Surgical Anatomy of the Head and Neck PDF

Michael D.Maves Anatomy isthe basic science of all surgery. Surgery in the region of the head and neck cannot be considered safe unless the surgeon thoroughly understands the anatomy of this area and its important variations. Although ana- tomic structures and the relations between them do not...

Michael D.Maves Anatomy isthe basic science of all surgery. Surgery in the region of the head and neck cannot be considered safe unless the surgeon thoroughly understands the anatomy of this area and its important variations. Although ana- tomic structures and the relations between them do not change. our knowledge of anatomy must be continually updated to meet the challenge of new surgical techniques and approaches. This chapter isan overview of the surgical anatomy of the head and neck with afocus on the major regions. Itisnot asubstitute for thorough anatomic knowl- edge, which can be gained only through intensive study in acadaver laboratory and an operating room. THE CRANIUM Scalp The cranium iscovered by the hair-bearing scalp, which is divided into layers of skin and subcutaneous tissue, galea aponeurotica, loose connective tissue, and periosteum or pericranium covering the calvarial vault. The blood sup- ply of the scalp comes from the paired supraorbital and supratrochlear arteries anteriorly, the terminal branches of the superficial temporal arteries laterally, and the occipital vessels posteriorly. This rich vascularity provides anetwork on which small scalp flaps can be based and rotated, as in the management of male pattern baldness. Sensation to the scalp isprovided by branches of cranial and spinal nerves. Calvaria The bony vault of the cranium, the calvaria, consists of the unpaired frontal bone, the paired parietal bones, and the unpaired occipital bone (Fig. 1.1 ).In the lateral aspect, the greater wing of the sphenoid bone and the tem- poral bone complete the cranium. There isarich layer of diploic bone between the inner and outer tables of the calvaria. This isasource for split-thickness calvarial bone grafts, which often are used in head and neck reconstruc- tion. The calvarium isthickest atthe external occipital pro- tuberance and in the parietal region. Itisthinnest over the temporal region. This allows ready access for neurotologic operations on the middle fossa. The venous circulation of the calvaria is provided by diploic veins, which drain to the veins of the scalp or into the dural venous sinuses. In some instances, the diploic veins are connected to each other, and this communication allows osteomyelitis that originates in the frontal sinus to involve the frontal bone, scalp, and dura. CRANIAL FOSSAE The intracranial cavity isroughly divided into three fossae. The anterior or frontal cranial fossa contains the paired frontal lobes and provides access to the nasal cavity for the olfactory nerves through the cribriform plate. The crista galli provides superior midline extension of the nasal sep- tum. The middle cranial fossa contains the temporal lobes. In this important junction of the cranial cavity, the middle meningeal artery arises from the foramen spinosum, and the trigeminal nerve enters through the superior orbital fis- sure (Vl), the foramen rotundum (V2), and the foramen ovale (V3). Cranial nerves II, III, N, and VI, which traverse the cavernous sinus and enter the orbit. also course through the middle cranial fossa. The internal carotid artery is in its place in the carotid siphon as ittraverses the cavernous sinus in this region. The posterior cranial fossa contains the paired cerebellar hemispheres and the brainstem. In this location, the internal auditory meatus is associated with the seventh and eighth cranial nerve complex. The jugular foramen, transverse sinus, and foramen magnum are the major landmarks of the posterior cranial fossa. 