Nasal fat pad Preaponeurotic fat pad Lacrimal gland

Temporal fat pad

Central fat pad

Nasal fat pad

Buccal fat pad

Masseter M.

Buccinator M.

Fig. 30.12 Deep fatty structures of the face

individual. It is most prominent over the temples, concavities of the cheeks, and the neck region and negligible over the eyelid and post-auricular region [1, 16].

The deeper fatty layers of the face include the buccal fat pad as well as the sub-orbicularis oculi and retro-orbicularis oculi fat. This tissue runs deep to the SMAS and is comprised of more loosely arranged fat, lacking the distinct fibrous septae of the superficial fat. Loss of deep facial fat with aging is thought to lead to alteration in facial shape and contour [16]. The buccal fat pad overlies the posterolateral portion of the maxillary bone lateral to the buccinator muscle. It functions to provide volume to the cheek as well as augment the actions of the muscles of mastication by acting as a smooth gliding surface. The deep fatty layers of the orbit are separated from the anterior portion of the eyelid by the orbital septum. This septum atrophies with age, leading to anterior displacement and “pseudoherniation” of fat pads within the orbit. The superior orbit contains two distinct fat pads, the nasal and preaponeurotic fat pads, and the lacrimal gland occupies the lateralmost compartment. Inferiorly, there are three separate fat pads including the nasal, central, and temporal fat pads (Fig. 30.12). Each structure is separated by a thin layer of fascia. Care must be taken to distinguish the lacrimal gland at the lateral aspect of the

superior orbit as this may be confused with fatty tissue [5, 15, 16, 17].

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 [18, 19]. The SMAS extends superiorly from the platysma to the temporalis and frontalis muscles and from the orbicularis oculi muscle to the trapezius muscle posteriorly [6, 20]. It becomes thin and discontinuous in the central face and develops a thicker, inelastic consistency in areas without underlying musculature, forming the superficial temporalis fascia and galea aponeurotica. Sensory nerves and axial arteries typically lie within the SMAS whereas motor nerves travel deep to this layer. The deep fascia of the face is derived from the deep cervical fascia. It forms a continuous immobile layer consisting of periosteum, perichondrium, and the investing fascia of the muscles of mastication [13].

Summary: Bony and Cartilaginous Structures

of the Face and Scalp

•The structure of the face is largely determined by the underlying bony structures which serve as important anatomic landmarks.

•The structure and functional support of the nose is provided by its bony and cartilaginous skeleton. The superior one-third of the nose consists of two paired nasal bones whereas the structural support for the distal portion of the nose is comprised of cartilage and fibrofatty tissue.

•With the exception of the earlobe, which does not contain cartilage, the structure of the auricle is created by a single fragment of elastic cartilage.

30.5Bony and Cartilaginous Structures of the Face and Scalp

30.5.1 Bony Landmarks

The shape of the face is largely determined by the underlying bony structures (Fig. 30.13). These structures may also serve as important landmarks, and

knowledge of the bony topography is invaluable to the cutaneous surgeon. The external calvarium is comprised of the frontal, sphenoid, parietal, and occipital bones which are separated by cranial sutures. These bones, with the exception of the sphenoid, dictate the nomenclature by which the various regions of overlying scalp are referred. The occipital bone possesses a medial prominence termed the occipital protuberance. Lateral to this structure are two ridges termed the highest and superior nuchal lines. The highest nuchal line serves as the bony attachment of the occipitofrontalis muscle. The frontal and parietal bones possess two slightly elevated ridges called the inferior and superior temporal lines. These prominences serve as the superior attachment points for the temporalis muscle and temporalis fascia, respectively, which overly the temporal fossa. The mastoid process is the inferiormost portion of the temporal bone, and it protects the facial nerve as it emerges from the skull. It also serves as an attachment point for the occipitalis muscle [1, 4].

The frontal bone comprises the forehead and anterior scalp. Inferiorly, it also forms the orbital roof and supraorbital margin. The supraciliary arches are rounded prominences deep to the eyebrows which meet centrally to form the glabella. Inferiorly to these prominences lies the superior orbital rim which terminates laterally at the zygomatic process. The supraorbital notch may be palpated along the superior orbital rim, approximately 2.5 cm from the midline [20]. The lateral orbit is formed by the zygomatic process of the frontal bone and the frontal process of the zygomatic

bone. Medially, the orbital rim is formed by the maxillary process of the frontal bone, the frontal process of the maxillary bone, and the lacrimal bone. A fossa formed by the lacrimal and maxillary bones houses the lacrimal sac. Much of the infraorbital margin and the orbital floor are comprised of the maxillary bone [20].

