Chapter 4 Head, Neck, and Dental Anatomy
REGIONS OF THE HEAD
Regions of the head include frontal, parietal, occipital, temporal, orbital, nasal, infraorbital, zygomatic, buccal, oral, mental regions. Specific landmarks are noted for each region.
• A. Frontal region: supraorbital ridge under each eyebrow; frontal eminence forms the prominence of the forehead.
D. Orbital region: includes eyeball and supporting structures within orbit (bony socket):
1. Lateral canthus: outer corner where upper and lower eyelids meet; medial canthus: inner corner of eye.
2. Upper and lower eyelids: cover and protect each eyeball; lacrimal gland: located behind each upper eyelid and within orbit and produces lacrimal fluid (tears).
F. Infraorbital region: inferior to orbital region and lateral to nasal region; zygomatic region overlies cheekbone; buccal region is composed of soft tissues of cheek:
G. Oral region: includes lips, oral cavity, palate, tongue, floor of mouth, parts of pharynx:
1. Nasolabial sulcus: groove running upward between labial commissure and ala of nose; labiomental groove: horizontal groove to which lower lip extends and which separates lower lip from chin in mental region.
H. Mental region: chin’s mental protuberance (prominence), with possible midline depression (dimple) that marks underlying bony fusion of lower jaw.
Oral Cavity
• See Chapters 2, Embryology and Histology: oral cavity histology; 3, Anatomy, Biochemistry, and Physiology: pharynx, digestion.
A. Structures labeled according to location: (1) lingual, if closest to tongue; (2) palatal, if closest to palate; (3) facial, if closest to facial surface; (4) buccal, if closest to inner cheek; (5) labial, if closest to lips.
B. Mucous membranes (oral mucosa): line inner oral cavity; parts of the lips are lined by labial mucosa; buccal mucosa lines inner cheek, covers buccal fat pad, including parotid papilla, and contains a duct opening from parotid salivary gland.
C. Maxillary and mandibular bones (jaws): lie beneath the respective lips and contain primary and/or permanent teeth, including incisors, canines, premolars, molars, depending on dentition present.
1. Maxillary and mandibular vestibules: upper and lower spaces between cheeks, lips, and gingival tissues.
2. Alveolar mucosa: lines each vestibule and meets labial or buccal mucosa at the mucobuccal fold (depth or height is location for local anesthetic nerve injections given into soft tissue).
D. Palate (roof of mouth):
E. Tongue (Figure 4-1):
2. Base: posterior one third, which attaches to floor of the mouth; does NOT lie within the oral cavity but rather in the oral part of pharynx.
3. Lateral surfaces: located on each side; dorsal surface is located on top and includes median lingual sulcus; ventral surface (underside) has visible deep lingual veins (varicosities in elderly) and plicae fimbriatae, with fringelike projections.
4. lingual papillae: elevated structures of specialized mucosa on tongue surface, some of which are associated with taste buds (see Chapters 2, Embryology and Histology; 3, Anatomy, Biochemistry, and Physiology: lingual papillae, taste sensation).
5. Sulcus terminalis: V-shaped groove located posteriorly on dorsal surface that separates base from body.
F. Floor of the mouth: located inferior to ventral surface of tongue (Figure 4-2):
G. Pharynx (throat): muscular tube that serves BOTH respiratory and digestive systems, divided into nasopharynx, oropharynx, laryngopharynx.
REGIONS OF THE NECK
A. Anterior region: corresponds to two anterior cervical triangles, separated by midline, and subdivided into submandibular and midline submental triangle by digastric muscle (Figure 4-3).
C. Thyroid cartilage: prominence of larynx at anterior midline; vocal cords (ligaments) are attached to posterior surface.
SKULL
Skull (22 bones), with single and paired bones. Immovable, with EXCEPTION of mandible and temporomandibular joint (TMJ). Has movable articulation with bony vertebral column in neck area. Contains bony openings for important nerves and blood vessels (Table 4-1). Has paranasal sinuses within that serve to lighten bony mass. Has many associated processes that are involved in important structures. To study its landmarks, important to view from superior, lateral, inferior, anterior. Its bones are divided into three categories: cranial, facial, hyoid, which are noted on each view; each category is discussed separately next.
A. Superior view of skull: major bones and sutures (joints between bones of the skull are immovable; fontanelles [“soft spots”] on an infant’s head).
B. Anterior view of skull: orbits and nasal cavity (Figure 4-4):
1. Orbits: contain and protect eyeballs:
a. Orbital walls: orbital plates of frontal, ethmoid, lacrimal; orbital surfaces of maxilla; zygomatic bone; and orbital surface of greater wing of sphenoid.
b. Orbital apex: lesser wing of sphenoid and palatine bones; optic canal is opening in orbital apex.