3 4 Sec:tion 1:Basic Science/General Medicine A B Figure 1.1 Scalp, cranium, and intracranial cavity. A; 1, Coronal suture; 2, superior temporal line; 3, inferior temporal line; 4, cs parietale; 5, squamous suture; 6, pariatomanoid suture; 7, lamb- doid suture; 8,occipital bone; 9, occipitomastoid suture; 10, manoid process; 11, external acous- uc meatus; 12, styloid process; 13, condyle of mandible; 14, coronoid process of mandible; 15, body of mandible; 16, mental foramen; 17, zygomatic bone; 18, infraorbital foramen; 19, fromal process (maxilla}; 20, anterior nasal spine; 21, nasal bone; 22, lacrimal bone; 23, orbital lamina of ethmoid bene; 24, glabella; 25, sphenoid bone; 26, pterion; Zl, temporal bone. B: 1,Sphenoid bone; 2, frontal bone; 3, anterior cranial fossa; 4, anterior dinoid procass; 5, caroud sulcus; 6, mid- dle cranial fossa; 7, petrous portion of temporal bone; 8, lnmrnal acoustic meatus; 9, Jugular foramen; 10, mastoid foramen; 11, hypoglossal canal; 12, foramen magnum; 13, posterior cranial fossa; 14, sulcus fer greater and lesser petrosal nerves; 15, foramen spincsum; 16, foramen ovale; 17, foramen laa~rum; 18, foramen rotundum; 19, superior orbital flssure; 20, optic canal; 21, anterior ethmoidal foramen; 22, anterior ethmoidal foramen; 23, foramen a~cum. EYELID, ORBIT, AND EYE Eyelids 1he upper and lower eyelids are similar in structure, although the upper eyelid is more mobile and has fea- tures not found in the lower eyelid. The space between the eyelids isknown as the palpebral :fissure, which islimited medially and laterally by the canthi. At the medial canthus isthe lacrimal caruncle, where there isasmall lake of tears and the tiny papillae of the lacrimal duct system. The con- junctiva isathin mucous membrane layer that covers the inner aspects of the eyelids and mends onto the surface of the globe. Tarsus The upper ta:ml plate provides rigidity to the upper ~­ lid and isl;uger than the lower tarsus (Fig. 1.2). Each~­ lid consists (from without inward) of skin, subcutaneous ti.uue, 'VOluntaiy muscle of the Oibicularis oculi. orbital septum, tarsus, smooth muscle, and conjunctiva. The more freely mobile upper lid receives the insertion of the le¥ator palpebrae superioris muscle. The orbicularis oculi is the sphincteric muscle of the upper and lower eyelids. It attaches at amedial palpebral ligament and spreads in an arc laterally and inferiorly to provide asphincteric muscle to the eye. Itreceives in.n.emltion from the tempo- ral and zygomatic branches of the facial nerve. This muscle inteidigitates with the frontalis muscle and the corrugator supercilii. Blood Supply 1he arterial supply of the eyelids isprovided by the angu- lar branch of the facial artery, which forms an anastomotic network with the supraorbital and supratrochlear artery and shares asmall contribution from the superficial tem- poral vessels. The veins of the eyelids are larger and more numerous than the arteries and drain into the ophthalmic and angular veins medially and the superficial temporal vein laterally. Accompanying the peripheral arterial arcade of the upper eyelid, the veins of the small Vf!IlOUS plexus drain into the ophthalmic vein, which drains posteriorly to the cavernous sinus. The veins in this region of the face do Chapter 1:Surgical Anatomy of the Head and Neck 5 2 :! 4 5 67 8 9 10 16 151413 12 11 A B Figura 1.2Eyelids andexternal adnexa. A:.1,Superior tarsus; 2,levator palpe- braesuparlorls muscle; 3,supraorbital artery andnerve; 4,supratrochlear artery and nerve; 5,lacrimal caruncle; 6,superior lacrimal papilla andpuncta; 7,bulbar conjunc· tlvaoversclera; 8,pupil; 9,cornea; 10,superior palpebral conJunctiva; 11,Inferior palpebral conjunctiva; 12,1nferlor lacrimal papilla andpuncta; 13,maxilla; 14,1acrimal sac;15,medial palpebral ligament; 16,Infraorbital foramen; 17,orbital septum; 18,Inferior tarsus; 19,orbicularis oculi musde (cut); 20,latQral palpebral ligament. B:1,Orbicularis oculi muscle; 2,orbital septum; 3,levator palpebrae superioris muscle; 4,superior tarsal musde (Muller muscle); 5,superior conjunctival fornix; 6,orbicularis oculimusde (palpebral portion); 7,superior tarsus; 8,tarsal glands; 9,palpebral conjuncliva; 10,inferior tarsus; 11,sclera; 12_choroid; 13,retina; 14,lens;15,iris;16,anterior chamber; 17,cornea. not have valves and may propagate septic emboli