Chapter 7The Head by Regions
The face is that part of the head visible in a frontal view, that is, all that is anterior to the external ears and all that lies between the hairline and the chin. Clustered in this region are the various facial openings and their associated sensory structures.
The facial region may be subdivided into a number of areas (Figure 7-1): (1) the forehead, extending from the eyebrows to the hairline; (2) the temples or temporal area anterior to the ears; (3) the orbital area containing the eye and covered by the eyelids; (4) the external nose; (5) the zygomatic (malar) area (prominence of the cheek); (6) the mouth and lips; (7) the cheeks; (8) the chin; and (9) the external ear.
The skin of the face is medium to thin in relative thickness. It is pliable and movable over a layer of loose areolar connective tissue except in the external ear and the ala of the nose, where the skin is fixed to underlying cartilage. Facial skin contains numerous sweat and sebaceous glands.
The superficial fascia or subcutaneous connective tissue contains variable amounts of fat that smooth out the contours of the face, particularly between the muscles of facial expression. In some areas the fat is extensive. The buccal (sucking) fat pad fills out the cheeks and extends upward to the scalp behind the bony orbit. Located within the subcutaneous tissue are facial vessels, sensory and motor nerves, and the superficial muscles of facial expression.
The facial cutaneous nerve supply is principally derived from the trigeminal nerve (cranial nerve V) (Figure 7-2). Within the skull, the trigeminal nerve divides into three parts: (1) the ophthalmic nerve (cranial nerve V-1), a sensory nerve associated mainly with the orbit and its contents; (2) the maxillary nerve (cranial nerve V-2), a sensory nerve associated with the nasomaxillary complex; and (3) the mandibular nerve (cranial nerve V-3), a sensory and motor nerve associated with the lower jaw and the muscles of mastication. Only the mandibular nerve contains motor as well as sensory fibers. Each division of the trigeminal nerve contributes sensory cutaneous branches to the face.
Figure 7-2 A, Cutaneous nerves of the face. V-1 (ophthalmic nerve): SO, Supraorbital nerve; ST, supratrochlear nerve; L, lacrimal nerve; IT, infratrochlear nerve; EN, external nasal nerve. V-2 (maxillary nerve): IO, Infraorbital nerve. V-3 (mandibular nerve): AT, Auriculotemporal nerve; B, buccal nerve; M, mental nerve. Spinal nerve: GA, Great auricular nerve. B, Motor nerves to the muscles of facial expression. Facial branches of CN VII: T, Temporal branches; Z, zygomatic branches; B, buccal branches; M, mandibular branches; C, cervical branches.
The supraorbital nerve emerges from the roof of the orbit through the supraorbital foramen, or notch. It travels to and supplies a small portion of the frontal sinus, a large portion of the upper eyelid, and a large portion of the forehead and scalp.
The supratrochlear nerve within the orbit passes over the pulley, or trochlea, of the superior oblique muscle. It emerges from the medial aspect of the superior orbital margin to supply the medial portion of the upper eyelid and adjacent forehead.
The infraorbital nerve is the large, terminal branch of the maxillary nerve. The infraorbital nerve passes through a bony canal in the orbital floor to emerge onto the face through the infraorbital foramen. On the face, it immediately breaks up into three sets of branches.
The zygomaticofacial nerve is a small branch of the zygomatic nerve, which, in turn, is a branch of the maxillary nerve. It emerges onto the face through the zygomaticofacial foramen to supply skin of the zygomatic prominence.
The auriculotemporal nerve surfaces between the temporomandibular joint and the tragus of the ear. It ascends to supply the skin of a portion of the external ear and ear canal, the temporal region, and the lateral aspect of the scalp.
The buccal branch of cranial nerve V-3 appears on the face from under the cover of the ramus of the mandible. It spreads over the cheek and conveys sensation from the skin and mucous membrane of the cheek. In addition, it conveys sensory information from the vestibular (buccal) gingiva of the mandibular molars.
Various facial branches of the trigeminal nerve are anesthetized following routine local anesthetic injections for dental procedures. Anesthesia of the mandibular teeth will also result in anesthesia of the mental nerve supplying the chin and lower lip. Anesthesia of the maxillary anterior teeth will also block sensation from the lower eyelid, lateral nose, and the upper lip. Numbness in these areas indicates successful local anesthesia.