2. Nasal cavity: has piriform aperture for anterior opening; lateral boundaries are formed by maxillae:
a. Nasal septum: divides nasal cavity into two parts; formed by nasal septal cartilages, perpendicular plate of ethmoid bone, vomer.
C. Lateral view of skull (Figure 4-5):
1. Superior temporal line: superior ridge; inferior temporal line: superior boundary of temporal fossa; squamosal suture is between temporal and parietal bones.
2. Temporal fossa: formed by several bones of skull, contains body of temporalis; infratemporal fossa:inferior to temporal fossa; pterygopalatine fossa: deep to infratemporal fossa.
D. Inferior view of external surface of skull (Figure 4-6):
1. Hard palate: forms floor of nasal cavity and roof of mouth at anterior section; formed by palatine processes of maxilla and horizontal plates of palatine bones; bordered by alveolar process of maxilla and maxillary teeth (Figure 4-7).
2. Median palatine suture: midline articulation between palatine processes of maxillae anteriorly as well as horizontal plates of palatine bones posteriorly, noted clinically as the median palatal raphe, MORE prominent and thicker in the soft palate region; transverse palatine suture articulates with palatine processes of maxillae and horizontal plates of palatine bones.
Table 4-1 Bony openings in the skull and their associated nerves and blood vessels
| Bony opening | Bony location | Nerves and vessels |
|---|---|---|
| Carotid canal | Temporal | Internal carotid artery |
| Cribriform plate with foramina | Ethmoid | Olfactory nerves |
| External acoustic meatus | Temporal | (Opening to tympanic cavity) |
| Foramen lacerum | Sphenoid, occipital, temporal | (Cartilage) |
| Foramen magnum | Occipital | Spinal cord, vertebral arteries, eleventh cranial nerve |
| Foramen ovale | Sphenoid | Mandibular division of fifth cranial nerve |
| Foramen rotundum | Sphenoid | Fifth cranial nerve |
| Foramen spinosum | Sphenoid | Middle meningeal artery |
| Greater palatine foramen | Palatine | Greater palatine nerve and vessels |
| Hypoglossal canal | Occipital | Ninth cranial nerve |
| Incisive foramen | Maxilla | Nasopalatine nerve and branches of sphenopalatine artery |
| Inferior orbital fissure | Sphenoid and maxilla | Infraorbital and zygomatic nerves, infraorbital artery, ophthalmic vein |
| Infraorbital foramen and canal | Maxilla | Infraorbital nerve and vessels |
| Internal acoustic meatus | Temporal | Seventh and eighth cranial nerves |
| Jugular foramen | Occipital and temporal | Internal jugular vein and ninth, tenth, eleventh cranial nerves |
| Lesser palatine foramen | Palatine | Lesser palatine nerve and vessels |
| Mandibular foramen | Mandible | Inferior alveolar nerve and vessels |
| Mental foramen | Mandible | Mental nerve and vessels |
| Optic canal and foramen | Sphenoid | Optic nerve and ophthalmic artery |
| Petrotympanic fissure | Temporal | Chorda tympani nerve |
| Pterygoid canal | Sphenoid | Area nerves and vessels |
| Stylomastoid foramen | Temporal | Seventh cranial nerve |
| Superior orbital fissure | Sphenoid | Third, fourth, sixth cranial nerves and ophthalmic nerve and vein |
From Fehrenbach MJ, Herring SW: Illustrated anatomy of the head and neck, ed 3, St. Louis, 2007, Saunders/Elsevier.
Figure 4-4 Anterior view of skull.
(From Fehrenbach MJ, ed: Dental anatomy coloring book, St. Louis, 2008, Saunders/Elsevier.)
Figure 4-5 Lateral view of skull.
(From Fehrenbach MJ, ed: Dental anatomy coloring book, St. Louis, 2008, Saunders/Elsevier.)
Figure 4-6 Inferior view of external surface of skull.
(From Fehrenbach MJ, ed: Dental anatomy coloring book, St. Louis, 2008, Saunders/Elsevier.)
Figure 4-7 Inferior view of hard palate.
(From Fehrenbach MJ, ed: Dental anatomy coloring book, St. Louis, 2008, Saunders/Elsevier.)
Figure 4-8 Superior view of internal surface of skull.
(From Fehrenbach MJ, ed: Dental anatomy coloring book, St. Louis, 2008, Saunders/Elsevier.)
