedure in the region. On the other hand, when they have to be cut, as in a lip wedge excision, knowing that the labial artery is located in the very posterior portion of the distal orbicularis oris allows the surgeon to locate and clamp it off immediately before it retracts into the substance of the muscle.

Venous System

The vascular drainage of the face for the most part parallels the arterial supply. Generally, the veins have a straighter, less tortuous path than their counterpart arteries.

Lymphatic System

The advent and widespread use of lymphoscintigraphy has at once confirmed and expanded much of what we know about the lymphatics of the head. The system is certainly much more variable than once believed. The impetus for this interest is that melanoma, squamous cell carcinoma, and Merkel cell carcinoma all tend to metastasize first to primary echelon nodes, and a complete examination for these tumors includes evaluation of the draining lymph nodes either by manual palpation or by histopathologic evaluation following sentinel lymph node biopsy. Some generalities apply to the lymphatic system of the head and neck.

First, the central face and scalp are usually devoid of lymph nodes except for a few inconsistent, ectopic nodes found above the mimetic muscles in the subcutaneous fat. Generally, they are encountered by accident during surgery or found in the pathology specimen.

Next, afferent drainage is organized in flow patterns that proceed in a superior to inferior, diagonal direction toward the collecting, primary echelon nodes in the upper neck region. These include the submental, submandibular, jugulodigastric, and occipital lymph nodes (Figure 1.10). Drainage from these superficial nodes then proceeds to the deeper cervical systems in the neck (the spinal accessory, internal jugular, and transverse cervical lymph node basins).

Figure 1.10 Lymphatic drainage of the head and neck.

The real wild cards in the system are the lymph nodes within the substance of the parotid gland. These nodes are difficult to clinically assess and even lymphoscintigraphy may prove difficult because of the proximity of the tumor to the parotid gland. They drain a wide area including portions of the anterior scalp, forehead, lateral eyelids, cheeks, nose, and upper lip. Subsequent drainage is to the deeper neck node basins.

Lip

The lips are the guardians of the oral seal that is required for phonation and mastication. On a social level, the marvelously expressive lips convey our nonverbal communication. As such, they are at once the least complicated and the most mobile of the special structures of the face. The two are related; by not having a constricting solid structure such as the bony/cartilaginous frame of the nose or the form-shaping tarsal plate of the eyelid, the lips are quite flexible, stretchable, and elastic. The lips having only a very thin subcutaneous fat layer in the cutaneous portion also facilitate this ability.

Internally, they consist solely of the orbicularis oris muscle and the myriad muscular insertions attached to it. They are covered on the outside by skin, on the inside by a wet mucosa and at the vermilion by a dry modified mucosa (Figure 1.11). The submucosa contains many salivary glands on the oral portion.

Figure 1.11 (a) Structures of the lip. (b) Cross-section of the lip.

The lips may be divided into vermillion and cutaneous cosmetic units. The cutaneous upper lip is the most complicated section, having a small triangular portion that extends superior and lateral to the alar base and a central subunit, the philtrum. Two convex philtral crests (columns, ridges) define the mid-line concave philtral bowl. The lower portion of the latter is the beautiful downward curving Cupid’s bow. The philtrum is a reservoir of extra skin and interdigitating orbicularis muscle that allows for the dramatic stretching and vertical shortening of the upper lip when smiling or putting in dentures. In many people, the sharp cutaneous/vermilion junction line has a superimposed white roll. This 1- to 2-mm, glabrous strip of skin is due to an anterior bulging of the orbicularis oris muscle. It can be quite prominent in some people and can be an important consideration in placing transverse scar lines.

Nose

The nose is an extremely complex, esthetically and functionally important mid-line structure that is all too often the site of an invasive skin cancer. It is supported by a bony/cartilaginous infrastructure that features the inflexible paired nasal bones superiorly and the highly mobile paired upper lateral/alar cartilage complex inferiorly (Figure 1.12). Conversely, the skin over the rigid bony upper portion is highly movable, while the skin over the mobile cartilage portion is thick, sebaceous and bound down.

Figure 1.12 Structures of the nose.

On the surface, the nose can be broken down into several cosmetic subunits. These include the root of the nose that extends from medial canthus to medial canthus. The skin lines in this concave unit run transversely across it. Obliteration of the concave nature of this area during repairs causes the profile to be dramatically altered and the nose to appear very large on the frontal view. The paired lateral sidewalls separate the nose from the cheek and are in turn separated from each other by the midline dorsum of the nose unit. The heart-shaped convex tip of the nose is the most prominent feature of the nose and is bounded by the paired alae nasi. The columella is the midline structure below the tip separating the nostril apertures and culminating in the upper philtrum of the lip. The RSTL of the upper nose run obliquely out from the medial canthus down the dorsum and lateral sidewall. They end part way down as there are no skin lines on the lower nose. As noted earlier they run transversely across the root.