posteri- orly. This isaparticularly dangerous situation for patients who have infections in the areas of the eyelids or perior- bital absCf!lls. These patients are at risk of cavemow sinus thrombosis. Lacrimal System The lacrimal apparatus consists of asecretocy portion, the lacrimal gland, its ducts, the drainage apparatus, the lacrimal canaliculi and sac, and the nasolacrimal duct (F'tg. 1.3). The lacrimal gland ispartially divided into two portions by the lateral hom of the aponeurosis of the leva- tor palpebrae. The l;uger orbital portion of the gland lies in ashallow fossa on the frontal bone and is in contact ankriorly with the Oibital sepb.lm. The exaetocy ductules of the lacrimal gland run through the Oibital part of the gland, run through or dose to the posterior part of the pal- pebral portion, and are joined by ducts &om this portion. 2 ~r--"'r-+ 3 -1-~.,j- 4 ~-t-'TH-+ 5 6 7 8 Figure 1.3 Lacrimal appanrtus and drainage system. 1.Lacrimal gland and duct5; 2,superior lacrimal papma and puncta; 3,1acrimal car- unde; 4,lacrimal sac; 5,inferior lacrimal papilla and puncta; 6,middle nasal concha; 7,infaricr nasal concha; 8,opening ofnasolacrimal duct. 6 Sec:tion 1:Basic Science/General Medicine Figure 1.4 Bony orbit. Removal of the palpebral portion can destroy the drainage of the entire gland. Movement of the eyelid distributes tears aver the sur- face of the eye, and any excess tends to accumulate in the lacrimal lake. this structure drains into the paired superior and inferior canaliculi and from there into the lacrimal sac. The lacrimal sac ishoused in the bony lacrimal f088a of the medial o:rbital wall this drains into the nasal lacrimal duct and eventually into the inferior meatus of the nose. Orbit The bony o:rbit consists of the medial wall occupied largely by the ethmoid bone. lacrimal bone, and aportion of the nasal process of the maxilla (Fig. 1.4). The Boor of the o:rbit consists of the roof of the maxilla. The inferior orbital fissure isat its lateral er:tent. The zygomatic bone and greater wing of the sphenoid form the lateral orbital wall and join the frontal bone superiorly to complete the pyramidal bony orbit On its medial aspect are the paired ethmoidal foramina. which provide aroute to the o:rbit for the anterior and posterior ethmoidal arteries. The optic canal posteriorly transmits the optic ner:ve and ophthalmic artety. The superior orbital fissure transmits cranial nerves III. IV; V, and VI and provides an aperture for the ophthal- mic vein. Eye The eye consists of the cornea and sclera in the anterior aspect The anterior chamber protrudes as asecond sphere on the structure of the o:rbit. the lens and iris form the pos- terior portion of the anterior chamber. Contained within the substance of the eye isthe vitreous. The retina rests on the choroid. The fovea centtalis is the focal point of the eye. .Asymmetric to the structure of the o:rbit isthe insertion of the optic ner:ve and ciliaty arteries. the seven voluntary muscles of the o:rbit are the levator palpebrae superioris; the superiot inferiot medial, and lat- eral rectus muscles; and the superior and inferior oblique muscles (Fig. 1.5). The smooth muscles of the orbit are the orbitalis muscle, the superior and inferior tarsal muscles, and ciliary and iridial muscles within the eye. The superior oblique issupplied by cranial ner:ve IV; the lateral rectus Figure 1.5 Eye~ muscles. 1, Levator palpebrae~ superlorls muscle~; 2, supcarlor oblique~ musdca; 3,supcarlor rectus musdca; 4, optic nente; 5,lateral rectus musdca; 6,Inferior rectus muscle; 7, Inferior oblique muscle~; 8,mCidlal rectus musde; 9,trochlea; 10, annular tendon. iJ supplied by cranial neJVe Vl, and the other volWltary muscles of the o:rbit are supplied by cranial nerve DI. 1he tarsal and o:rbital muscles (of MUller) are supplied by sym- pathetic fibers derived from the carotid plexus and from the superior cemcal ganglion. The dilator pupillae, the sphincter pupillae, and the ciliary muscle are supplied by parasympathetic fibm through the oculomotor nerve (IU). The primary blood supply to the o:rbit is through the ophthalmic arteiy. The primary drainage is through the ophthalmic vein, which drains directly into the cavernous sinus. An additional anastomotic network iJpresent on the ankrior aspect of the face in the form of an arcade of ves- sels aroWld the eyelids and through the pterygoid plexus. THE EAR 1he development and the anatomic and physiologic fea- tures of the ear are diJcussed in Chaptf!rS 140 and 141. NOSE AND PARANASAL SINUSES External Nose The mcmal part of the nose isaroughly pyramidal shape. 