Cranial Bones
A. Occipital: single that is located in MOST posterior part of skull:
1. Foramen magnum on external surface: largest skull opening; carries spinal cord, vertebral arteries, accessory nerve.
B. Frontal: single that forms forehead and superior part of orbits:
D. Temporal bones: paired and form lateral walls of skull:
E. Sphenoid (“butterfly”): single in midline; MOST complex; articulates with frontal, parietal, ethmoid, temporal, zygomatic, palatine, occipital bones, maxillae, vomer:
1. Foramen ovale: oval opening that carries mandibular division of fifth cranial nerve (trigeminal); foramen rotundum: round opening that carries maxillary division of the same nerve; foramen spinosum: near spine and carries middle meningeal artery into cranial cavity.
2. Body: middle position; contains sphenoidal sinus, which communicates with and drains into nasal cavity through opening superior to each superior nasal concha:
Facial Bones
A. Vomer: single that forms posterior part of nasal septum; located in midsagittal plane, inside nasal cavity; has free posteroinferior border.
B. Smaller bones (but they do just fine unless they participate in any bar fights!):
1. Lacrimal: paired that form small part of anterior medial wall of orbit; nasolacrimal duct is formed at junction of lacrimal and maxillary bones; lacrimal fluid from gland drains into inferior nasal meatus.
C. Zygomatic: paired that form cheek bones (malar surfaces), each composed of frontal, temporal, maxillary processes:
D. Palatine: paired that consist of horizontal and vertical plates; articulate with each other and with maxillae and sphenoid:
E. Maxilla: upper jaw, consists of two maxillary bones (maxillae) fused together; articulates with frontal, lacrimal, nasal, inferior nasal concha, sphenoid, ethmoid, palatine, zygomatic bones, vomer (Figure 4-9); each maxilla has a body and frontal, zygomatic, palatine, alveolar processes:
1. Body of maxilla contains maxillary sinus located just posterior to maxillary canine and premolars; largest sinus; drains into middle meatus.
2. Inferior orbital fissure: separates each orbital surface from sphenoid; carries infraorbital and zygomatic nerves, infraorbital artery, inferior ophthalmic vein.
3. Infraorbital sulcus groove in floor of orbital surface: becomes infraorbital canal, then terminates as infraorbital foramen; carries infraorbital vessels.
4. Canine fossa: depression posterosuperior to maxillary canine roots; canine eminence is facial ridge over maxillary canine.
5. Lateral wall of nasal cavity: made up mainly of maxilla; floor of nasal cavity is formed by palatine process of maxilla anteriorly, also anterior part of hard palate.
F. Mandible: lower jaw, single, ONLY freely movable bone of skull; articulates with temporal bones at each TMJ (Figure 4-10):
1. Mental protuberance: prominence of chin; mandibular symphysis is ridge where bone was formed by fusion.
2. Mental foramen: on outer (lateral) surface of mandible, between apices of mandibular premolars; allows entrance of mental nerve and blood vessels into mandibular canal.
3. Mandibular foramen: on inner (medial) surface of ramus, from which inferior alveolar vessels exit mandible after traveling in mandibular canal.
4. Lingula: sharp spine that overhangs mandibular foramen and gives attachment to the sphenomandibular ligament; at its lower and back part is a notch from which the mylohyoid groove runs obliquely downward and forward and lodges the mylohyoid vessels and nerve.
5. Alveolar process: contains roots of the mandibular teeth; ramus extends upward and backward from the body on each side and terminates in coronoid process and coronoid notch.
7. External oblique line (ridge): outer crest where ramus joins the body; ramus extends from angle to condyle and articulates with TMJ; mandibular notch is located between coronoid process and condyle.
MUSCLES OF HEAD AND NECK
Cervical Muscles
Cervical muscles include SCM and trapezius.
A. The SCM: paired that serves as MAIN muscular landmark, divides neck region into anterior and posterior cervical triangles (Figure 4-3):
MUSCLES OF FACIAL EXPRESSION
Muscles of facial expression act in various combinations to alter appearance of face; innervated by the facial nerve, seventh (VII) cranial nerve (Figure 4-11).
A. Epicranial muscle (epicranius), located in scalp region, with frontal and occipital bellies, which are separated by a scalp tendon, epicranial aponeurosis; raises eyebrows and scalp to express surprise.
C. Corrugator supercilii is deep to superior part of orbicularis oculi muscle; originates on frontal bone and inserts into skin tissue of eyebrow; causes vertical wrinkles in forehead (frowning).
