Chapter 2 Anatomy of the Face
According to some studies, the subcutaneous tissue of the face is not homogeneous, and is divided into numerous different anatomical units called fat pads. These in turn are classified as superficial and deep (Fig. 2.1–2.13). They are separated by very thin fibrous septa that are, in fact, simply projections of the superficial muscular aponeurotic system (SMAS).a Changes in volume and position of these fat pads over the years are at least partially responsible for aging of the face: In a young face, the transition between these pads is smooth, whereas aging causes an abrupt change in the contour of these regions. Consequently, understanding this anatomy makes it possible to achieve better precision, efficacy, and safety when treating patients 1 ,. 2 (Fig. 2.14–2.16).
Periorbital Fat Pads
Superficial Fat Pads
The literature describes three superficial fat pads (SFPs) around the eyes: superior, inferior, and lateral. The first two are delimited externally by the orbicularis retaining ligament and are under the skin of the upper and lower eyelids, respectively. The inferior fat pad is so thin that it cannot always be found when dissecting fresh cadavers. The top of the lateral fat pad is delimited by the inferior temp or al septum and the bottom by the superior malar septum (Fig. 2.17 and2.18). 3
Deep Fat Pads
The orbit is the base of the periorbital complex and is formed by the frontal and zygomatic bones, and the maxilla. It has a cone -like structure that holds the eyeball, the intraocular muscles, and the orbital fat, which principally lubricates and cushions the eyeball and intraocular muscles. Inferior orbital fat is divided into three pads—nasal, central, and lateral—which are restrained by the orbital septum that extends from the tarsus to the inferior orbital rim. Protrusion of this fat translates clinically as “fat bags” (Fig. 2.19 and2.20).
The palpebral portion of the orbicularis oculi muscle covers the orbital septum, and inserts distally in the inferior orbital rim. The orbital portion of this muscle originates below the palpebral portion, 0.5 to 1 cm below the inferior orbital rim. It is covered by the nasolabial and superficial medial cheek fat pads and rests laterally over the suborbicularis oculi fat (SOOF), also known as prezygomatic fat. The SOOF is didactically divided into medial and lateral portions (Fig. 2.21 and2.22).
Retroorbicularis oculi fat (ROOF) is the fat pad located deep to the orbicularis oculi muscle, which originates medially at the level of the supraorbital nerve and extends laterally over the superior orbital rim (Fig. 2.4 and2.19).
Fat Pads of the Middle Third of the Face
The fat in the middle third of the face includes a superficial and a deep portion. The superficial portion comprises the nasolabial, medial cheek, and middle cheek fat pads, as shown inFig. 2.23 and2.24. The deep portion comprises the medial and lateral cheek fat pads and the SOOF, also called prezygomatic fat (Fig. 2.21 and2.22). The SMAS lies between the superficial and the deep portions, encompassing the levator muscles of the upper lip and ala of the nose, the upper lip, the minor and major zygomatics, and the vessels and nerves (Fig. 2.25–2.27). 4
Temporolateral Fat Pad
This fat pad extends from the temporal to the cervical region. The temporal region is below the skin and above the superficial temporal fascia of the temporal muscle (Fig. 2.1–2.39). 4 The upper part of this region is delimited by the temporal line (prominence of the frontal bone); the lower part is delimited by the zygomatic arch; the anterior part is delimited by the external orbital rim; and the posterior part is delimited by the scalp. The superficial temporal artery is in the posterior region of this fat pad. The distal portion covers the mandibular angle and the mandibular line, resting over the parotid gland and the mandibular body (Fig. 2.28 and2.29).
This fat pad gives a “bulldog” appearance to the lower third of the face, and is located above the inferior rim of the mandibular body. It is delimited medially by the depressor muscle of the angle of the mouth (DMAM); the upper part is delimited by the nasolabial and medial cheek fat pads, the lower part by the platysma muscle, and the posterior part by the facial pedicle. It is divided into superficial and deep fat pads (Fig. 2.30 and2.31). 5
Fat Pad of the Lips
The lips are formed by an internal portion, thelabial mucosa (nonkeratinized stratified squamous epithelium and chorion rich in blood vessels and minor or accessory salivary glands), by a transition region, thevermilion border (keratinized stratified squamous epithelium without hair follicles, apocrine or salivary glands, and possibly sebaceous glands), and by an external portion comprising the skin and its appendages. The internal portion is moist, while the others are dry. The muscle fibers of the orbicularis oris muscle insert into the border between the internal portion, thelabial mucosa, and the transition area, thevermilion border. The orbicularis oris muscle delimits two compartments:
Buccal Fat Pad (Bichat’s Fat Pad)
The buccal fat pad, also called Bichat’s fat pad, was first described in 1732 by Heister, who thought this tissue had a glandular origin. However, Marie François Xavier Bichat, a French anatomist and physiologist, was the one who, in 1802, recognized it as a fat pad. Bichat’s fat pad is directly related to the chewing muscles and, in childhood, it helps in sucking and confers a cherubic look.