1he skeleton of the extemal nose iJpartly bony and partly cartilaginous and membranous. 1he nasal bones, which are usually narrow and 1hicker above, wider and thinner below; articulate firmly above with the nasal part of the frontal bone and with each other laterally with the nasal process of the maxilla (Fig. 1.6). Attached to the inferior aspect of the nasal bones are the upper lateral cartilages. These are continuous wi1h 1he cartilaginous septum. In the inferior aspect. the lobule of the nose isformed mosdy by the lower lateral cartilages, which consist of amedial and Frontal bone rt-:H::?-- =:-t-H -Nasal bones Frontal process rr--T+t-+--F-:1-71'--W-- ofmaxilla Septalcartilage Lateral nasal cartilages Lesser alar ~-1+- cartilage Greater alar cartilage Lateral crus Medial crus Figure 1.6 Bony and cartilaginous anatomic configuration ofthe ext:lilrnal nose. Chapter 1: Surgical Anatomy of the Head and Neck 7 lateral crus. There are several small cartilages wi1hin the nasal ala. 1he chief arterial supply of the nose iJfrom the facial artery through the angular artery and superior labial arteries. Venous drainage iJ similar, with acomponent gaining access to the ophthalmic vein through draining vessels from the trochlear and angular veins. Nasal Cavity The nasal cavities are also known as the nasal fossoe. The nasal septum consists of the nasal septal cartilage, the nasal crest of the maxilla. the nasal crest of the palatine bone, 1he vomeJ;. and the perpendicular plate of the ethmoid bone. The lateral nasal wall isformed by the prominent nasal tur- binates. The meatus are situated below the corresponding tu:rbinates (Fig. 1.7). The inferior meatus provides drainage A Sphenoidbone B Figure 1.7 A:. Lateral nasal wall. 1. FRJntal 5inus; 2, middle nasal concha; 3, middle nasal meatu=r, 4,agger nasi; 5,atrium of midclle nasal a:mcha; 6, limen; 7, vestibule; 8, inferior nasal me- atus; 9, incisive canal; 10, palatine pl'OCII55 of mliDiilla; 11. 50ft palate; 12, pharyngeal AICIIW; 13, eustachian tiD orifiat; 14, toru5 tubarius; 15, adenoid; 16, sphenoid 5inu=r, 17, 5phenoid sinus opening; 18, sphenoethmoidal rec:e55; 19, inferior nasal ClDflc:ha; 20,5uperior nasal meatu5; 21, 5uperior nasal concha; 22, palatine bone. B:Nasal5eptum. 1,Perpendra~lar plate; 2,cribriform plat;: 3, aista galll; 4,frontal bone; 5,nasal bone; 6,septal cartilage; 7,rnedral aus; 8,anterior nasal spine; 9,Incisive canal; 10, palatine proo;ss; 11, pc~rpcmdrcular plate; 12, postnasal spine: 13, horizontal plate; 14, lateral pterygoid plate; 15, rnedral ptwygold plate; 16,sphenoid sinus; 17, aest:; 18, body. 8 Sec:tion 1:Basic Science/General Medicine for the nasolacrimal duct. The middle meatwl provides drainage for the anterior nasal sinuses, namely the frontal sinus, anterior ethmoid sinuses, and the maxillary sinus. The superior meatwl provides drainage for the posterior sinuses, namely the posterior ethmoid and sphenoid sinuses. The arterial supply of this region isfrom internal carotid sources tluough the anterior and posterior ethmoid arter- ies and from an external carotid source through the sphe- nopalatine artery. Contributions also may exist from the greater palatine vessels and the septal branch of the supe- rior labial artery. These form an important anastomotic network in the anterior septum lmown as the ICresselbach plexw, which accounts for most nosebleeds. Sinuses 1he paranasal sinuses consist of the paired frontal, eth- moid, maxillary, and sphenoid sinuses {Fig. 1.8). The fron- tal sinus develops as one of several outgrowtlul from the region of the frontal recess. Two, tluee, or even more fron- tal sinuses on aside have been reported, and some persons have no frontal sinus. The degree of pneumatization of the frontal sinuses varies. Pneumatization may extend into the roof of the o:rbit and laterally into the frontal bone as far as the sphenoid wing. The frontal sinuses drain into the anterior aspect of the middle meatus. Ethmoid Sinuses 1he ethmoid sinuses consist of avariable number of sepa- rate cavities that honeycomb the ethmoid bone between the upper part of the lateral nasal wall and the medial wall Figure 1.8 Paranasal sinuses. 