S6 Face - LabLink
Click here for a condensed, step-by-step dissection summary.
Locate and identify the relevant osteological features
Find these structures:
- Frontal bone
- Supra-orbital foramen or notch
- Alveolar processes of maxilla
- Infra-orbital foramen
- Zygomatic bone
- Zygomaticofacial foramen
- Zygomaticotemporal foramen
- Nasal bone
- Sphenoid bone
- Hamulus (of medial pterygoid plate)
- Ethmoid bone
- Groove for external nasal nerve
- Mental foramen
- Mental protuberance
- Oblique line
- Apex of retromolar trigone
Locate features of the nose and mouth
Find these structures:
- Ala of the nose
- Nasal columella
- Nasolabial fold
- Mentolabial fold
1.) Examine the external features of the nose, and appreciate the relationship between the nose and the upper lip.
Note: The nostrils are surrounded by cartilage-supported lateral arches called the ala of nose. ‘Ala’ (L) is a wing or wing-like structure.
Note: The nasal columella is the skin-covered external portion of the nasal septum.
Note: The philtrum is the region of the upper lip between the nasal columella and the vermilion border. The philtrum is bounded laterally by philtral ridges.
Photo 1. Nose
Note: When present, nasolabial folds extend from lateral to the nose and curve toward the angles of the mouth. They are often referred to as ‘smile lines,’ and often deepen with age.
Note: When present, the mentolabial fold is a horizontal cleft between the lower lip and the chin.
Photo 2. Nose and mouth
Skin the face
2.) Remove the remainder of the skin from the face. Do not skin the nose or ears. Skin near the eyes, but do not skin the (palpebral parts of the orbicularis oculi m.) eyelids.
Note: The skin of the face rests upon a layer of fibro-adipose tissue of various depths, which is superficial to the superficial musculo-aponeurotic system (SMAS), a fascial layer that invests the muscles of facial expression to a variable extent. The SMAS extends from the platysma mm. of the cervical region to the epicranial aponeurosis of the cranium. Branches of the facial n. (CN VII) are found deep to the SMAS. The fibro-adipose tissue is rich with dense connective tissues, thus allowing the facial muscles to move and shape the skin of the face.
Photo 3. Procedural: skinned face
3.) Review the location of the parotid gland from the previous session. Locate facial n. brs. and the parotid duct emerging from the anterior margin of the parotid.
Photo 4. Parotid gland, with proximal portions of facial n. brs.
4.) Determine a dissection plan for each side of the face: a superficial dissection (which will retain the facial n. branches, and include facial mm.) and a deep dissection (which will include facial mm. and cutaneous nn.).
Clean the fascia of the superficial face, and locate branches of the facial (CN VII) n., superficial side
Find these structures:
- Facial n. (CN VII) brs.
- Temporal brs.
- Zygomatic brs.
- Buccal brs.
- Marginal mandibular br.
- Cervical br. (seen previously)
- Parotid duct
5.) Trace and clean the facial n. branches to their distal connections and reaches. Often it is difficult to distinguish facial n. brs. and the tough, fibro-adipose tissue in this area. Superficial, medial portions of the parotid gland may be removed to find larger trunks of the facial n., in order to better trace the smaller, distal connections. Make sure to retain the bulk of the parotid gland on this section of the head. Try to preserve any connections among these branches, especially in the vicinity of the buccal brs. As you work medially from the parotid, locate the parotid (Stensen’s) duct, and clean the duct to its course through the buccinator m.
Photo 5. Parotid gland, duct, and facial n. brs.
Note: The facial n. exits the stylomastoid foramen, then divides into two divisions: the temporofacial division (superiorly) and the cervicofacial division (inferiorly). These divisions and their branches course through the parotid gland. The temporofacial division typically gives rise to the temporal brs., zygomatic brs., and a portion of the buccal brs. The cervicofacial division typically gives rise to a portion of the buccal brs., marginal mandibular br., and the cervical br.
Note: The stylomastoid foramen sits between the mastoid and styloid processes of the temporal bone, and transmits the facial n.