It is a deep fat pad in the center of the submalar triangle. It has a triangular shape, with extensions between the masseter, temporal, and pterygoid muscles, and rests over a fissure above the buccinator muscle and below the SMAS. The facial artery and vein are located anteriorly to Bichat’s fat pad. The transverse facial vessels supply to its superior portion, above the parotid duct, and branches of the internal maxillary artery also contribute to vascularization.
The external carotid artery divides into an average of eight branches that supply the face and structures of the neck. These are: the superior thyroid artery, ascending pharyngeal artery, lingual artery, facial artery, occipital artery, posterior auricular artery, superficial temporal artery, and maxillary artery. The internal carotid artery does not divide into branches until it enters the cranium.
After joining the facial vein, the facial artery becomes more superficial, passes over the inferior edge of the mandible at the level of the anterior rim of the masseter, and then penetrates the face (Fig. 2.40–2.44 andFig. 2.57). The inferior labial artery originates close to the oral commissure; it branches anteriorly under the depressor muscle of the angle of the mouth and, crossing the orbicularis oris muscle, presents a tortuous path along the edge of the lower lip, between this muscle and the mucous membrane. The inferior labial artery anastomoses with the contralateral artery. The superior labial artery is larger and its overall path is more tortuous than the inferior one; it follows the same course along the edge of the upper lip, lying between the mucous membrane and the orbicularis oris muscle, as shown inFig. 2.40,2.41,2.43–2.48,2.55,2.56, andFig. 2.58–2.62. The superior labial artery also anastomoses with the contralateral artery and divides into a septal branch, which supplies the nasal septum, and an alar branch, which supplies the ala of the nose. After dividing into these two branches, the facial artery continues its ascending course and divides into the lateral nasal branch. This supplies the ala and nasal dorsum, and anastomoses on the contralateral side with the septal and alar branches, the dorsal nasal branch of the ophthalmic artery, and the infraorbital branch of the maxillary artery (Fig. 2.40,2.41, andFig. 2.43–2.45). The angular artery is the terminal part of the facial artery (Fig. 2.40,2.41,2.43,2.44,2.45, andFig. 2.47–2.52); it ascends in the direction of the medial angle of the orbit in the midst of the fibers of the levator muscle of the upper lip and the ala of the nose, accompanied by the angular vein more laterally. The branches of the angular artery anastomose with the infraorbital artery and then, after supplying the lacrimal sac and the orbicularis oculi muscle, anastomose with the dorsal nasal branch of the ophthalmic artery (Fig. 2.40,2.41,2.43,2.44,2.45,2.47,2.48–2.50, andFig. 2.53). 7
The superficial temporal artery, the smaller of the two terminal branches of the external carotid, is a continuation of this vessel. It has its origin inside the parotid gland, posteriorly to the neck of the mandible. Passing over the posterior root of the zy-gomatic process of the temporal bone, it divides into the frontal and parietal branches, approximately 5 cm above it. Above the zygomatic process and in front of the auricular pavilion, the superficial temporal artery is shallow, and its pulse can be easily felt. The transverse artery of the face also originates in the parotid gland. It lies between the parotid duct and the inferior rim of the zygomatic arch. The transverse artery supplies the parotid gland, parotid duct, and masseter muscle. The zygomaticoorbital artery flows along the upper edge of the zygomatic arch, in the direction of the lateral angle of the orbit. It supplies the orbicularis oculi muscle, and anastomoses with the lacrimal and palpebral branches of the ophthalmic artery. The frontal branch flows in the direction of the forehead, and anastomoses with the supraorbital and frontal arteries. The parietal branch runs superiorly and posteriorly, lying superficially to the temporal fascia and anastomosing with its homologous branches on the opposite side and with the posterior auricular artery and occipital artery (Fig. 2.40,2.41,2.43,2.44,2.46, andFig. 2.54). The maxillary artery, the larger of the terminal branches of the external carotid, originates behind the neck of the mandible, in the middle of the parotid gland tissue. It supplies the deep structures of the face and can be divided into the mandibular, pterygoid, and pterygopalatine portions. The two deep temporal branches (anterior and posterior), which are branches of the pterygoid portion, ascend between the temporal muscle and the pericranical muscle. The infraorbital artery is a branch of the pterygopalatine portion, and emerges from the cranium, together with the infraorbital nerve, through the infraorbital foramen (Fig. 2.41 and2.43).