D. Buccinator forms anterior part of cheek; originates from alveolar processes of maxilla, mandible, and pterygomandibular raphe (ligament that extends from hamulus and attaches to mylohyoid line); pulls angle of mouth laterally and shortens cheek BOTH vertically and horizontally; keeps food in CORRECT position during chewing.
E. Risorius originates from fascia superficial to masseter and inserts in skin tissue at angle of mouth; widens mouth to stretch lips.
F. Levator labii superioris originates from infraorbital region of maxilla and inserts in skin tissue of upper lip; raises upper lip.
G. Levator labii superioris alaeque nasi originates from frontal process of maxilla and inserts into skin tissue of ala of nose and upper lip; raises upper lip and dilates ala of nose for sneering.
H. Zygomaticus major originates from zygomatic bone and inserts in skin tissue at angle of mouth; raises angle of upper lip and pulls it laterally; zygomaticus minor originates on zygomatic bone and inserts in skin tissue of upper lip; raises upper lip for smiling.
I. Levator anguli oris originates superior to root of maxillary canine teeth and inserts in skin tissues at angle of mouth; raises angle of mouth; depressor anguli oris originates on mandible and inserts in skin tissue at angle of mouth; lowers angle of mouth for smiling and then frowning.
J. Depressor labii inferioris originates from mandible and inserts in skin tissues of lower lip; lowers lower lip.
K. Mentalis originates near mandible midline and inserts in skin tissue of chin; raises chin, causing lower lip protrusion and narrowing of oral vestibule.
L. Platysma runs from the neck to the mouth, covering anterior cervical triangle; originates in skin tissue superficial to the clavicle and shoulder and inserts on mandible and muscles surrounding mouth; raises skin of the neck and pulls down the corner of mouth (making anyone a Mr. Grimace, so stretch it out now as you study anatomy).
Figure 4-11 Muscles of facial expression.
(From Fehrenbach MJ, ed: Dental anatomy coloring book, St. Louis, 2008, Saunders/Elsevier.)
Muscles of Mastication
Muscles of mastication are paired muscles that attach to mandible and work with TMJ to accomplish movements of mandible: depression, elevation, protrusion, retraction, lateral deviation (Figures 4-12 and 4-13). Innervated by mandibular division of fifth (V) cranial nerve (trigeminal). Include masseter, temporalis, medial pterygoid, lateral pterygoid. Involved in temporomandibular joint disorder (TMD). See later discussion on occlusion in regard to masseter.
A. Masseter: MOST superficially located and one of strongest muscles; located anterior to parotid gland:
C. Medial pterygoid: SIMILAR to but deeper to masseter:
D. Lateral pterygoid: two separate heads of origin, superior and inferior, separated by slight interval anteriorly; heads fuse posteriorly, within infratemporal fossa, deep to temporalis:
Hyoid Muscles
Hyoid muscles are located superficially in neck tissues, attached to hyoid. Assist in the actions of mastication and swallowing (Figure 4-14).
A. Suprahyoids: paired that are located superior to hyoid:
1. Act to raise hyoid and larynx by contraction of muscles of mastication when mandible is stabilized, which occurs during swallowing.
2. Contraction of anterior muscles causes mandible to lower and jaws to open when hyoid is stabilized by contraction of both posterior suprahyoid and infrahyoid muscles.
3. Categorized according to anterior or posterior position relative to hyoid:
a. Digastric: anterior and posterior bellies (separate); anterior belly is part of anterior suprahyoids; posterior belly is part of posterior suprahyoids:
(1) Each muscle demarcates superior part of anterior cervical triangle, forming (with the mandible) submandibular triangle on each side of neck.
(2) Right and left anterior bellies form midline submental triangle; anterior belly arises from intermediate tendon and inserts close to symphysis on inner surface of mandible, and posterior belly arises from mastoid process and inserts on intermediate tendon; anterior belly innervated by mylohyoid nerve; posterior belly innervated by posterior digastric nerve.
b. Mylohyoid: located deep to the digastric; its fibers run transversely between the two sides of mandible, where it originates from mylohyoid line (on inner surface of mandible):
B. Infrahyoids: paired that are located inferior to hyoid; innervated by second and third cervical nerves; generally act to lower hyoid unless indicated:
1. Sternothyroid: superficial to thyroid gland, deep and medial to sternohyoid; originates from sternum and inserts on thyroid cartilage and lowers thyroid cartilage and larynx; does NOT directly lower hyoid.