Disorders of the trigeminal ganglion, within the skull, can give rise to paroxysms (sudden, severe bouts of pain) along the pathways of the sensory facial branches of the trigeminal nerve. Trigeminal neuralgia occurs more often in territories supplied by the maxillary (cranial nerve V-2) or mandibular (cranial nerve V-3) nerves. These episodes of pain can be triggered by just a light touch to the face or hot or cold foods in the mouth. Treatment sometimes consists of resection of the maxillary or mandibular division. Following resection, patients must chew very carefully to prevent biting the cheek. Patients who have undergone such a resection should visit their dentists frequently to monitor possible intraoral problems that the patient can no longer detect because intraoral pain is no longer a warning that something is wrong.
The mental nerve is a cutaneous branch of the inferior alveolar nerve. The mental nerve leaves the mandibular canal through the mental foramen and exits onto the face lateral to the chin. It immediately breaks up into three sets of branches.
The face is richly supplied with blood from various arteries, and the terminal branches of these various arteries anastomose freely (Figure 7-3). The entire blood supply is derived from either the internal or the external carotid arteries. Their facial branches travel as companion arteries to the sensory facial nerves described previously and, in general, carry the same names as the facial sensory nerves.
Figure 7-3 A, Superficial arteries of face. SO, Supraorbital artery; ST, supratrochlear artery; L, lacrimal artery; EN, external nasal artery; ZF, zygomaticofacial artery; ZT, zygomaticotemporal artery; IO, infraorbital artery; S, superficial temporal artery; M, mental artery; F, facial artery. B, Superficial veins of face. SO, Supraorbital vein; ST, supratrochlear vein; L, lacrimal vein; EN, external nasal vein; ZF, zygomaticofacial vein; IO, infraorbital vein; S, superficial temporal vein; M, mental vein; F, facial vein; DF, deep facial vein.
The dorsal nasal artery is the companion artery to the infratrochlear nerve. It emerges from the medial-superior angle of the orbit to supply the medial upper lid, the lacrimal sac, and the bridge of the nose.
The zygomatic artery passes through the zygomatic canal in the lateral wall of the orbit and divides into two terminal branches that emerge on the face. The zygomaticofacial artery emerges through the zygomaticofacial foramen to supply the skin of the prominence of the cheek. The zygomaticotemporal artery emerges through the zygomaticotemporal foramen to supply the skin of the anterior temporal region.
The infraorbital artery issues from the infraorbital foramen below the orbit and immediately breaks up into (1) inferior palpebral branches to the lower eyelid, (2) nasal branches to the lateral aspect of the nose, and (3) superior labial branches to the upper lip.
The buccal artery appears from under the cover of the ramus and masseter muscle. It spills onto the cheek, supplying the skin and mucous membrane of the cheek and vestibular gingiva of the mandibular molar area.
The facial artery, a collateral branch of the external carotid artery, leaves the submandibular region of the neck and ascends over the inferior border of the mandible through the antegonial notch. As the facial artery ascends obliquely on the face, it follows a somewhat tortuous route toward the medial angle of the eye. It passes between the more superficial and the deeper muscles of facial expression and supplies several branches to the face that anastomose freely with terminal branches of the maxillary and ophthalmic arteries.
As the facial artery travels diagonally toward the medial angle of the mouth, it gives off the inferior labial artery to the lower lip and the superior labial artery to the upper lip. The pulsations of the labial arteries may be felt in your own lip by grasping the lip between the thumb and forefinger.
The superficial temporal artery is a terminal branch of the external carotid artery that emerges onto the face between the jaw joint and the ear to ascend on the scalp. Just below the ear, it sends a branch forward as the transverse facial artery immediately below the zygomatic arch. It accompanies the auriculotemporal nerve on the side of the head.
It is occasionally convenient for the dentist to take a patient’s pulse in the head region. Two areas in the face where the pulse may be taken are (1) the facial artery as it passes through the antegonial notch and (2) the superficial temporal artery as it passes immediately anterior to the ear, above the tragus.
The face is profusely supplied by blood vessels. The areas of the external nose and lips receive a dual arterial supply from branches of both the facial and maxillary arteries. Facial lacerations bleed profusely, and occasionally branches of the external carotid artery or the external carotid itself must be ligated (tied off) to control hemorrhage.
The facial artery is vulnerable in oral surgery procedures on the buccal aspect of the mandibular molar region. Excessive force and improper techniques can sever the facial artery as it ascends onto the mandible in the antegonial notch.
The veins of the face follow somewhat the same pattern of distribution as the arterial supply, except for a few small but important differences (see Figures 7-3 and 7-4). Veins generally show more variability in their distribution than do arteries.
