1. FACE, EYELIDS,
LACRIMAL APPARATUS
& SCALP
Steven J. Zehren, Ph.D.

2. BONES OF THE FACE

3. SKULL (ANTERIOR VIEW) Supraorbital f. NASAL LACRIMAL ZYGOMATIC
INF. NASAL CONCHA
The FACIAL BONES are the nasal, lacrimal, zygomatic, maxilla, mandible, vomer, inf. nasal concha and palatine (not shown). All of these bones (except the inf. concha) are dermal in origin (ie, they ossify directly from mesenchyme). The piriform (pear-shaped) aperture (not labelled) leads into the nasal cavity. Three foramina lie in a vertical line --- the supraorbital, infraorbital and mental. These foramina transmit cutaneous brs. of V1, V2 and V3 (resp.). (X Note also the tiny zygomaticofacial f. for a cutaneous nerve of the same name (br. of V2)).
The MAXILLA is described as a hollow, four-sided pyramid lying on its side. The base of the pyramid (nasal surface) contributes to the lateral wall of the nasal cavity; the apex projects into its zygomatic pr. The other three sides (in addition to the base) are the orbital surface, facial surface and infratemporal surface (not shown). The maxilla also has four processes --- frontal, zygomatic, alveolar and palatine (not shown). The "hollow" of the pyramid is the maxillary (air) sinus --- the largest of the paranasal sinuses. (The bony elevation over the root of the canine tooth is the canine eminence. Anterior to this eminence is a depression over the root of the lateral incisor (incisive fossa). Posterior to the eminence is a depression over the roots of the premolars (canine fossa)).
The MANDIBLE is a U-shaped bone with a horizontal body and two vertical rami (the body and ramus meet at the angle of the mandible (not labelled)). The alveolar pr. (not labelled) has sockets for the teeth. In the midline the body shows a mental protuberance and on either side is a mental tubercle. The mental protuberance and tubercles constitute the CHIN WHICH IS A FEATURE UNIQUE TO MAN!
VOMER
MAXILLA
MANDIBLE
Zygomatic pr.
Ramus
Orbital surface
Body
Infraorbital f.
Mental f.
Frontal pr.
Mental tubercle
Alveolar pr.
Mental protuberance

4. SKULL (LATERAL VIEW) Temporomandibular Joint (TMJ) LACRIMAL NASAL
MAXILLA
Frontal pr.
Infraorbital f.
MANDIBLE
In this LATERAL VIEW OF THE MANDIBLE note the following features. The EXT. OBLIQUE LINE (not labelled) runs from the mental tubercle to the ant. border of the ramus. The nearly horizontal ledge in the molar region between the ext. oblique line and alveolar pr. is the BUCCAL SHELF (not labelled). This marks the location of the buccal n.
The MENTAL F. lies near the apex (root end) of the second premolar. On dental radiographs it looks dark, similar to a lesion formed by a periapical abscess, esp. when it is superimposed over the premolar root apex. The mental f. is directed laterally, superiorly and posteriorly.
The head of the mandible articulates with the temporal bone at the TEMPOROMANDIBULAR JOINT (TMJ). This is the only synovial joint in the skull (other than the joints between the ear ossicles). The mandible is the largest and strongest bone of the skull but is nevertheless subject to fractures. Usually when the mandible breaks there are two fractures and they often occur on opposite sides; thus if one fracture is observed a search should be made for another.
The ZYGOMATIC ARCH is a bar of bone formed by the zygomatic and temporal bones. It is the most frequently broken "bone" of the face. The zygomatic arch is for the origin of the masseter, a muscle of mastication .
Alveolar pr.
Head
Mandibular notch
Coronoid pr.
ZYGOMATIC
Ramus
Body
Zygomatic arch
Mental f.

5. MANDIBLE (MEDIAL VIEW)
Mandibular
foramen
(inf. alveolar n.)
The medial surface of the ramus of the mandible has a foramen (mandibular f.) for the entrance of the inferior alveolar n. and vessels.