1, Nasal MptUm; 2, frontal sinus; 3,nasal c:avltles; 4,rilmoldal calls; 5,middle nasal concha; 6,mldde nasal meatus; 7,maxillary sinus; 8,lnfQrlor nasal concha; 9,hard palatQ. of the o:rbit. The anterior ethmoid cells are divided into frontal recess cells, which open into the frontal recess of the middle meatus; infundibular cells, which open into the eth- moid infundibulum; and bullar or middle ethmoid cells, which open directly into the middle meatus on or above the ethmoid bulla There may be one to seven posterior ethmoid cells. The bullae and posterior ethmoid cells may encroach on each other and overlap, the bullar cells spread- ing backward or the posterior cells spreading forward. The posterior ethmoid cells drain into the superior meatus. Sphenoid Sinus 1he sphenoid sinus usually opens into the sphenoeth- moidal recess above and behind the superior nasal concha. The ostium usually is in the posterior wall of the recess, but sometimes itison its lateral wall. The degree of pneu- matization of the sphenoid sinus varies. This variation is an important factor in surgical approaches to the pituitary gland. The relations of the sphenoid sinus are important because of the surrounding anatomic structures. The optic nerves are superior to the sinus, and the internal carotid artery is lateral to the sinus within the c:avemous sinus. 1he maxillary nerve lies in the inferior lateral portion of the sinus in the anterior aspect. The hypophysis lies within the posterior superior portion of the sphenoid sinus and can be approached through transsphenoidal hypophysectomy. Maxillary Sinus 1he maxillary sinus usually is the largest of the paranasal sinuses and issituated in the body of the maxilla. Its ante- rior wall isthe facial surface of this bone. and its posterior wall isthe infratemporal surface. Its medial wall isthat of the nasal cavity. The roof of the maxillary sinus isalso the floor of the orbit. and italso may be aH'ected in blow-out fracture8 of 1he o:rbit. The maxillary sinus drains into the middle meatus of the nasal cavity. The roots of the poste- rior molar teeth may extend into the sinus. The maxillary sinus isbounded posteriorly by the pterygomaxillary fossa, tluough which course the terminal branches of the internal maxillary artery. These vessels can be approached tluough the maxillary sinus for relief of epistaxis. THE FACE Facial Bones and Muscles The bones of the face include 1he frontal and nasal bones and the facial bones proper-maxilla. mandible, zygo- matic, and palatine bones. The facial and mimetic mus- cles are divided into five chief groups concerned with the mouth, nose, orbit. ear, and scalp (Fig. 1.9). The platy!ma muscle in the neck also belongs to the facial group. The chief action of these muscles ison skin into which they insert. All these muscles are innervated by the facial nerve Figure 1.9 Fadal muscles. 1,Galea aponeurotica; 4frontalis; 3, procerus; 4, depressor supercllll; 5, corrugator superdlll; 6, orbicularis OC1JII; 7, nasalis; 8, levator labll superlorls; 9, levator anguli oris; 10, levator labli superioris alaeque nasi; 11, orbicularis oris; 12, mentalis; 13, depressor labll inferi· oris; 14, depr'Qssor anguli oris; 15, platysma; 16, masseter; 17, zygomaticus major; 18, zygomaticus minor; 19, temporalls; 20, 1ateral pterygoid; 21, medial pterygoid; 24 buccinator. Parotid Gland The parotid gland, which isanterior to and below the lower part of the eru;. extends subcutaneously backward over the anterior portion of the sternocleidomastoid muscle, Figure 1.10 Parotid gland and facial nerve. 