Note: The parotid duct typically arises at the anterior border of the parotid gland, travels superficial to the masseter m., dives into the buccal fascial space, and then pierces the buccinator m. The parotid duct is variable in path and size, but is typically 1-3 mm in diameter. The parotid duct conducts saliva from the parotid gland, through the buccinator m., opening through a papilla of mucosa opposite the maxillary second molars.
Photo 6. Facial n. brs. and divisions
Locate and remove fascia from the facial muscles
6.) While mindful of the facial n. brs. and parotid duct, clean any remaining subcutaneous fibro-adipose tissue from the SMAS to reveal the craniofacial and epicranial muscles.
Note: Muscles of the superficial head fall into two major groups: epicranial and craniofacial. Epicranial muscles are few, primarily act upon the scalp, and are best represented by the occipitofrontalis m.: a muscle with two bellies (frontal and occipital) connected by an intermediate epicranial aponeurosis. Craniofacial muscles are located in the facial region and are often referred to as muscles of facial expression, as they move the skin of the face.
Find these structures:
- Epicranial muscles
- Occipitofrontalis m.
- Frontal belly
- Epicranial aponeurosis
- Occipital belly
- Occipitofrontalis m.
- Craniofacial muscles (of facial expression)
- Orbicularis oculi m.
- Orbital part
- Corrugator supercilii m.
- Buccinator m.
- Orbicularis oris m.
- Levator labii superioris m.
- Levator anguli oris m.
- Zygomaticus major m.
- Zygomaticus minor m.
- Risorius m.
- Depressor anguli oris m.
- Depressor labii inferioris m.
- Mentalis m.
- Nasalis m.
- Transverse part (compressor naris m.)
- Alar part (dilator naris m.)
- Levator labii superioris alaeque nasi m.
- Orbicularis oculi m.
Note: The frontal belly of the occipitofrontalis m. is sometimes referred to as the frontalis m. It connects the skin of the brow with the epicranial aponeurosis. When active, the frontal belly moves the brow superiorly and creases the forehead. The frontal belly is innervated by temporal brs. of the facial n. The occipital belly is sometime referred to as the occipitalis m., and connects the epicranial aponeurosis to the superior nuchal line of the occipital bone. The occipital belly is innervated by the posterior auricular br. of the facial n.
Note: Many of the upper motor neurons of the temporofacial division originate bilaterally in the cerebral cortex, whereas the upper motor neurons for the cervicofacial division are sourced in the contralateral cerebral cortex. A cerebrovascular accident (CVA, or a stroke) may typically present with contralateral facial muscle paralysis of the lower face, whereas facial n. (Bell’s) palsy typically presents with total ipsilateral facial muscle paralysis. Thus, an individual suffering a CVA may be able to elevate the skin of their brow (wrinkle the forehead), whereas an individual with a facial n. palsy cannot elevate the skin of their brow.
Photo 7. Frontal belly & epicranial aponeurosis of occipitofrontalis m.
Photo 8. Frontal belly, epicranial aponeurosis, and occipital belly of occipitofrontalis m.
Note: A series of three muscles, auricularis anterior, superior, & posterior, attach the auricle of the ear to either the epicranial aponeurosis (anterior & superior mm.), or the mastoid process (posterior m.). The auricularis muscles are typically quite gracile, and often greatly atrophy with age. When activated, the auricularis mm. pull on the auricle of the ear (wiggle the ear).
Photo 9. Auricularis mm.
Note: The orbicularis oculi m. is a sphincteric, circumferential muscle of three parts (orbital, palpebral, and lacrimal), surrounding the orbit. The orbital part encircles the palpebral part. The palpebral part is typically involuntarily controlled (blinking), whereas the orbital part is typically voluntarily controlled (shutting the eyes tightly). The orbicularis oculi is innervated by temporal and zygomatic brs. of the facial n.
Photo 10. Orbicularis oculi m.
Note: The corrugator supercilii mm. connect the medial aspects of the superciliary arches of the frontal bone (deep to the orbicularis oculi mm.) with the skin of the medial brow. When activated, these muscles pull down on the skin of (furrow) the brow. The corrugator supercilii mm. are innervated by the temporal brs. of the facial n.