2. Sternohyoid: superficial to sternothyroid, thyroid, cartilage; originates from sternum and inserts on hyoid.
TEMPOROMANDIBULAR JOINT
Temporomandibular joint (TMJ) is located on each side of the head and allows movement of the mandible for speech and mastication (Figure 4-15). Innervated by mandibular division of fifth cranial nerve (trigeminal) and blood supply from the external carotid artery. Patients may experience a temporomandibular joint disorder (TMD) of one or BOTH of these joints. Bones of the TMJ are discussed in skeletal system section.
A. Joint capsule: completely encloses TMJ; membranes that line inside of joint capsule secrete synovial fluid, which helps lubricate joint.
B. Disc: located between temporal bone and condyle, completely divides the TMJ into two synovial cavities, upper and lower, filled with synovial fluid:
1. Attached to mandibular condyle anteriorly and NOT to temporal bone, except indirectly through capsule.
C. Ligaments associated with TMJ:
1. TMJ ligament: on lateral side of each joint and reinforced capsule; prevents excessive retraction of mandible.
CLINICAL STUDY
| Age | 58 YRS | SCENARIO |
| Sex |  Male  Female |
The first afternoon patient has not had a dental examination since her last dentist retired 2 years ago. An initial extraoral examination indicates that her zygomatic region is fi rm and enlarged; she currently has no pain or discomfort in the jaw area. She does admit to frequently grinding her teeth at night. |
| Height | 5′6″ | |
| Weight | 75 LBS | |
| BP | 115/68 | |
| Chief Complaint | “My jaws really ache when I wake up.” | |
| Medical History |
1. What caused the patient’s firmly enlarged zygomatic region? Why is there no jaw discomfort except in the morning?
2. Does the condition of cheek firmness and enlargement require treatment? If so, what may be recommended?
1. Patient’s firm zygomatic region and enlarged cheeks are caused by an overuse of masseter muscle with grinding during sleep. The muscle underwent hypertrophy (enlargement by increase in size of cells, not number of cells). Jaw discomfort that is a dull ache only upon awakening is indicative of nighttime bruxism (grinding) and/or clenching habit. That is why there is no pain, since now she is at an afternoon appointment.
2. Her teeth should be checked for the presence of occlusal wear (attrition) and cusp fracture. The condition may require noninvasive treatment initially with a flat-plane splint (mouthguard), which prevents full closure and allows the masseter muscle to relax. It also helps distribute forces and prevent further wear to the occlusal surfaces of the teeth.
ARTERIAL BLOOD SUPPLY OF THE HEAD AND NECK
B. Common carotid:
1. Branchless and travels up the neck, lateral to the trachea and larynx, then to thyroid cartilage.
C. Internal carotid:
D. External carotid:
3. Anterior branches of external carotid:
a. Superior thyroid branches into infrahyoid, sternocleidomastoid, superior laryngeal, and superior and inferior thyroid arteries, which supply tissues inferior to hyoid, including infrahyoid muscles, SCM, muscles of larynx, thyroid gland.
b. Lingual arises above superior thyroid, at level of hyoid; travels anteriorly to tongue apex; supplies tissues superior to hyoid, including suprahyoid muscles and floor of mouth by the dorsal lingual, deep lingual, sublingual, suprahyoid branches; also supplies tongue.
c. Sublingual supplies mylohyoid muscle, sublingual gland, floor of mouth; suprahyoid branch supplies suprahyoid muscles.
d. Facial arises slightly superior to lingual as it branches off anteriorly and has a complicated path; supplies the face in the oral, buccal, zygomatic, nasal, infraorbital, orbital regions with its major branches, including ascending palatine, submandibular and submental, inferior labial, superior labial, angular (may share common trunk with lingual).
4. Medial branch of external carotid includes ascending pharyngeal artery and pharyngeal and meningeal branches.
6. Terminal branches of external carotid:
a. Superficial temporal arises within parotid gland and may be clinically visible in temporal region; transverse facial branch supplies parotid; middle temporal branch supplies temporalis; frontal and parietal branches supply scalp.
b. Maxillary gives off many branches within infratemporal and pterygopalatine fossae, such as middle meningeal and inferior alveolar arteries, and has branches near the muscles supplied, including deep temporal, pterygoid, masseteric artery, and buccal muscles, then branches into inferior alveolar (IA), posterior superior alveolar (PSA), infraorbital (IO), greater (GP) and lesser palatine (LP) (Figure 4-16).
c. The IA arises from maxillary artery in infratemporal fossa, turns inferiorly to enter mandibular foramen, then enters mandibular canal and IA, branches into mylohyoid before it enters the canal; in canal, branches into mandibular posterior and alveolar (dental) branches to supply teeth, periodontium, and associated gingiva.