6. INFERIOR ALVEOLAR AND MENTAL NERVES
The inferior alveolar n. runs within the mandibular canal inside the mandible, giving off branches to the lower teeth. It also gives of the mental n. which emerges from the mental foramen and which is sensory to the lower lip and chin.
Inferior alveolar n.
(w/in mandibular canal)
Mental n.
(emerging from mental f.)

7. RESORPTION OF THE ALVEOLAR PROCESS OF THE MANDIBLE
WITH THE LOSS OF TEETH IN ELDERLY PEOPLE THE ALVEOLAR PR. OF THE MANDIBLE IS RESORBED. The mental f. (as well as the mandibular canal inside the mandible) may actually be exposed. Pressure on the mental and inf. alveolar nn. from dentures may cause the patient pain.
Mental foramen
Mandible of aged person

8. MAXILLARY SINUS (RELATIONSHIPS)
Opening of sinus into middle meatus
of nasal cavity
Maxillary sinus
Orbital surface
Infratemporal surface
Facial surface
Note large size of the maxillary sinus in the adult.
The four surfaces (sides) of the maxilla are also clearly shown (nasal surface not labelled).
Function of paranasal sinuses will be discussed in another lecture.
Roots of teeth

9. NEWBORN ADULT FACE FORMS 1/8 OF SKULL FACE FORMS 1/3 OF SKULL
In newborn, alveolar processes of maxilla and mandible poorly developed (no teeth). Paranasal sinuses (eg., maxillary sinus) are rudimentary. Hence, facial skeleton only 1/8th the size of the entire skull in the newborn.
In the newborn the two halves of the mandible are separated by fibrous tissue; fusion begins in the first year and is completed in the second.
FACE FORMS 1/8 OF SKULL
FACE FORMS 1/3 OF SKULL

10. SKULL OF NEWBORN (LATERAL VIEW)
1. Mastoid process absent at birth. Thus VII apt to be injured during delivery (at birth).
Mastoid process absent

11. MUSCLES OF FACE

12. MUSCLES OF FACIAL EXPRESSION
Unlike most skeletal muscles, the FACIAL MUSCLES INSERT INTO SKIN & ARE USED TO EXPRESS EMOTIONS.
Frontalis expresses surprise (I can’t believe he asked me this on a test!), corrugator supercilii used to frown (what does he want for an answer?), zygomaticus major used in smiling (this question is a “no brainer”), procerus produces transverse wrinkles across the skin of the nose (this question “stinks”), orbicularis oris protrudes the lips (this question “sucks”), & depressor anguli oris turns down the corner of the mouth (expression of grief after you get your anatomy exam back).

13. DERIVED FROM PHARYNGEAL ARCH 2
MUSCLES OF FACIAL EXPRESSION
DERIVED FROM PHARYNGEAL ARCH 2
The muscles of facial expression (salmon color) have a similar embryological origin; all are derived from the 2nd pharyngeal arch. As a result, they are all innervated by the nerve of that arch, namely the facial n. (VII).

14. MUSCLES OF FACIAL EXPRESSION
Epicranial aponeurosis
Orbicularis oculi
(palpebral part)
Orbicularis oculi
(orbital part)
Frontalis
Occipitalis
Levator labii superioris
Nasalis (transverse part)
Nasalis (alar part)
Orbicularis oris
Zygomaticus minor
Zygomaticus major
Several groups of facial muscles can be recognized. The MUSCLES OF THE SCALP & AURICLE include the FRONTALIS which originates from the galea aponeurotica (a broad aponeurosis on the top of the skull; hence the alternate name epicranial aponeurosis) and inserts into the skin of the eyebrow. It raises the eyebrow to express surprise. The OCCIPITALIS draws the scalp backward. Sustained contraction of the occipitalis and frontalis can cause a tension headache.
The MUSCLES AROUND THE OPENING OF THE ORBIT include the ORBICULARIS OCULI. This is a very imp. muscle which has three parts: 1) a palpebral part which closes the eye lightly (blinking and sleeping) 2) an orbital part which forcefully closes the eye (bright light, wind) and 3) a lacrimal part (not shown). The lacrimal part (difficult to find) may promote the flow of fluid through the lacrimal sac.
3. The MUSCLES OF THE NOSE include the NASALIS. This muscle dilates the nasal aperture.
The MUSCLES OF THE MOUTH are numerous. ORBICULARIS ORIS is a sphincter; it purses the lips as in whistling, kissing and sucking. LEVATOR LABII SUPERIORIS elevates the upper lip. MENTALIS protrudes the lower lip. BUCCINATOR compresses the cheek. (X It is therefore used in blowing and in keeping food between the occlusal surfaces of the teeth (ie, it keeps food out of the vestibule between the cheeks and teeth). Although the buccinator is imp. in eating it is NOT a true muscle of mastication. Rather, it is a muscle of facial expression (also used in smiling)).
One facial muscle extends into the SUPERFICIAL NECK REGION. It is the PLATYSMA ("platy" means flat). Platysma inserts into the corner of the mouth and draws it down to express fright. It also tenses the skin of the neck and makes it easier for me to shave !
Mentalis
Depressor labii inferioris
Depressor anguli oris
Buccinator
Risorius
Platysma