For each of the named arteries described previously as facial branches of the ophthalmic artery or maxillary artery, there are corresponding veins of the same name that flow in the opposite direction. The veins of the forehead, scalp, and upper lid flow to the superior ophthalmic vein in the orbit; the veins of the upper lip, lateral nose, and lower lid flow via the infraorbital vein to the pterygoid plexus of veins in the infratemporal region.
The facial vein roughly parallels the route of the facial artery. However, it is more posterior, takes a straighter and less tortuous course, and travels in the opposite direction. The facial vein originates and gathers tributaries in the following manner:
The facial vein then descends over the inferior border near the antegonial notch to enter the submandibular region of the neck. Unlike the facial artery, the vein takes a superficial course through the submandibular region.
The retromandibular vein is formed from two sources. The superficial temporal vein drains the scalp and side of the head. It descends anterior to the ear and plunges into the substance of the parotid gland. Here it unites with the maxillary vein from the infratemporal region.
The retromandibular vein continues inferiorly, picking up glandular tributaries, and leaves the gland at its inferior border. At the angle of the mandible, the retromandibular vein divides into an anterior and a posterior division in the neck. The posterior division of the retromandibular vein unites with the posterior auricular vein from behind the ear to form the external jugular vein.
The anterior division of the retromandibular vein joins the facial vein in the neck to form the short common facial vein. The common facial vein drains deep to the internal jugular vein (see Chapter 5).
Infections arising from the face or the orbit can spread through these venous communications to the cavernous sinus and cause an infective intracranial thrombus (clot). The condition is termed cavernous sinus thrombosis, is difficult to eradicate even with extensive antibiotic therapy, and may be fatal. Organisms in the blood from infections on the face could, therefore, be swept through the orbit to the cavernous sinus, where a secondary, more dangerous site of infection could develop.
The muscles of the face, or muscles of facial expression, are derived from the second branchial arch and are supplied by the cranial nerve of the second arch, the facial nerve (cranial nerve VII) (Figure 7-5 and Table 7-1). The muscles of the scalp and the platysma muscle of the neck belong to the same muscle group.
In general, the muscles are found within the superficial fascia around the facial orifices. They perform two functions: (1) as dilators and sphincters they control the openings of the orifices, and (2) as movers of overlying skin they reflect the various facial expressions.
Most facial muscles originate from bone or from fascia, and all insert into the skin of the face. Upon contraction, therefore, they move the facial skin into various attitudes that reflect emotions, such as smiling, grinning, frowning, and forehead wrinkling of puzzlement. The muscles are grouped by regions.
The orbicularis oris muscle is the sphincter of the oral aperture and lies within the upper and lower lips, encircling the mouth. Its fibers originate mainly from contributions of other facial muscles that converge on the mouth. A few intrinsic fibers arise from labial alveolar bone overlying the upper and lower incisors.
The levator anguli oris muscle originates from the canine fossa of the maxilla immediately inferior to the infraorbital foramen. It inserts into the angle of the mouth, blending with fibers of the orbicularis oris muscle. The function is self-descriptive; the muscle lifts the angles of the mouth.
The depressor anguli oris is a triangular muscle, the base of which originates from the external oblique line of the mandible. The ascending fibers converge at the apex to insert into the angle of the mouth from below and blend with the fibers of the orbicularis oris muscle. The depressor anguli oris muscle pulls the angles of the mouth downward.
The zygomaticus major muscle arises from the facial aspect of the zygomatic bone. Its fibers angle downward and medially to insert into the angle of the mouth and blend with the orbicularis oris muscle. It is the “laughing” muscle of the face, drawing the angle of the mouth upward and backward.
The risorius muscle is a thin, wispy muscle that arises from parotid and masseteric fascia, plus a small contribution from upper fibers of platysma muscle sweeping up from the neck. Risorius muscle inserts transversely into the angle of the mouth and retracts the angle posteriorly, as in grinning.
The muscle fibers sweep anteriorly through the cheek as a flattened sheet. On approaching the angles of the mouth, the upper fibers sweep inferiorly and the lower fibers sweep superiorly to blend with the orbicularis oris muscle.
The buccinator muscle presses the cheek against the vestibular surfaces of the molar teeth. In doing so, it aids in mastication by pushing food onto the occlusal surfaces of the teeth in opposition to the tongue, which pushes the food in the opposite direction. The buccinator muscle also prevents the cheeks from expanding when forcefully expelling air from the oral cavity against resistance, as in playing wind or brass musical instruments.