1,Temporal branch; 4zygomatic branch; 3,buccal branch; 4,masseter muscle; 5,mal'- ginal mandibular branch; 6, arrterior digastric muscle; 7, a~rvlcal branch; 8,parotid gland; 9,posterior digastric musde; 10, seventh cranial orfadal nerve; 11, pes anSQrinus. forward over the masseter muscle, and deeply behind the ramus of the mandible to lie bet:wem the mandible and the ex:tfmal acoustic meatus and mastoid process (Fig. 1.10). The gland isroughly divided into alateral and medial portion by the course of the facial nerve. Related to the parotid gland are several perlparotid and intraparotid lymph nodes, which may swell. The parotid gland drains through the parotid duct. Itis innervated by the auriculo- temporal ne:rve from the otic ganglion. Facial Nerve The anatomic characteristia of the facial ne:rve vary in the extracranial portion of the nerve. Identification of the nerve depends on marking the position of the posterior belly of the digastric muscle, the mcmal meatal cartilage, the tym- panomastoid suture line, and the styloid process. ORAL STRUC1URES Maxilla The maxilla is the chief component of the upper jaw (Fig. 1.11 ).In addition to housing the dental apparatwl and the maxillary sinus, itisrelated posteriorly to the medial and lateral pterygoid plates. The hard palate unites the paired maxilla and forms the bony roof of the oral cavity. Sensation to the upper teeth isprovided by the max:ilhuy nerve through the posterior superior and anterior superior alveolar nerws. The in&ao:rbital nerve, another branch ofV2, provides sensa- tion over the face of the maxilla and soft tissues. Chapter 1: Surgical Anatomy of the Head and Neck 9 10 Sec:tion 1:Basic Science/General Medicine A B 10 / Figure 1.11 Maxilla andjaw.A:f,Sphenopalatine artery; 2.posterior lateral nasal artery; 3,pomrior septal arteries; 4,anastomosis intheinci- sivecanal; 5,greater palatine artery; 6,lesser palatine artery; 7,de5CIInding palatine artery; 8,superior alveolar arteries; 9,artery ofthepterygoid canal; 10,anterior andpomrior deep temporal arteries; 11,accessory meningeal artery; 12,middle meningeal artery; 13,anterior tympanic artery; 14,deep auricular artery; 15,auriculotemporal nerve; 16,superiicial temporal artery; 17,buccal artery; 18,masseteric artery; 19,inferior alveolar artery; 20,ascending pharyngeal artery; 21,asamdlng palatinaartary; 22,tonsillar ar- t«y;23,CIX't:Cirnal carotid artery; 24,fac:lalartary; 25,suptarlor constrictor muscle. 1:D,Digastric musda (cut}; M,mylohyoid artery andnarva; lA.Inferior alv&Oiar artery andnarvta; LA.lingual artery; L.lingual narva; MPT, mCidlal pterygoid muscle~ andartary; A.angular artery; sr.supratrochlear artery; 50,supraorbital artery; f.PT,latCiral pterygoid muscle~; Sl.,sphenomandibular ligament; 0,ophthalmic artery. Palate The palate intervenes between 1he rwal and oral cavities (Fig. 1.12). Itconsists of the maxilla. the horizontal pro- cess of 1he palatine bone. and 1he pterygoid plates. Soft tis- sues covering 1his area form the hard and soft palates ofthe roof of the mouth. The skeletal core of the soft palate iathe palatine aponeurosia. The most superficial muscle fibers on 1he pharyngeal surface of 1he soft palate are those of 1he palatopharyngeus muscle. The levator veli palatinl tensor veli palatinL and uwlar muscle complete the strucwres of the soft palate. Mandible The mandible, or lower jaw, consists of the tooth-bearing body and the ramus that extends upward from the angle of the mandible. The ramus, including the angle, is cov- ered externally by the masseter muscle, which isCI'OSSed by the facial nerve and parotid duct Between the ramus and the medial pterygoid muscle are the inferior alveolar and lingual nerves. Overlapping the posterior border of the ramus isthe parotid gland, and within and parallel- ing this border is1he upper portion of 1he external carotid artery. The superficial branch of this artery ema:ges from Chapter 1: Surgical Anatomy of the Head and Neck 11 ...:.....--t-14 ll-H....----"<---- -'--+13 ----t-12 -+--i-11 Figure 1.12 Palate. 