15. ORIGIN OF BUCCINATOR MUSCLE
Alveolar process
of maxilla
The ORIGIN OF THE BUCCINATOR is the pterygomandibular raphe and the alveolar prs. of the maxilla and mandible. A raphe is a fibrous line where two muscles meet edge to edge. In this case the buccinator intersects with the sup. pharyngeal constrictor (which also takes part of its origin from this raphe). The raphe is appropriately named because it stretches between the PTERYGOID hamulus of the sphenoid bone above (not shown) and the posterior end of the mylohoid line of the MANDIBLE below (not shown). Note that the buccinator is pierced by the parotid duct.
Parotid duct
Superior pharyngeal constrictor m.
Buccinator m.
Pterygomandibular raphe
Alveolar process of mandible

16. INSERTION OF BUCCINATOR MUSCLE
Parotid duct
Buccinator m.
The BUCCINATOR INSERTS into the lips where it intermingles with the orbicularis oris.
Orbicularis oris m.

17. FUNCTION OF THE BUCCINATOR MUSCLE
(coronal section through oral cavity)
Oral vestibule
Buccinator
BUCCINATOR compresses the cheek. It is therefore used in blowing and in keeping food between the occlusal surfaces of the teeth (ie, it keeps food out of the vestibule between the cheeks and teeth). Although the buccinator is imp. in eating it is NOT a true muscle of mastication. Rather, it is a muscle of facial expression (also used in smiling).

18. NERVES OF FACE

19. FACIAL N. (VII) EXITS CRANIAL CAVITY VIA INTERNAL AUDITORY MEATUS
The FACIAL N. (VII) leaves the cranial cavity via the int. acoustic meatus. It then enters the facial canal, a bony passage in the petrous part of the temporal bone.
INTERNAL AUDITORY MEATUS
(VII & VIII)

20. VII EMERGES FROM STYLOMASTOID FORAMEN
STYLOID PROCESS
The lower end of the facial canal is the stylomastoid f. where VII emerges from the skull.
MASTOID PROCESS
STYLOMASTOID F.

21. FACIAL NERVE BRANCHES IN PAROTID GLAND
Temporal branches
Zygomatic branches
THE FACIAL NERVE IS THE MOTOR NERVE OF THE FACE. VII emerges from the skull base at the stylomastoid f. After giving off a branch to the post. belly of the digastric and stylohyoid mm., VII enters the parotid gland. Within the gland it divides into FIVE TERMINAL BRANCHES: 1) Temporal br. 2) Zygomatic br. 3) Buccal br. 4) Marginal mandibular br. and 5) Cervical br. (Mnemonic: "To Zanzibar By Motor Car" or "Two Zebras Bit My Camel"). These brs. fan out onto the face much like the five digits of your hand placed on the side of the face. The temporal br. innervates the frontalis and part of orbicularis oculi, the zygomatic br. the remainder of orbicularis oculi, the buccal br. the nasalis, orbicularis oris, levator labii superioris and buccinator, the marginal mandibular br. the mentalis and the cervical br. the platysma.
(X) Why do all of the muscles of facial expression as well as the post. belly of the digastric and stylohyoid have the same innervation? They are all derived embryologically from pharyngeal arch 2 so they are all innervated by the nerve of that arch (VII). In all cases the functional component is SVE.
The BUCCAL BR(S). OF VII passes superficial to the masseter m. IT SHOULD NOT BE CONFUSED WITH THE BUCCAL N. (A BR. OF V3) which is purely sensory (GSA) and enters the cheek deep to the masseter.
The MARGINAL MANDIBULAR BR. OF VII frequently (~20%) dips below the inf. margin of the mandible as it passes forward. It is in surgical danger in this situation.
Main trunk of VII
TO ZANZIBAR BY MOTOR CAR
Buccal branches
Marginal mandibular branch
Cervical branch