The orbicularis oculi muscle is contained within the upper and lower eyelids (palpebrae). It is a sphincteric muscle and helps close the eyelids. The orbicularis oculi muscle originates as three components.
The orbital portion originates from bone of the upper medial orbital margin, encircles the orbital margin, and inserts from below into the prominent medial palpebral ligament. The ligament, in turn, is anchored to the anterior lacrimal crest of the maxilla.
The palpebral portion arises from the medial palpebral ligament and arches laterally within the upper and lower eyelids. The fibers of the upper and lower lids interdigitate laterally at the less prominent lateral palpebral ligament.
The palpebral portion lightly approximates the lids, as in light blinking or during sleep. The orbital portion, because of its attachment to bone of the orbital periphery, is in a good mechanical position to forcibly squeeze the lids tightly to block out foreign objects or intense light. The lacrimal portion holds the lids against the globe of the eyeball for more even distribution of moistening tears and guiding tears to the small openings, or puncta, of the nasolacrimal apparatus for tear removal to the nasal cavity.
The mentalis muscle is a conical muscle, the apex of which arises from the mandibular incisive fossa. The fibers converge as the base to insert into the skin of the chin superficially. Contraction of the fibers puckers the skin overlying the chin and helps the orbicularis oris muscle in clearing food from the mandibular labial vestibule.
The transverse portion (compressor nares) arises from the upper portion of the canine ridge of the maxilla. It arches upward and medially to insert along with its counterpart in a midline aponeurosis overlying the nasal cartilages.
The actions of the nasalis muscle are insignificant, yet to the observant clinician, they are of diagnostic value. A true nasal breather can quite visibly flare the nostrils. Habitual mouth breathing caused by nasal obstruction decreases, if not eliminates, the ability to flare the nostrils. Mouth breathing is a cause of some dental malocclusions in children.
In children with class II malocclusions (small mandible in relation to the maxilla), the mentalis muscles are hyperactive when the lips are closed. The dimpling of the chin indicates hyperactive mentalis muscles.
The alar portion (dilator nares) arises from the nasal margin of the maxilla and inserts into the skin of the nostril. It acts to “flare” the nostrils. Some alar fibers sweep up to the ala and septum as the depressor septi muscle. These fibers tend to pull down on the septum and ala during nostril dilation.
The procerus muscle arises as small slips from fascia overlying the dorsum of the nose. The fibers sweep upward to insert into the skin overlying the glabella. Contraction produces transverse wrinkles over the bridge of the nose.
The corrugator is a small muscle slip that originates from the medial supraorbital margin. The fibers travel laterally to insert into the skin underlying the eyebrow. It produces vertical wrinkles over the glabella in certain individuals.
The frontalis muscle is the anterior component of the occipitofrontalis muscle of the scalp. It originates from a membranous sheet, or aponeurosis, on the scalp and inserts into the skin of the frontal region above the eyebrows. Contraction produces transverse wrinkling of the brow, as in worrying, or raising of the eyebrows, as in surprise.
The facial nerve exits from the skull through the stylomastoid foramen at the base of the skull (see Figure 7-2). It passes inferiorly and anteriorly for several millimeters, enters the substance of the parotid gland, and here breaks up into five main groups of branches that radiate from the anterior margin of the gland and travel to various areas of the face.
The temporal branches travel superiorly and anteriorly to supply facial muscles situated above the zygomatic arch, including the orbit and forehead. They innervate the anterior and superior auricular muscles, the frontalis muscle, and the superior portion of the orbicularis oculis muscle.
The zygomatic branches travel transversely across the face to supply facial muscles in the zygomatic, orbital, and infraorbital areas. They supply the inferior portion of the orbicularis oculis muscle, and the superior portions of the zygomaticus major, levator labii superioris, levator anguli oris, nasalis and orbicularis oris muscles.
Buccal branches supply muscles of the cheek and circumoral muscles. They innervate the buccinator and orbicularis oris muscles, and the inferior portions of the zygomaticus major, levator labii superioris, levator anguli oris, nasalis, and orbicularis oris muscles.
The motor branches of the facial nerve communicate with cutaneous branches of the trigeminal nerve on the face and cutaneous branches of spinal nerves in the neck. It is likely that these communications represent sensory proprioceptive contributions, which distribute with the facial nerve branches to the various facial muscles.