1,Velipalati mu5cle5; 2,greater palatine foramina; 3,le55er palatine foramina; 4,ptery- goidhamulus; 5,superior pharyngeal conJtrictor muscle; 6,pterygoman- dibular raphe; 7,buccinator muscle; 8,palatopharyngeus musde; 9,pala- toglo55u5 musde; 10,uvula; 11,pala- tinetonsil; 12,palatopharyngeal arch; 13,uvular muscle; 14,palatoglossal arch; 15,palatine~ glands; 16,greater pala1ina art8ry andnerve; 17,lesser pala1ina art8ry andI'Kirw; 18,salpln· gopharyngeus musde; 19,levator wllpalatlni muscle; 20,tensor vel! pala1i musde; 21,pharyngobasllar fasda; 22,cartilaginous auditory tube; 23,carotid canal; 24,vallate papillae; 25,inds!VCI forar!'Kin. the parotid gland behind the temporomandibular joint and its internal maxillary branch runs transversely deep to the ramus. Inferiorly and medially, the angle and posterior part of the body of the mandible are related to the sub- mandibular gland, and medially, the anterior part of the mandible is adjacent to the sublingual glands. The mus- OJlature most intimately concerned with the mandible and its movements consists of the masseter, temporal, and two pterygoid muscles (Fig. 1.9). 1hese muscles govern Digastric m. :....__--lr -anterior belly Digastric m. posterior belly maatication and are innervated by the third division of the trigeminal nerve. Hyoid Bone and Tongue lhe hyoid bone, to which are attached infrahyoid and suprahyoid muscles, effectively separates the ante- rior suprahyoid and infrahyoid fascial compartments. lhe suprahyoid muscles are the digastric and stylohyoid Figure1.13 Suprahyoid musdCIS. 12 Sec:tion 1:Basic Science/General Medicine muscles, the mylohyoid and the geniohyoid muscles, and the muscles of the tongue (Fig. 1.13 ).The extrimic muscles of the tongue are the genioglossus, the hyoglossus, and the styloglossus. The intrinsic muscles of the tongue are com- plicated bundles of interlacing fibers, among which are connective ti8sue septa. The midline septum lies be~en and effectively separates the muscles, nerves, and vessels of the two sides. Itisan almost bloodless midline plane. Submandibular Gland The submandibular gland occupies most of the subman- dibular triangle and expands beyond this area over the superficial structures of the anterior and posterior bellies of the digastric muscle (Fig. 1.14). Its posterior border is close to the lower part of the parotid gland at the angle of the jaw, where itisseparated from this gland by the stylo- mandibular ligament The submandibular gland iscrossed superficially by the facial vein and sometimes by the ramus mandibularis branch of the facial nerve The largu sub- mandibular lymph nodes lie along the superficial upper border of the gland, between it and the mandible. The ankrior portion of the submandibular gland lies directly against the mylohyoid muscle and the mylohyoid nerve. Medial to the mandible and above the level of the sub- mandibular gland isthe lingual nerve in its course toward the tongue. When the submandibular gland is removed, Figure 1.14 Submandibular viangle. 1, Palatoglossus musde; 2, lingual nerve; 3, superior constrictor muscle; 4, styloglossus musde; 5, stylopharyngeus muscle; 6, hyoglossus musde (cut); 7,stylohyoid musde (cut); 8, external carotid artery; 9, internal jugular vein; 10, hypoglossal nerve; 11, digastric muscle, anterior belly; 12, geniohyoid muscle; 13, genioglossus muscle; 14, sub- lingual artery and vein; 15, submandibular duct; 16, deep lingual artery and vein; 17, 5Ubmandibular ganglion; 18, deep lingual artery; 19, common facial win; 20, hyoid bone. the facial vein is saaificed, but the ramus mandibularis branch of the facial nerve ispreserved to avoid disruption of the comer of the mouth. The facial artery passes across the upper surface of the gland, usually grooving itdeeply before rounding the lower border of the mandible, and must be sacrificed in removal of the gland. The subman- dibular and sublingual glands are innervated from the sub- maxillary ganglion fibers that accompany the sensory fibers of the lingual nerve. These fibers originate in the chorda tympani and pass into the submandibular ganglion. PHARYNX AND LARYNX 1he wall of the phacynx consists of mucosa and voluntary muscle. The mucosal structure of the pharynx varies. That of the nasal part isciliated and resembles the mucosa of the nose. In the rest of the pharynx. the epithelium isstratified Figure 1.15 Pharynx.. 