The lower nose is supported by the paired, upper lateral cartilages, which act as extensions of paired nasal bones. The paired, lower lateral or alar cartilages begin as medial crura that form the columella. As they swing back and curve they form an arch that is the tip of the nose. As the lateral crura diverge obliquely upward and laterally away from the midline vertical nasal septum cartilage, they support the ala nasi. It is important to recognize that the ala nasi are composed of fibro-fatty muscular tissue and are really devoid of cartilage. Their ability to flare (and not collapse) with each inspiration is due to the involuntary contraction of the levator labii superioris alaeque nasi and nasalis muscles. If these latter muscles have been removed during tumor extirpation, then a cartilage strut must be included in the surgical repair or the nostril will collapse during inspiration.

The upper portion of the nose is innervated by the infratrochlear (V1) of the trigeminal, whereas the anterior branch of the external ethmoid nerve (also V1) supplies the tip. The lateral portions of the nose are innervated by the infraorbital nerve (V2).

Eyelids

The eyelid is easily the most complicated structure on the face and of extreme functional importance. Successful repair of the unique structures that compose the eyelids are contingent on thorough knowledge of the anatomy as it is so closely related to function. The eyelids guard the globe and orbit and are structured on the orbicularis oculi muscle, whose orbital and palpebral components have been discussed earlier in this chapter. As noted, the orbicularis is responsible for closing the lid. The levator palpebrae superioris muscle and aponeurosis is responsible for opening the eye (Figure 1.13a). It is innervated by the oculomotor or third cranial nerve. It arises from the superior orbit and divides into two components: Muller’s muscle, which attaches into the superior margin of the tarsal plate under sympathetic nerve control, and the levator aponeurosis, which fuses with the orbital septum to form the superior palpebral fold about 10 mm above the lid margin and then continues downward to attach to the anterior surface of the tarsal plate. It also sends fibers through the pretarsal orbicularis to insert into the lid skin. This is why the skin in the pretarsal area is bound down, whereas it is loose and eventually redundant in the preseptal area above the superior palpebral fold. The space between the orbital septum and the levator aponeurosis contains the orbital fat pads. The skin of the eyelids is the thinnest and most elastic in the body. It contains little subcutaneous fat.

Figure 1.13 (a) Structures of the eyelid. (b) Lacrimal apparatus.

The posterior portion of the eyelid closest to the globe contains the tarsal plate that consists of dense fibrous tissue. They give form to the lids and also contain the sebaceous Meibomian glands. The conjunctiva covers the posterior eyelids as well as the globe. Hair follicles of the eyelashes (cilia) with both sebaceous glands (Zeis) and sweat glands (Moll) exit onto the lid margin below the muscular layer while the Meibomian glands exit onto the lid closer to the conjunctival surface.

The lacrimal system is important to eye homeostasis. (Figure 15b). The lacrimal gland is situated in the postseptal space lateral to the fat pads. The lacrimal collecting system consists of the upper and lower lacrimal puncta at the medial eyelid margins, which open into the lacrimal canaliculi at the medial margin of the tarsi. The upper and lower canaliculi converge under the medial canthal tendon as the common canaliculus to run horizontally into the nasolacrimal duct on the side of the nose opposite the medial canthus and drains as the nasolacrimal canal into the nose beneath the inferior turbinate.

Ear

The ear appendage is essentially skin stretched over a rather intricately molded cartilage infrastructure. Its dermatological surgical importance is as a high risk for both BCC recurrences and even more critical as high-risk site for invasive squamous cell carcinoma. Invasive SCC tumors of the helical rim tend to reach the larger lymphatic and venular vessels of perichondrium at a shallower depth than elsewhere on the body, making metastases from this area a real threat.

The outer rim of the ear is the convex helix that extends upward from the lobule to curve around and ending as the crus of the helix that divides the concha bowl into the upper cymba and the lower cavum (Figure 1.14). Opposite the cavum and guarding the external auditory meatus is the small protuberance, the tragus. Also superior to the lobule is the convex antihelix. This structure parallels the helix in its vertical dimension and is separated from it by the depression between them, the scapha. The antihelix splits at its superior end into two crura to form a central concavity, the triangular fossa. Only the lobule is not supported by cartilage.

Figure 1.14 Structure of the ear.

The sensory innervation of the ear is complicated. The anterior surface closest to the cheek as well as the anterior-superior portion of the external auditory canal is supplied by branches of the auriculotemporal branch of the mandibular division (V3) of the trigeminal nerve. The lower posterior surface as well as the lower anterior helical portion is innervated by the great auricular nerve (C2, 3) while the upper posterior portion and the upper vertical portion of the anterior helical area are supplied by the lesser occipital nerve (C2, 3). Variable contributions of the cranial nerves IX and X supply the remaining portions of the external auditory canal. Understanding this innervation pattern is required for regional nerve block of the ear.