22. BELL’S PALSY
BELL'S PALSY refers to the condition in which the facial muscles are paralyzed on one side (In this case, the muscles on the right side of the patient’s face are paralyzed ; notice the drooping corner of his mouth, & the patient cannot close his eye). The cause of this condition is not always known but in some cases it is due to inflammation of VII as it passes through the narrow confines of the facial canal. Inflammation of the nerve causes compression of its fibers against the walls of the bony canal. Another suggested cause of Bell's palsy is constriction (due to cold exposure) of the stylomastoid branch of the post. auricular a. which supplies VII.

23. COURSE OF VII IN FACIAL CANAL
Int. auditory meatus
Greater petrosal n.
VII in facial canal
of temporal bone
Nerve to stapedius
Stylomastoid for.
Chorda tympani n.
The SYMPTOMS OF BELL'S PALSY VARY ACCORDING TO THE EXACT SITE OF COMPRESSION. If VII is compressed just superior to the stylomastoid f. only ipsilateral facial paralysis results. On the other hand, compression of VII proximal to the geniculate ganglion (not labelled) results in loss of all functions of the nerve. Thus, in addition to facial paralysis the patient exhibits: 1) a "DRY EYE" (because the gr. petrosal n. carrying parasympathetic fibers to the lacrimal gl. is compromised) 2) HYPERACUSIS (=painful sensitivity to sounds) (because the n. to the stapedius m., which protects the inner ear from loud sounds, is paralyzed) 3) AGEUSIA (=loss of taste) on the anterior two-thirds of the tongue (because taste fibers in the chorda tympani n. are affected) and 4) IMPAIRED SECRETION OF THE SUBMANDIBULAR & SUBLINGUAL SALIVARY GLS. (because parasympathetic fibers in the chorda tympani n. are also affected).
Branches to muscles
of facial expression

24. TRIGEMINAL NERVE (V) Ophthalmic N. (V1) (GSA) Trigeminal ganglion
Maxillary N. (V2)
(GSA)
Sensory root of
V ganglion
1. V has three main branches or divisions: Ophthalmic (V1), maxillary (V2) and mandibular (V3).
2. V has two major functions:
a. Skeletal motor to the muscles of mastication, plus a few other muscles also derived from pharyngeal arch 1.
b. General sensory fibers from the skin of the face, mucosa of the nasal and oral cavities and paranasal sinuses, the
teeth, etc. (V is chief general sensory n. of head).
All of the skeletal motor fibers (SVE) in V travel in V3, but the general sensory fibers (GSA) travel in all three branches. The sensory fibers have their cell bodies in the V ganglion. The central processes of these sensory neurons constitute the sensory root of the V ganglion (the sensory root travels back to the brain).
Mandibular N. (V3)
(GSA, SVE)

25. VERTEX – EAR – CHIN LINE Dorsal rami of Ophthalmic N. (V1)
cervical nerves
Ophthalmic N. (V1)
Maxillary N. (V2)
This is a GREAT PLATE because it highlights the fact that the TRIGEMINAL N. IS THE CHIEF SENSORY NERVE OF THE FACE. Note the VERTEX - EAR - CHIN LINE (vertex is highest point on skull) --- the skin anterior to this imaginary line is supplied by V; the skin posterior to the line by cervical nerves (dorsal or ventral rami). The only area of facial skin not innervated by V is that over the angle of the mandible and parotid gland.
EACH DIVISION OF V SUPPLIES AN AREA OF FACIAL SKIN. V1 supplies the forehead, upper eyelid and dorsum of the nose. V2 supplies the lower eyelid, upper lip and side of the nose. V3 supplies an L-shaped strip of skin including the lower lip and chin, lower cheek, and part of the ext. ear and temple. Since all of these nerves are supplying skin the functional component is GSA.
Ventral rami of
cervical nerves
Mandibular N. (V3)