Damage to the facial nerve results in some form of facial paralysis (Figure 7-7). The type of paralysis is dependent upon where the lesion (damage) occurs.
Axons of the upper motor neurons of the facial nerve cross the midline of the brainstem to supply facial muscles of the contralateral side. The upper facial muscles (frontalis and orbicularis oculi) also receive axons from the same or ipsilateral side. Damage to the upper motor neurons of the facial nerve results in paralysis of the lower facial muscles on the contralateral side. The upper facial muscles continue to receive an ipsilateral nerve supply. Strokes are the most common cause of this type of facial paralysis.
Viral infections can cause inflammation of the facial nerve as it passes through the facial canal. Swelling of the nerve in the enclosed bony canal causes pressure and a temporary facial paralysis or Bell’s palsy.
The eyelids cannot close to lubricate the eye because the orbicularis oculi muscle is inactive and the levator palpebrae muscle, the opener of the upper eyelid acts unopposed. Tears fall onto the face because the punctum of the lower eyelid (hole that drains tears) is no longer applied closely to the eye (paralysis of the lacrimal portion of the orbicularis oculi).
Saliva may dribble from the mouth, and food cannot be chewed properly on the affected side because of paralysis of the buccinator and orbicularis oris muscles. In addition, expressive lines produced by facial muscles are obliterated, and facial distortion may occur because of contractions of unopposed contralateral facial muscles.
The upper and lower lips surround the mouth, or entrance to the oral cavity (Figure 7-8). The upper lip lies between the nose above and the opening of the mouth below. Laterally, the lips are separated from the cheeks by the nasolabial groove, a furrow extending from the ala of the nose to approximately 1 cm lateral to the angle of the mouth. The philtrum is a wide (6 to 7 mm), shallow trough extending from the nose to the red (vermilion) border of the upper lip. Superiorly, the philtrum ends at the columella, the fleshy external partition between the nostrils.
The skin of the lip exhibits all the general features of thin skin, such as hair, sweat, and sebaceous glands. As the skin of the lip approaches the mouth, it changes color abruptly to red. The point at which this change occurs is the vermilion border and marks the beginning of the red transitional zone between the external skin and the internal mucous membrane. The skin of the transitional zone is extremely thin and hairless, allowing the redness of the underlying capillary bed to show through.
The muscle of the lip is the orbicularis oris muscle, the sphincter of the mouth. In addition, the circumoral muscles, which contribute to the orbicularis oris muscle, occupy this layer. The muscles lie within the superficial fascia.
Within the submucosa lie numerous labial mucous glands, or labial glands. These can be felt by running the tongue against the bumpy internal surface of your own lips. These glands open directly through tiny duct openings to the vestibule of the mouth.
The transitional zone sweeps into the mouth and is transformed into true, moist, nonkeratinizing mucous membrane. The mucous membrane coats the intraoral vestibular portion of the lip and then reflects down from the upper lip or up from the lower lip onto the alveolar process. The fold is the vestibular, or mucolabial, fold. The mucous membrane ascends on the alveolar process and turns abruptly to gingiva (gums). The demarcation is abrupt, with the gingiva assuming a lighter color and a stippled surface. The gingiva is firmly attached to the underlying alveolar bone. The gingiva is described in greater detail in section 8 of this chapter.
These are folds of mucous membrane that run in the midline of the upper lip and the lower lip from the mucosa to the labial gingiva. Secondary frenula are found in the molar and premolar areas as well.
Angular cheilosis is an inflammation and cracking of the skin and transition zone at the angles of the mouth. It is a condition that is usually associated with a B vitamin deficiency. It may also be infected with bacteria and/or fungi and is called perlèche. Treatment consists of a regimen of antibacterial and antifungal medication. This condition is common in older edentulous patients with angular wrinkling and leakage of saliva contributing to irritation and inflammation. Restoration of facial contours with dentures helps rectify this problem.
Herpes labialis, or cold sores, are painful vesicular lesions (watery blisters) at the vermilion border of the lip that are caused by the herpes simplex virus. The vesicles rupture and form yellow crusted lesions that last about 10 days. Primary infections occur in early childhood and, after remission, the virus remains dormant in the trigeminal ganglion. The virus is opportunistic and can recur with fever-producing diseases, onset of menstruation, anxiety, exposure to sun, and occasionally dental treatment.
A labial mucocele or mucous retention cyst is a labial mucous gland with a blocked secretory duct that causes the gland and the overlying epithelium to bulge and assume a bluish tinge. Mucoceles usually occur on the lower lip. Large or noticeable cysts can be surgically removed.