The inferior alveolar artery is also a branch of the maxillary artery. It descends into the mandibular foramen, crosses the entire mandibular canal up to the mental foramen, where it divides into a large collateral branch, the mental artery, which supplies the soft tissues of the chin. The inferior alveolar artery continues between the trabecular bone until it anastomoses with the artery on the other side, in the medial plane.
The internal carotid artery divides into four segments: cervical, petrous, cavernous, and cerebral. The ophthalmic artery emerges from the cavernous segment and enters the orbit through the optic canal, inferiorly and laterally to the optic nerve. From there, it passes over the nerve to reach the medial wall of the orbit; it then continues horizontally along the inferior edge of the superior oblique muscle, dividing into two terminal branches: the supratrochlear artery and the dorsal nasal artery. The dorsal nasal artery emerges from the orbit above the medial palpebral ligament and, after branching to the upper part of the lacrimal sac, divides into two branches: one crosses the root of the nose and anastomoses with the angular artery; the other runs along the nasal dorsum, supplying its outer surface and anastomosing with the artery on the opposite side and with the lateral nasal branch of the facial artery. The supraorbital artery arises from the ophthalmic artery as that vessel crosses over the optic nerve. It courses superiorly and, together with the supraorbital nerve, between the periosteum and levator muscle of the upper eyelid, and passes through the supraorbital foramen to supply the skin, muscles, and pericranium of the forehead. It anastomoses with the supratrochlear, the frontal branch of the superficial temporal, and the artery of the opposite side (Fig. 2.40,2.41, andFig. 2.45). 7
Sensory and Motor Innervation
The trigeminal nerve is the great sensory nerve of the face and is the motor nerve for the muscles of mastication. Its first of five divisions is the ophthalmic nerve, which supplies the eyeball, conjunctiva, lacrimal gland, part of the mucous membrane of the nose and paranasal sinuses, skin of the forehead, eyelids, and nose. The frontal nerve is the main branch of the ophthalmic nerve and may be considered its continuation because of its size and direction. After entering the orbit, the ophthalmic nerve divides into the supraorbital and supratrochlear branches. The maxillary nerve, or second division of the trigeminal nerve, originates in the trigeminal ganglion; it is intermediate between the other two divisions in size and position, and like the ophthalmic, is entirely sensory. It supplies the skin of the middle portion of the face, lower eyelid, side of the nose, upper lip, mucous membrane of the nasopharynx, maxillary sinus, soft palate, tonsils and palate, and gums and upper teeth. In the segment behind the orbit, it becomes the infraorbital nerve and, continuing through the face, it enters the infraorbital canal. It emerges in the face through the infraorbital foramen, where it lies deep to the levator muscle of the upper lip and divides into branches for the skin of the face, nose, lower eyelid, and upper lip. The mandibular nerve, the third and largest division of the trigeminal, is a mixed nerve, with two roots: one large sensory root originating in the trigeminal ganglion and one small motor root. The sensory fibers supply the skin of the temporal region, outer ear, external auditory meatus, cheek, lower lip and inferior portion of the face, mucous membrane of the cheek, tongue and mastoid air cells, teeth and lower gums, mandible and temporomandibular joint, and part of the dura mater and the cranium. The motor fibers supply the muscles of mastication (masseter, temporal, pterygoid). The mandibular nerve has the following branches: meningeal nerve, medial pterygoid nerve, masseteric nerve, deep temporal nerves, lateral pterygoid nerve, buccal nerve, auriculotemporal nerve, lingual nerve, and inferior alveolar nerve. The mental nerve is the terminal branch of the inferior alveolar nerve. It emerges from the mandible into the mental foramen and divides into three branches below the depressor muscle of the angle of the mouth: one covers the skin of the chin and the other two the mucous membrane of the lower lip (Fig. 2.63–2.73). 7