d. Mylohyoid arises before main artery enters mandibular canal by way of mandibular foramen and travels in the mylohyoid groove to supply floor of mouth and mylohyoid.
e. Mental arises from main artery and then exits mandibular canal by way of mental foramen to supply the chin tissues; anastomoses with inferior labial artery.
f. Incisive branches off main artery and remains in mandibular canal, divides into dental branches to supply mandibular anteriors and alveolar branches to supply periodontium; anastomoses with alveolar branches of incisive artery on other side of mouth.
g. The PSA artery is given off just as maxillary artery leaves infratemporal fossa and enters pterygopalatine fossa, enters PSA foramina, and gives off dental branches (to supply the maxillary posteriors) and alveolar branches (to supply periodontium and maxillary sinus); anastomoses with anterior superior alveolar artery.
h. The IO artery branches from the maxillary in the pterygopalatine fossa and may share common trunk with the PSA artery; enters orbit through the inferior orbital fissure and travels through the IO canal; gives off orbital branches to the orbit; gives off anterior superior alveolar (ASA).
i. The ASA arises from IO artery and gives off dental branches to supply the maxillary anteriors and alveolar branches to supply periodontium; anastomoses with the PSA; after giving off these branches in infraorbital canal orbit, emerges onto the face from IO foramen to IO region of face; anastomoses with facial.
VENOUS DRAINAGE OF THE HEAD AND NECK
Veins are symmetrically located but have greater variability in location than do arteries. Veins anastomose freely and generally are larger and MORE numerous than arteries in same tissue. Internal jugular drains brain and other tissue; external jugular drains only some extracranial tissues, with many anastomoses between them. Internal and external jugular are major venous drainage vessels of head and neck (Figure 4-17). Leaving the head near the base of neck, veins become larger. Vascular system is capable of spreading infection or cancerous cells in head and neck area because valveless veins control direction of blood flow.
A. Facial: includes superior labial, inferior labial, submental, lingual; drains into internal jugular:
1. Begins at medial canthus, at junction of supratrochlear and supraorbital, which anastomoses with ophthalmic that drains orbit tissues and provides communication with cavernous venous sinus.
2. Receives branches from same facial areas supplied by facial artery and anastomoses with deep veins, such as the pterygoid plexus in infratemporal fossa and retromandibular vein, before joining internal jugular vein at level of hyoid.
3. Has oral tributaries:
c. Lingual, including dorsal lingual, which drains dorsal surface of tongue; deep lingual veins, which drain ventral surface; and sublingual veins, which drain floor of the mouth; may join to form a single vessel or may empty into larger vessels separately, either indirectly into facial or directly into internal jugular.
B. Retromandibular:
1. Formed by union of superficial temporal and maxillary; emerges from parotid; drains areas similar to those supplied by superficial temporal and maxillary arteries.
2. Divides below parotid; anterior division joins facial, and posterior division continues and is then joined by posterior auricular vein, which drains scalp behind ear and becomes external jugular:
a. Superficial temporal drains lateral scalp; drains into and forms retromandibular, along with maxillary.
C. Pterygoid plexus of veins:
1. Collection of small anastomosing vessels around pterygoid muscles and surrounding maxillary artery, protecting it from compression in infratemporal fossa; drains blood from maxillary and middle meningeal veins, which drain blood from meninges and deep facial parts.
2. Anastomoses with BOTH facial and retromandibular veins; may be involved in spread of infection to cavernous venous sinus (needletrack infections); also drains PSA vein, formed by union of dental branches of maxillary teeth and alveolar branches of periodontium.
GLANDULAR TISSUE
Glandular tissues include the lacrimal, salivary, thyroid, parathyroid, thymus glands.
• See Chapters 6, General and Oral Pathology: glandular diseases or conditions; 9, Pharmacology: secretions.
A. Lacrimal glands:
B. Salivary glands (Figure 4-18):
1. Produce saliva, which lubricates and cleanses oral cavity and aids digestion; include BOTH major and minor glands, defined by their size; exocrine glands with ducts that drain saliva directly into oral cavity where it is used; controlled by ANS.
2. With connective tissue of gland divided into capsule, which surrounds outer part, and septa (plural of septum), each septum helps divide inner part of the gland into larger lobes and smaller lobules.