26. CUTANEOUS NERVES OF HEAD AND NECK
OPHTHALMIC N.
Supraorbital n.
Supratrochlear n.
DORSAL RAMI
Lacrimal n.
Infratrochlear n.
Gr. occipital n. (C2)
Ant. ethmoidal n.
(ext. nasal br.)
3rd occipital n. (C3)
MAXILLARY N.
Infraorbital n.
Zygomaticofacial n.
Zygomaticotemporal n.
Note the INDIVIDUAL BRS. OF V1, V2 & V3 WHICH SUPPLY FACIAL SKIN. Students need to know their names and their precise cutaneous distributions (Don’t name all of the branches. However, note the buccal n. (br. of V3) which is sensory to the cheek, emerging deep to masseter m. and not to be confused w/buccal br. of VII which is motor).
VENTRAL RAMI
Lsr. occipital n. (C2,3)
MANDIBULAR N.
Gr. auricular n. (C2,3)
Mental n.
Transverse cervical n. (C2,3)
Buccal n.
Auriculotemporal n.
Supraclavicular nn. (C3,4)

27. VESSELS OF FACE

28. FACIAL ARTERY
The FACIAL A. is the major arterial supply to the face. The arteries of the face anastomose with each other and with those on the opposite side; hence lacerations of the face bleed profusely. The facial a. arises from the ext. carotid a. and enters the face by crossing the inf. border of the mandible. Its pulse can be taken at this point (anesthesiologists take facial pulses when standing at the head end of the operating table). The facial a. pursues a very tortuous course on the face, giving off brs. to the chin, lips and nose. It ends near the angle of the eye as the angular a.

29. ARTERIAL SUPPLY TO FACE
Branches of the ophthalmic a. (from int. carotid a.) contribute to the blood supply of the face.
Black: from internal carotid a.
(via ophthalmic a.)
Red: from external carotid a.

30. FACIAL VEIN
The FACIAL V. begins near the medial angle of the eye as the angular v., formed by the union of the supraorbital and supratrochlear vv. The facial v. pursues a straighter course than its companion a., and remains posterior to it. In the neck the facial v. unites with the ant. division of the retromandibular v. to form the common facial v. which empties into the IJV.
The FACIAL V. IS VALVELESS & HAS COMMUNICATIONS WITH OTHER VEINS WHICH ARE CLINICALLY IMP. BECAUSE THEY PROVIDE ROUTES FOR THE SPREAD OF INFECTION. Recall that the angular v. communicates with the cavernous sinus via the two ophthalmic vv. The facial v. also communicates with the pterygoid plexus in the infratemporal fossa via the DEEP FACIAL V.

31. EXTERNAL NOSE

32. NOSE (SKELETON) Major alar cartilage Frontal Nasals Medial crus
Maxilla (frontal pr.)
Lateral crus
Septal cartilage
(lateral prs.)
Septal cartilage
Major alar cartilage
Lateral crus
Medial crus
The EXTERNAL NOSE has both a BONY & CARTILAGINOUS FRAMEWORK. The bones are the nasal, frontal and maxilla (frontal pr.). The cartilages are the septal , lat. nasal and gr. alar.
Alar fibrofatty
tissue
Septal cartilage
Alar fibrofatty tissue