The maxillary bone also forms the upper jaw, lateral nasal sidewall, and the roof of the mouth. It is further subdivided into the body as well as the zygomatic, frontal, alveolar, and palatine processes. Anteriorly, the body of the maxilla houses the infraorbital foramen. The zygomatic process forms the medial cheekbone and connects laterally to the zygomatic bone. The zygomatic bone forms the zygomatic arch and lateral cheekbone as well as a portion of the lateral orbital rim and orbital floor. The frontal process of the maxilla contributes to the lateral nasal sidewall and the medial orbital rim. The alveolar process houses the upper teeth, and the palatine process comprises the hard palate [20].

The mandible constitutes the chin and jawbones and is the only mobile bone of the skull. It is made up of a body which houses the lower teeth and is connected by the angle of the mandible to a posterior ramus. The posterior ramus gives off the anterior, coronoid, and posterior condylar processes. The condylar process serves as a point of articulation of the mandible with the temporal bone. The mandible fuses centrally at the mandibular symphysis. The mental foramen is typically situated lateral to the midline, and inferior to the first and second premolars [20]. The masseter muscle attaches to the inferior aspect of the mandibular

Fig. 30.14 Bony and cartilaginous structures of the nose

ramus. Anterior to the masseter, there is a shallow groove that houses the facial artery, which should be palpable at this point.

30.5.2 Cartilaginous Structures

The structure and functional support of the nose is provided by its bony and cartilaginous skeleton (Fig. 30.14). The superior one-third of the nose consists of two paired nasal bones that articulate proximally with the nasal processes of the frontal bone, laterally with the maxillary frontal processes, and inferiorly with the ethmoid bone which also forms the perpendicular plate of the nose. The perpendicular plate of the ethmoid, along with contributions from the vomer, forms the bony septum which articulates with the cartilaginous septum

distally [20]. The pyriform aperture, or the opening of the nose into the skull, is formed superiorly by the nasal bones and inferolaterally by the maxilla. The proximal portions of the nasal bones are thicker, becoming progressively thin and more prone to fracture as they approach the nasal cartilage. The middle one-third of the nose consists of the paired upper and lower lateral cartilages which are continuous with one another and the septal cartilage. Proximally, lateral nasal cartilage overlaps and articulates with the nasal bone via ligamentous attachments. Laterally and distally, these cartilages connect to the nasal ala via fibrofatty tissue. The cartilaginous nasal septum is fused dorsally to the lateral cartilages with the exception of its distal portion, the septal angle, which contributes to the columella. The lobule is the most distal, mobile portion of the nose and derives its structural support from the lower lateral cartilages. The medial crura of the lower lateral cartilages comprise the columella, while the lateral crura provide structural support to the nasal ala. The point where the crura meet one another is termed the dome which forms the nasal tip. Although the lateral crura provide structural support for the nasal ala, the majority of the ala is composed of dense fibrofatty tissue without a cartilaginous component [20, 21].

With the exception of the earlobe which does not contain cartilage, the structure of the auricle is created by a single fragment of elastic cartilage (Fig. 30.15). The conchal cartilage abuts the mastoid bone, anchoring the auricle to the skull. This cartilaginous network extends to the distal portion of the external auditory meatus formed by the temporal bone [5].

Summary: Muscosa of the Lip, Nose,

and Conjunctiva

•It is important to close each tissue layer of the lip individually in full-thickness defects to maintain proper lip function and to prevent dead space formation.

•The eyelid is divided into an anterior lamellar division comprised of skin and orbicularis muscle and a posterior lamellar division comprised of the tarsal plate, orbital septum, and conjunctival mucosa.

30.6Muscosa of the Lip, Nose, and Conjunctiva

The cutaneous lip is divided from the vermilion lip by the white roll, a soft tissue prominence augmented by the underlying orbicularis oris muscle. At this point, there is a conversion to a dry mucosal surface, lacking normal keratinization, follicular units, or glandular tissue. Posteriorly, the vermilion lip then transitions to form a wet mucosal surface or buccal mucosa (Fig. 30.16). It is important to close each tissue layer (skin, muscle, mucosa) individually in full-thickness lip defects to maintain proper lip function and to prevent dead space formation [4, 14].