Photo 11. Corrugator supercilii mm.
Note: The craniofacial muscles controlling the shape and positioning of the lips (and thus the mouth) converge into dense fibromuscular ‘wheels’ at each angle of the mouth. This structure is called the modiolus, and can be palpated between the skin and oral mucosa.
Note: The shape and positioning of the lips is controlled by several buccolabial muscles controlling the upper lip (e.g. levator labii superioris m.,), lower lip, oral opening (e.g. zygomaticus major & minor mm., levator anguli oris m., risorius m., depressor anguli oris m., and orbicularis oris m.), and cheeks (e.g. buccinator m.).
Note: The levator labii superioris m., zygomaticus minor m., & zygomaticus major m. form a series of medial-to-lateral connections between the modiolus and the lower margin of the orbit/zygomatic bone. These three muscles are innervated by zygomatic and buccal brs. of the facial n. (CN VII). The levator labii superioris m. elevates and weakly everts the upper lip. The zygomaticus minor m. elevates the upper lip to expose the maxillary incisors and canines. The zygomaticus major m. elevates and draws the angle of the mouth laterally. These three muscles activated sequentially contribute to an increasingly wide smile.
Note: The infra-orbital (= canine) fascial space is deep to the “quadratus labii superioris m.” group, which consists of the levator labii superioris alaeque nasi m., levator labii superioris m., and the zygomaticus minor m. The buccal fascial space is continuous posteriorly with the infra-orbital space. Odontogenic infections of the ipsilateral canine or first premolar may spread to this space, causing infra-orbital edema. Left untreated, infection may spread to either the buccal space, and/or to the orbital vasculature, and the cavernous sinuses beyond. The angular a. & v. and the infra-orbital n. (of V2) are found in this space.
Note: With the advanced ages of many anatomical donors, it is not uncommon for some of the buccolabial mm. to have significantly atrophied. If you cannot find particular muscles on your donor, look at other donors or plastinated specimens.
Photo 12. Buccolabial muscles
Note: The levator anguli oris m. attaches the modiolus of the mouth to the canine fossa of the maxilla. Innervated by buccal brs. of the facial n., when activated, the levator anguli oris m. pulls the angle of the mouth laterally and superiorly.
Note: The risorius m., a highly variable muscle, attaches the modiolus of the mouth to the parotid fascia, and surrounding structures. The risorius m. is innervated by buccal brs. of the facial n. When activated, the risorius pulls the corners of the mouth laterally, as in a smirk.
Note: The depressor anguli oris draws the modiolus inferiorly and laterally, towards the oblique line of the mandible. The depressor anguli oris m. is innervated by buccal and marginal mandibular brs. of the facial n.
Photo 13. Buccolabial muscles: depressor anguli oris, risorius mm.
Note: The depressor labii inferioris m. attaches the skin of the lower lip to the oblique line of the mandible. Innervated by the marginal mandibular br. of the facial n., when activated the depressor labii inferioris m. draws the lower lip inferiorly.
Note: The mentalis m. attaches the skin of the chin to the incisive fossa of the mandible. The mentalis m. is innervated by the marginal mandibular br. of the facial n., when activated the mentalis m. elevates the skin of the chin and lower lip (to form a pout).
Photo 14. Buccolabial muscles: depressor labii inferioris m. & mentalis m.)
Note: The orbicularis oris m. is a complex association of quadrants (upper, lower, right, & left) of muscle that encircle the oral opening. When activated in total, these quadrants purse (pucker) the lips, such as to enable the gesture of a kiss. The orbicularis oris m. is innervated by buccal and marginal mandibular brs. of the facial n.
Note: The buccinator m. covers the area superficial to the lateral teeth-bearing regions of the maxilla and mandible. The buccinator m. is innervated by buccal brs. of the facial n. When activated, the buccinator m. draws the cheeks toward the teeth (to bring food into the occlusal plane) while tightening the buccal mucosa (to withdraw the mucosa from the occlusal plane). The buccinator m. also forcefully directs and/or expels air from the cheeks, such as when playing a wind instrument, or when whistling.