33. EYELIDS &
LACRIMAL APPARATUS

34. EYELIDS (SAGITTAL SECTION)
Levator palpebrae superioris m.
Orbital septum
Sup. tarsal m.
Sclera
Sup. conjunctival fornix
Bulbar conjunctiva
Orbicularis oculi m. (palpebral pt.)
Palpebral conjunctiva
Sup. tarsus
Cornea
Tarsal glands
Sebaceous glands
Eyelashes (cilia)
1. The EYELIDS are fibromuscular folds that protect the eye and rest it from light.
(SKIP if already covered in orbit lecture). TWO MUSCLES insert into the sup. tarsal plate and serve to elevate the upper lid: 1) LEVATOR PALPEBRAE SUPERIORIS & 2) SUP. TARSAL M. The levator is a voluntary (skeletal) muscle innervated by the sup. division of III. The sup. tarsal m. is involuntary (smooth) and is innervated by postsynaptic sympathetic fibers. Their somata are in the sup. cervical ganglion. Paralysis of either muscle due to a lesion of III or the cervical part of the sympathetic trunk causes PTOSIS (drooping) of the upper lid.
The EYELIDS CONSIST OF FIVE LAYERS: 1) skin 2) subcutaneous tissue (loose, fluid can accumulate in this layer following injury) 3) muscular (palpebral part of orbicularis oculi) 4) tarsofascial (composed of the tarsal plates and orbital septum) and 5) palpebral part of conjunctiva. The SUP. & INF. TARSAL PLATES are composed of dense fibrous tissue and strengthen the lids. Embedded in their post. surfaces are tarsal gls.; the oily secretion of these glands "waterproofs" the eyelids and prevents them from sticking together when they close. The ducts of the tarsal gls. open onto the margins of the lids; sometimes they become obstructed. The ORBITAL SEPTUM is a membrane that stretches from the margins of the orbit to the tarsal plates. The PALPEBRAL PART OF THE CONJUNCTIVA is thick, red and vascular. It is examined in cases of suspected anemia. The palpebral conjunctiva is reflected off the eyelids onto the sclera of the eyeball where it becomes continuous with the bulbar conjunctiva . These lines of reflection are termed the sup. and inf. conjunctival fornices (singular is fornix). The thin space between the two layers of conjunctiva is the conjunctival sac (not labelled).
Openings of tarsal glands
Inf. tarsus
Orbicularis oculi m. (palpebral pt.)
Inf. conjunctival fornix
Orbital septum

35. TARSOFASCIAL LAYER OF EYELIDS
Orbital septum
Superior tarsus
Lat. palpebral lig.
Lacrimal sac
Inferior tarsus
Med. palpebral lig.
Orbital septum
The TARSOFASCIAL LAYER of the eyelids is well illustrated, as is the insertion of the aponeurosis of the levator palpebrae superioris. Note also the MED. & LAT. PALPEBRAL LIGS. The palpebral ligs. attach the tarsal plates to the margins of the orbit. Directly posterior to the med. palpebral lig. is the lacrimal sac --- the ligament is a useful guide to locating the sac in the laboratory.

36. LACRIMAL APPARATUS Sup. lacrimal papilla and punctum Orbital part of
lacrimal gland
Lacrimal canaliculi
Palpebral part of
lacrimal gland
Lacrimal sac
Ducts of
lacrimal gland
Nasolacrimal duct
Plica semilunaris
The LACRIMAL GLAND lies in the superolateral corner of the orbit. The gland secretes lacrimal fluid (tears) into the sup. fornix of the conjunctival sac via about 12 LACRIMAL DUCTS. Contraction of the orbicularis oculi closes the eyelids and spreads the lacrimal fluid over the eye to keep it moist. Excess fluid which reaches the lacrimal lake is drained by the lacrimal passages. Each eyelid bears a LACRIMAL PUNCTUM which is simply the opening of a tiny tube termed the LACRIMAL CANALICULUS. The two canaliculi pass medially and empty into the LACRIMAL SAC. The sac is blind superiorly but inferiorly it is continuous with the NASOLACRIMAL DUCT. The duct (membranous) passes inferiorly in the nasolacrimal canal (bony) to empty into the INFERIOR MEATUS OF THE NASAL CAVITY. (Now you know why you sniff when you cry). Inflammation of the lacrimal sac is termed DACRYOCYSTITIS ("dacryo" = tear, "cyst" = bladder).
Optional: 
PARALYSIS OF THE ORBICULARIS OCULI has serious consequences. The protective corneal reflex is lost (V1 afferent limb of reflex; VII efferent limb). The eye remains permanently open so that lacrimal fluid is not spread over it. The cornea drys out and can become ulcerated. The lower eyelid also "sags" and forms a pond where lacrimal fluid collects and then spills onto the face (EPIPHORA).
Opening of
nasolacrimal duct
(into inf. meatus
of nasal cavity)
Lacrimal caruncle
Inf. lacrimal papilla
and punctum