The anterior inner naris is comprised of the vestibule lined by modified squamous epithelium. The vestibule possesses many small hairs termed vibrissae which function to filter dust and debris, inhibiting entry into the respiratory tract. Posterior to the vestibule, the inner naris becomes the nasal cavity proper, and there is a transition from stratified squamous epithelium to ciliated pseudostratified columnar epithelium. The superior, middle, and inferior nasal turbinates, ensheathed by a layer of periosteum and overlying highly vascularized epithelium, are attached to the lateral walls of the nasal cavity. The superior, middle, and inferior meatuses are crevices which run below their respective turbinates (Fig. 30.17) [22].

The eyelid is typically divided into an anterior lamellar division comprised of skin and orbicularis muscle and a posterior lamellar division made up of the tarsal plate, orbital septum, and conjunctival mucosa (Fig. 30.18). These lamellae are partitioned by a layer of

Labial artery

Cutaneous lip

Salivary

glands Obicularis oris muscle

Skin and subcutaneous tissue

Fig. 30.16 Cross-sectional anatomy of the lip

fascia, also termed the gray line, at the lid margin. The tarsi are thick collections of fibrous tissue important for lid structure and stability. These structures also house the Meibomian (sebaceous) glands. The conjunctiva is a thin layer of mucosa that spans from the posterior aspect of the lid and is reflected inferiorly at the fornix to adhere to the anterior surface of the globe [4, 11].

Summary: Musculature, Innervation,

and Bony Structures of the Neck

•The sternocleidomastoid muscle is an important anatomic landmark of the neck. It divides the neck into anterior and posterior triangles, functions to flex the neck and rotate the head contralaterally, and is innervated by the spinal accessory nerve (cranial nerve 11).

•The anterior triangle of the neck may be subdivided into the submental, submandibular, carotid, and muscular triangles.

•The spinal accessory nerve is especially susceptible to injury within the posterior triangle. Injury to this nerve leads to difficulty abducting the arm, chronic shoulder pain, and difficulty shrugging the shoulders.

Fig. 30.17 Nasal mucosal anatomy

Superior nasal turbinate

Superior meatus

Middle nasal turbinate

Middle meatus

Inferior nasal turbinate

Inferior meatus

Nasal vestibule

Orbicularis oculi muscle

Orbital septum

Levator aponeurosis

Superior tarsal plate

Meibomian gland

Inferior tarsal plate

Conjunctiva

Fat

Skin

Fig. 30.18 Cross-sectional anatomy of the eyelid

30.7Musculature, Innervation,

and Bony Structures of the Neck

The neck is bounded by the clavicle and sternum inferiorly and the mandible superiorly. The hyoid bone is located just inferiorly to the mandible at the midline if the anterior neck. The thyroid cartilage, cricoid cartilage, and tracheal rings, respectively, rest below the hyoid bone. Posteriorly, the cervical vertebrae provide stability to the neck [22].

The platysma, as discussed previously, is considered a muscle of facial expression. It originates in the

superficial fascia of the upper chest, covering the neck and extending over the body of the mandible to intercalate with the muscles of the lower lip. It is ensheathed by a layer of superficial fascia that is continuous with the SMAS and innervated by the cervical division of the facial nerve. There are also layers of deep cervical fascia which cover the superficial and deep muscles of the neck, brachial plexus, and laryngotracheal structures. The sternocleidomastoid muscle is an important anatomic landmark of the neck. It has two heads that attach inferiorly to the sternum and medial clavicle and travel obliquely to insert at the mastoid process of the temporal bone and lateral to the superior nuchal line of the occipital bone, respectively. This muscle divides the neck into anterior and posterior triangles, functions to flex the neck and rotate the head contralaterally, and is innervated by the spinal accessory nerve (cranial nerve 11) [4, 22].

The anterior triangle of the neck is bordered posteriorly by the sternocleidomastoid muscle, which spans from the mastoid process to the sternum, superiorly by a line extending from the mastoid process along the base of the mandible to the anterior chin, and medially by a line extending from the chin to the jugular notch. It is further subdivided into submental, submandibular, carotid, and muscular triangles (Fig. 30.19). Particular areas of concern within the anterior triangle include the facial artery within the submandibular triangle. The internal and external carotid arteries, the internal jugular vein, and the vagus nerve travel within the carotid sheath in the carotid triangle and are protected