Photo 15. Buccolabial muscles: orbicularis oris m. & buccinator m.
7.) Skin the entirety of the nose, and locate the nasal muscles.
Note: The external structure of the nose is covered by two muscles: medially, the nasalis m., and laterally, the levator labii superioris alaeque nasi m.
Note: The nasalis m. consists of two distinct parts: the transverse part (compressor naris m.) and the alar part (dilator naris m.). The nasalis m. is innervated by both zygomatic and buccal brs. of the facial n. The transverse part attaches the portion of the maxilla superolateral to the incisive fossa to the midline of the bridge of the nose. When activated, the transverse part compresses the naris. The alar part attaches the alar cartilage to the portion of the maxilla superolateral to the incisive fossa (medial to the attachment of the transverse part). When activated, the alar part dilates the naris.
Note: The levator labii superioris alaeque nasi m. attaches the frontal process of the maxilla to both: fascia superficial to the alar part of the nasalis m. and the skin superficial to the levator labii superioris m. The levator labii superioris alaeque nasi m. is innervated by both zygomatic and buccal brs. of the facial n. When activated, this muscle dilates the naris and elevates the upper lip.
Photo 16. Nasal muscles
Locate cutaneous branches of the trigeminal n. (CN V), deep side
Find these structures:
- Cutaneous branches of trigeminal n. (CN V)
- Supra-orbital n. (of V1)
- Infra-orbital n. (of V2)
- Mental n. (of V3)
- Auriculotemporal n. (of V3)
Note: The trigeminal n. (CN V) is responsible for innervating muscles of mastication (efferent) and sensation of the skin of the face (afferent). The trigeminal n. has three divisions: ophthalmic n. (V1), maxillary n. (V2), and mandibular n. (V3). The complete courses and functions of these divisions will be seen and discussed in subsequent sessions. A focus of this session are the nerves (and their branches) of these divisions afferently serving the skin of the face.
Photo 17. Lateral view of face showing regions afferently served by V1, V2, & V3
8.) Using blunt dissection with minimal disruption of the surrounding tissue, locate the: supra-orbital foramen (or notch), infra-orbital foramen, and the mental foramen. Find and identify the nerves they transmit.
Note: The supra-orbital n. is the terminal continuation of the frontal n. through the supra-orbital notch or foramen to afferently serve the conjunctiva, mucosa of the frontal sinus, and skin of the superior palpebra, forehead, and epicranial scalp. The supra-orbital n. is a branch of the ophthalmic n. (V1). Variations of crania include those with supra-orbital notches and those with supra-orbital foramen. Either of these structures, when present, are found along the superior rim of the orbit, nearly halfway between the midpoint of the superior rim and the medial rim of the orbit.
Note: The supratrochlear n. is also a continuation of the frontal n. (the supra-orbital n. and supratrochlear n. arise from the bifurcation of the frontal n. in the superior orbit). The supratrochlear n. gets its name from passing superiorly to the trochlea of the superior oblique m. in the orbit. It innervates the skin of the: medial forehead and eyelid, and the medial sclera of the eye.
Note: The infra-orbital n. is the branch of the maxillary n. (V2) which exits the infra-orbital foramen of the maxilla. The infra-orbital foramen is below the orbit, approximately in-line with (or just lateral to) the supra-orbital foramen (or notch) above. The infra-orbital n. afferently supplies the mucosa of the maxillary sinus and gingiva, and skin of the: inferior palpebra, the lateral nose, upper lip, and cheek.
Note: Before arising through the infra-orbital foramen as the infra-orbital n., the maxillary n. (V2) gives off the zygomatic n., which bifurcates into the zygomaticotemporal n. and the zygomaticofacial n., each named for the foramen through which they exit the skull. The zygomaticotemporal n. innervates the skin superolateral to the orbit, and may also carry postganglionic parasympathetic fibers (secretomotor) to the lacrimal gland (a pathway to be discussed in a later session). The zygomaticofacial n. innervates skin lateral to the orbit.