3. Major glands are large paired glands; ducts are named after them; include parotid, submandibular, sublingual.
4. Parotid:
a. Largest encapsulated gland; provides only 25% of total volume; has purely serous secretion; divided into two lobes: superficial and deep.
b. Parotid duct (Stensen’s), which emerges from anterior border of gland, pierces buccinator, then opens into oral cavity at parotid papilla; occupies parotid fascial space, posterior to ramus, anterior and inferior to the ear; extends irregularly from zygomatic arch to angle of mandible.
c. Innervated by parasympathetic nerves of the otic ganglion of ninth cranial nerve (glossopharyngeal), as well as afferent nerves from auriculotemporal branch of the fifth cranial nerve (trigeminal); drains into deep parotid nodes; supplied by branches of external carotid artery.
d. Becomes enlarged and tender with mumps (unilateral or bilateral parotitis, inflammation of gland), viral disease that because of introduction of a vaccine is NOT a common childhood disease; the salivary gland MOST commonly involved in tumorous growth, which can change consistency and cause unilateral facial pain on involved side (seventh [VII] cranial nerve [facial] travels through gland).
e. Trauma can also occur to nerve from accidental overreaching of needle during inferior alveolar nerve block, causing unilateral transient facial paralysis, temporary loss of movement of muscles of facial expression on affected side; patient CANNOT close one eye, smiles asymmetrically, has drooping lip on that side.
5. Submandibular:
b. Submandibular duct (Wharton’s), which arises from deep lobe and remains inside mylohyoid, travels along anterior floor of the mouth and then opens into oral cavity at the sublingual caruncle; tortuous travel may be reason that it is gland MOST often involved in stone formation.
6. Sublingual:
b. NOT just one major duct; sublingual ducts (Bartholin’s) open directly into oral cavity through gland and have other ducts that open along the sublingual fold; located in sublingual fossa in sublingual fascial space at the floor of the mouth; superior to mylohyoid, medial to body of mandible, anterior to submandibular.
7. Minor salivary glands:
a. Smaller than major glands but MORE numerous, exocrine glands with unnamed ducts that are shorter than major glands; scattered in buccal, labial, and lingual mucosa, soft palate, lateral parts of hard palate, floor of the mouth; include von Ebner’s glands (associated with circumvallate lingual papillae).
8. Histology of salivary glands:
C. Thyroid gland (Figure 4-19):
1. Located in anterior and lateral regions of neck, inferior to thyroid cartilage, at junction between larynx and trachea.
3. LARGEST endocrine gland; has NO ducts but is encapsulated; consists of two lateral lobes, right and left, connected anteriorly by isthmus.
D. Parathyroid glands (Figure 4-19):
1. Located close to or inside thyroid on posterior surface; consist of four endocrine glands, two on each side, with NO ducts; produce parathyroid hormone secreted directly into blood to regulate calcium and phosphorus levels.
E. Thymus gland:
1. Ductless endocrine gland located in thorax and anterior region of base of neck, inferior to thyroid, deep to sternum; its muscles, superficial and lateral to trachea, consist of two lateral lobes in close contact at midline.
2. Part of immune system and fights disease process; T-cell lymphocytes mature in gland in response to stimulation by thymus hormones.
CLINICAL STUDY
| Age | 49 YRS | SCENARIO |
| Sex |  Male  Female |
The intraoral examination of the patient reveals a number of carious lesions, and the oral mucosa appears quite dry. |
| Height | 6′5″ | |
| Weight | 175 LBS | |
| BP | 112/62 | |
| Chief Complaint | “My mouth is so sore when I eat!” | |
| Medical History | Recent radiation therapy for low-grade adenoid cystic carcinoma of the submandibular gland after surgical removal | |
| Current Medications | None | |
| Social History |
1. What is the cause of the patient’s dry mouth? What type of tumor is this? Why is the patient not taking any medications?
1. Primary cause of xerostomia is radiation treatment the patient received for tumor. Radiation treatment causes glandular tissue fibrosis or atrophy, resulting in partial or total loss of secretory function of the submandibular salivary gland (hypofunction). Submandibular is the second largest encapsulated gland; provides 60% to 65% of total saliva volume with mixed secretion, thus most of the volume of saliva. Discomfort and difficulty speaking and swallowing are common complaints of those suffering from inadequate saliva production. Adenoid cystic carcinoma (ACC) is uncommon except in salivary glands, is usually a painless, slow-growing mass, and often appears to be a low-grade tumor; hard to get rid of completely and very often comes back after surgery. There is no effective medication or chemotherapy for this type of tumor.
2. Patient may use salivary substitute throughout the day to provide moisture for the mouth when speaking and swallowing. Sipping water frequently, sucking on sugar-free lozenges, and humidifying air in the home have also been found to be beneficial. Daily use of mineralizing fluoride and calcium product helps prevent formation of caries.