37. AUTONOMIC INNERVATION OF LACRIMAL GLAND
Trigeminal ganglion (V)
Greater petrosal n.
Maxillary n. (V2)
N. of pterygoid canal
Facial n. (VII)
Pterygopalatine ganglion
Pterygopalatinganglion
Sup. salivatory nucleus
Lacrimal gland
Deep petrosal n.
Int. carotid plexus
Sup. cervical sympathetic ganglion
Note key: Parasympathetics blue, sympathetics red; presynaptics solid, postsynaptics dashed.
PARASYMPATHETIC INNERVATION OF THE LACRIMAL GLAND involves a somewhat complex pathway. Presynaptic parasympathetic fibers leave the brain via VII. In the facial canal these fibers branch off and travel in the greater petrosal n. In the region of the f. lacerum the gr. petrosal n. joins another nerve to form the nerve of the pterygoid canal. The n. of the pterygoid canal runs anteriorly to reach the pterygopalatine fossa of the skull where the presynaptic parasympathetic fibers synapse in the pterygopalatine ganglion. From this ganglion postsynaptic parasympathetic fibers (should be shown as dashed blue line) are distributed to the lacrimal gland to stimulate secretion (the details of this part of the pathway are shown in the next plate).
Optional: 
SYMPATHETIC SUPPLY OF THE LACRIMAL GLAND is via postsynaptic fibers originating in the sup. cervical ganglion. They are inhibitory to the gland.
1st and 2nd thoracic spinal nn.
Sympathetic presynaptic fibers
Sympathetic postsynaptic fibers
Parasympathetic presynaptic fibers
Parasympathetic postsynaptic fibers

38. AUTONOMIC INNERVATION OF LACRIMAL GLAND (CONTINUED)
Communicating branch
Lacrimal gland
Lacrimal n.
Zygomaticotemporal n.
V ganglion
POSTSYNAPTIC PARASYMPATHETIC FIBERS TO THE LACRIMAL GLAND leave the pterygopalatine ganglion and join V2 (which lies just superior to the ganglion). The parasympathetic fibers immediately leave V2 via its zygomatic branch and enter the orbit. In the orbit the zygomatic n. communicates with the lacrimal n. (V1), thus completing the pathway (WHEW!).
Maxillary n. (V2)
Zygomatic n.
N. of pterygoid canal
Pterygopalatine ganglion
Pterygopalatine nn.

39. SCALP

40. S. C. A. L. P.
The SCALP CONSISTS OF FIVE LAYERS: 1) Skin 2) Connective tissue (containing the nerves and vessels of the scalp) 3) Aponeurosis (=galea aponeurotica) 4) Loose subaponeurotic tissue and 5) Pericranium. (Mnemonic: S. C. A. L. P. )
The first three layers of the scalp are intimately united and move as a unit on the fourth layer. The FOURTH LAYER is known as the DANGEROUS LAYER because infections can readily spread within it.

41. NERVES AND ARTERIES OF SCALP
The SCALP HAS A RICH NERVE SUPPLY. Included among the sensory nerves are branches from all three divisions of V, as well as branches from the ventral and dorsal rami of cervical nerves.
The SCALP HAS A RICH BLOOD SUPPLY. Direct branches from the ext. carotid a. (superficial temporal a., posterior auricular a., occipital a.) and indirect branches from the int. carotid a. (supratrochlear a., supraorbital a.) contribute. These arteries anastomose on the scalp and this is one reason why scalp lacerations bleed so heavily (another reason is that the dense connective tissue fibers in the second layer attach to the walls of the vessels and keep them open after they have been cut). Severe scalp wounds can result in a person bleeding to death ! Scalp lacerations are said to be the most common head injury requiring surgical care. The arteries of the scalp contribute little to the supply of the calvaria (mid. meningeal a. is chief supply). Hence scalp lacerations do not result in necrosis of the cranial bones. Surgical incisions in the scalp are made with the flaps remaining attached inferiorly (peripherally) so that the vessels and nerves are not cut as they enter the scalp from below.