Note: The mental n. is the terminal continuation of the inferior alveolar n., a branch of the mandibular n. (V3), which passes through the mental foramen of the mandible to afferently serve the mandibular gingiva, and skin of the: lower lip and chin.
Photo 18. Supra-orbital n., supratrochlear n., infra-orbital n., and mental n.
Photo 19. Supra-orbital, infra-orbital, and mental foramina
9.) Using blunt dissection, locate the cutaneous portion of the auriculotemporal n.
Note: As previously discussed, the auriculotemporal n. is a branch of the mandibular n. (V3). The auriculotemporal n. serves several functions:
- transmitting secretomotor postganglionic parasympathetic fibers to the parotid gland (from the otic ganglion; preganglionic fibers from glossopharyngeal n.),
- afferently serving the termporomandibular joint, and
- afferently serving the skin of the: tragus of the ear, the external auditory meatus, and the area anterosuperior to the ear.
Note: The cutaneous portion of the auriculotemporal n. may be found accompanying the superficial temporal a. & v. superiorly from the parotid gland.
Photo 20. Auriculotemporal n., cutaneous portion
Locate vasculature of the face
Find these structures:
- Superficial temporal v.
- Facial v.
- Deep facial v.
- Angular v.
- External carotid a.
- Facial a.
- Superior labial br.
- Inferior labial br.
- Lateral nasal br.
- Angular a.
- Superficial temporal a.
- Facial a.
10.) On the side of face with the parotid gland removed, locate the retromandibular v. and its superior tributary, the superficial temporal v. Follow the retromandibular v. to its potential junctions with the facial v. (into the internal jugular v.) and the posterior auricular v. (to form the external jugular v.).
Note: The superficial temporal v. typically accompanies the superficial temporal a. and the auriculotemporal n. superior to the parotid gland.
Note: The superficial temporal v. typically unites with the maxillary v. to form the retromandibular v. The retromandibular v. may divide into anterior and posterior divisions. The anterior division of the retromandibular v. typically unites with the facial v. before joining the internal jugular v. The posterior division of the retromandibular v. typically unites with the posterior auricular v. to form the external jugular v.
Photo 21. Facial veins
11.) Locate the facial a. and v. Trace the course of the facial a. from the external carotid a. to the medial aspect of the eye. Locate the major branches of the facial a. Locate major branches of the facial v.
Note: The superior thyroid a., the lingual a., and the facial a. are typically the first three anteriorly oriented branches of the external carotid a.
Note: The facial a. traverses the submandibular triangle before emerging over the body of the mandible (anterior to the masseter m.), accompanied by the facial v., deep to the branches of the facial n. The artery ascends and supplies structures of the face.
Photo 22. Lateral view of the facial a.
Note: The facial a. has several branches, major branches include the: inferior labial br., superior labial br., and the nasal br. The labial branches adjacent to the modiolus of the mouth and run courses between the orbicularis oris m. and the mucous membrane. The labial branches often anastomose with their contralateral counterparts. The lateral nasal br. often arises lateral to the nose, and anastomoses with its contralateral counterpart. In some cases, the lateral nasal br. may arise from the superior labial br. The angular a. is the terminal branch of the facial a. that courses toward the medial canthus of the eye.
Photo 23. Facial a. brs.
Note: The facial v. and its branches mirror the distribution of the facial a. and its branches. The angular v. is valveless and receives the supra-orbital v. and supratrochlear v. to drain the forehead and regions medial to the eye. The deep facial v. drains the pterygoid plexus of veins and deep face, is valveless, and joins the facial v. anterior to the masseter m.
Note: Anastomoses between facial v. branches may allow infections a direct route into the cavernous sinus. For example, anastomoses between the angular v. and the superior and inferior ophthalmic vv. may allow infections from the ‘danger area of the face’ a direct route into the cavernous sinus. Likewise, infections may move through the deep facial v. through the pterygoid plexus of veins into the cavernous sinus.