3. Secretory cells that make up submandibular glands are serous and mucous cells, since it is a mixed gland, and both types of cells can be damaged by radiation treatment. Gland occupies submandibular fossa in submandibular fascial space, mostly superficial to the mylohyoid; deep lobe wraps around the posterior part and is posterior to the sublingual.
TRIGEMINAL NERVE AND SENSORY ROOT
Trigeminal nerve (fifth cranial nerve [V]) is formed by ophthalmic, maxillary, mandibular branches.
• See Chapters 3, Anatomy, Biochemistry, and Physiology, and 14, Pain Management: nervous system, oral cavity nerves; 6, General and Oral Pathology: trigeminal neuralgia.
A. Ophthalmic division (ophthalmic nerve, V1) is FIRST and smallest division, carried by way of superior orbital fissure; includes frontal, lacrimal, nasociliary.
B. Maxillary division (maxillary nerve, V2) of fifth cranial nerve (trigeminal) (Figure 4-20):
1. Second division of trigeminal, with nerve trunk formed in pterygopalatine fossa by convergence of MANY nerves; enters skull through foramen rotundum; contains branches: zygomatic, infraorbital (IO), anterior superior alveolar (ASA), middle superior alveolar (MSA), posterior superior alveolar (PSA), greater palatine (GP), lesser palatine (LP), nasopalatine (NP).
2. Zygomatic: union of zygomaticofacial and zygomaticotemporal in orbit and is afferent; conveys postganglionic parasympathetic fibers to lacrimal gland; courses posteriorly along lateral orbit floor, enters pterygopalatine fossa through inferior orbital fissure, then joins maxillary.
3. The IO: passes into IO foramen; then travels through IO canal, along with infraorbital blood vessels; then joined by ASA, which is afferent and is formed by a union of cutaneous branches from the upper lip, medial part of cheek, lower eyelid, side of nose; then passes from IO canal and groove into pterygopalatine fossa through inferior orbital fissure; after leaving IO groove, and within pterygopalatine fossa, receives PSA.
4. The ASA: ascends along anterior wall of maxillary sinus to join IO in IO canal; afferent for maxillary anteriors by way of dental and interdental branches; forms dental plexus and innervates overlying facial gingiva; crossover can occur over midline.
5. The MSA: afferent for maxillary premolar teeth and possibly mesial buccal (MB) root of maxillary first molar; originates from dental, interdental, interradicular branches, forming dental plexus; then ascends to join IO by running in lateral wall of maxillary sinus and communicates with BOTH the ASA and PSA; may or may not be present; if NOT present, area is innervated by BOTH the ASA and PSA, but MAINLY the ASA.
6. The PSA joins IO (or maxillary directly) in the pterygopalatine fossa; afferent for most parts of maxillary molar teeth (possibly NOT MB root of maxillary first molars) and maxillary sinus:
7. Greater palatine (GP, anterior palatine): located between mucoperiosteum and bone of anterior hard palate; communicates with terminal fibers of nasopalatine (NP):
a. Enters GP foramen in palatine bone to travel in pterygopalatine canal, along with GP blood vessels and lesser palatine (LP) and blood vessels, ascends through pterygopalatine canal, toward maxillary nerve in pterygopalatine fossa; afferent for posterior hard palate and posterior lingual gingiva.
b. The LP (posterior palatine): afferent for soft palate and palatine tonsillar tissues; enters LP foramen in the palatine bone, along with LP blood vessels; then joins GP nerve and blood vessels in pterygopalatine canal; then ascends through pterygopalatine canal toward maxillary nerve in pterygopalatine fossa.
C. Mandibular division (mandibular nerve, V3) of fifth cranial nerve (trigeminal) (Figure 4-21):
1. Largest of three divisions that form trigeminal and innervates ALL muscles of mastication:
a. Has meningeal and muscular branches, which arise from trunk before separation into two trunks; main trunk is formed by union of anterior and posterior trunks in infratemporal fossa, before passing through foramen ovale; muscular branches arise from motor root of trigeminal; have deep temporal nerves that are efferent for temporalis and include masseteric nerve, which is efferent for masseter, and sensory branch to TMJ and lateral pterygoid nerve, which is efferent for lateral pterygoid.
b. Anterior trunk formed by union of buccal nerve and muscular branches; posterior formed by union of auriculotemporal, lingual, inferior alveolar (IA); mandibular division joins ophthalmic and maxillary to form trigeminal ganglion; includes buccal, muscular, lingual, IA, mental, incisive, mylohyoid, and auriculotemporal, which is efferent for the external ear and scalp; then joins posterior trunk.
2. Buccal (long buccal): not to be confused with buccal nerve that serves the buccinator muscle of the cheek:
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