Squamous cell carcinoma is a type of cancer. An ulcerated (cratered) lesion on the vermilion border of usually the lower lip that does not appear to heal over a reasonable period of time should be under suspicion and investigated.
The cheeks form the lateral movable walls of the oral cavity (Figure 7-10). Externally, the cheek includes not only the movable portion but also the prominence of the cheek over the zygomatic arch. This terminology, however, is from common usage, and our definition of cheek is confined to the movable portion.
The mucosa of the cheek ends in a mucobuccal fold superiorly and inferiorly, that sweeps onto the alveolar process. As the mucosa ascends to the alveolar crest, it becomes firmly attached to the bone as the gingiva.
Occupying the space superficial to the buccinator muscle is a collection of fat, that is continuous with fat deposits deep to the ramus of the mandible and deep to the zygomatic arch lateral to the orbit. This fat depot is relatively larger in the infant, presumably to reinforce the cheeks and keep them from collapsing during sucking actions. Hence its name—the buccal sucking fat pad.
The skin of the nose continues beyond the opening of the external nares into the vestibule of the nose. Within the vestibule, the skin is less keratinized but contains hair follicles and sebaceous glands. Nasal hairs are long (more prominent in the adult male) and act to filter larger particles of dust from the inhaled air.
The muscle of the nose is the nasalis muscle, consisting of two sets of fibers: (1) the dilator nares, which flare the nostrils, and (2) the compressor nares, which flatten the nostrils (see Figure 7-5).
The external nose is supplied by (1) the dorsal nasal branch of the ophthalmic artery, (2) the external nasal branch of the anterior ethmoidal artery, (3) the nasal branch of the infraorbital artery, and (4) the nasal branch of the facial artery.
A single elastic cartilage provides support for the external ear (Figure 7-12). The pendulous lower portion, or earlobe, contains no cartilage but does contain fibroareolar tissue. The cartilage of the ear is continuous with the cartilage of the external auditory meatus (canal), leading within the petrous temporal bone to the middle ear.
The skin of the auricle is tightly bound to the cartilage, with no intervening subcutaneous layer. The skin funnels into the opening of the external auditory meatus and lines the canal and the lateral aspect of the tympanic membrane (eardrum).
The sensory innervation of the ear is from (1) the auriculotemporal nerve (from cranial nerve V-3), (2) the great auricular nerve (from anterior primary rami [APR] of C2 and C3), and (3) the lesser occipital nerve (from APR of C2 and C3).
Extremely thin skin covers the lids of the eye (Figure 7-14). At the margins of the eye, prominent hairs, or cilia, form two or three irregular rows along the lateral five sixths of the margin. Associated with the cilia are large sebaceous glands, or ciliary glands (glands of Zeis). Infected ciliary glands result in the common stye.
The orbital septum and tarsi form the “skeleton” of the eyelid (see Figure 7-14 and also Figure 7-34 later in this chapter). The orbital septum is a membranous connective tissue sheet that attaches to the periphery of the orbital margin. Medially, it attaches to the posterior lacrimal crest. The septum forms a curtain with an elliptical transverse opening, the palpebral fissure.
The margins of the septum around the palpebral fissure are thickened as tarsal plates, or tarsi. The tarsi are half-moon in outline, and the lower tarsus is not as large as the upper one. Medially, the tarsi attach to the anterior lacrimal crest via the stout medial palpebral ligament. The lateral anchorage is weaker via the less prominent lateral palpebral ligament to the lateral margin of the orbit.
The blood supply to the scalp arises from various sources but basically arises from branches of the ophthalmic and external carotid arteries (Figure 7-15). The arteries ascend to the scalp from the face below in a semicircle.
Figure 7-15 Superior view of the scalp to show the nerves and arteries. Left: ST, Supratrochlear nerve; SO, supraorbital nerve; ZT, zygomaticotemporal nerve; AT, auriculotemporal nerve; LO, lesser occipital nerve; GO, greater occipital nerve; 3rd O, third occipital nerve. Right: ST, Supratrochlear artery; SO, supraorbital artery; STemp, superficial temporal artery; PA, posterior auricular artery; O, occipital artery.
The cutaneous nerve supply to the scalp arises from the three divisions of the trigeminal nerve anterior to the ear. Posterior to the ear, the nerve supply consists of spinal cutaneous nerves from the neck.