1, Digastric musde, posterior belly; 2,adenoid; 3,pharyngeal raphe; 4,pharyngobasilar fa5Cia; 5,sty- lopharyngeus muscle; 6,longitudinal esophageal muscle; 7,circu- lar esophageal muscle; 8,posterior cricoarytenoid musde; 9,cri- <X1pharyngeus muscle; 10, vansverse and oblique interaryt:enoid musde; 11, inferior <XInstrictor musde; 12, hyoid bone; 13, mid- dle <XInstrictor muscle; 14, palatopharyngeus musde; 15, uvula; 16, superior <XInstrictor muscle; 17, levator veli palati musde; 18, cartilaginous auditory tube. Please note that the posterior belly ofthe dlgasvlc musde arises from the mastoid notch on the medial side ofthe base ofthe mastoid proo;ss. squamous tissue. The musrularwall of the pharynx with its thin covering ofbuccal pharyngeal orvisceral fascia issepa- rated from the prevertebral fascia by an area of loose con- nective tissue that constitutes the retropharyngeal space. Nasopharynx The nasal part of the pharynx,. the nasopharynx, iscontinu- ous anteriorly through the choanae with the nasal cavities (Fig. 1.15). The floor is the upper surface of the soft pal- ate. The fornix or roof, the mucosa of which is attached dose to the base of the skull, slopes downward and back- ward to become continuous with the posterior wall. The eustachian tubes are prominent on the lateral aspect of the nasal pharynx. There may be adenoid tissue in the superior recess of the nasopharynx. Oropharynx The oropharynx iscontinuous anteriorly through the fauces, or oral pharyngeal isthmus, with the oral cavity. The bound- aries of the fauces are the posterior border of the soft palate above, the palatine arches laterally, and the dorsum of the tongue. Below the fauces, the anterior wall of the pharynx is the posterior or pharyngeal dorsum of the tongue. On the posterior parts of the dorsum of the tongue lie irregu- lar nodules of tissue known as the lingual tonsils. The lat- eral wall of the passageway of the fauces houses the large palatine tonsils. The lingual tonsils in the anterior aspect, the palatine tonsils inthe lateral aspect,. and the pharyngeal tonsils or adenoids in the posterior and superior aspects form aring of lymphoid tissue known as the Waldeyer ring. Hypopharynx The laryngeal part of the pharynx,. or hypopharynx, extends from just above the level of the hyoid bone superiorly to the lower border of the cricoid cartilage inferiorly, narrow- ing rapidly to become continuous with the esophagus. The anterior wall isformed laterally by mucosa on the medial surface of the thyroid cartilage and centrally or medially by the larynx and its appendages. Above are the epiglottis and the aditus of the larynx. Below the aditus, the anterior wall of the pharynx isalso the posterior wall of the larynx. Lateral to the epiglottis are the lateral glossoepiglottic folds that form the anterolateral boundary between the oral and laryngeal parts of the pharynx. Below these folds, the hypo- pharynx extends forward around the sides of the larynx between this area and the thyroid cartilage. These bilateral expansions are the piriform recesses or sinuses. The intrinsic portion of the larynx consists of the epi- glottis, false vocal folds, laryngeal ventricles, paired true vocal folds, and arytenoid cartilages in the posterior aspect Contained within the aryepiglottic folds are the paired cor- nirulate and cuneiform cartilages. The space between the two vocal folds isthe glottis. Chapter 1: Surgical Anatomy ofthe Head and Neck 13 The muscles of the pharynx are the superior, middle. and inferior constrictors. These muscles look like ice cream cones inserted into one another. They gradually merge to form the cricopharyngeus muscle at its inferior extent and then the esophagus. Each constrictor inserts with the corre- sponding muscle of the opposite side and the midline into aposterior midline raphe. These muscles are innervated by cranial nerve Xthrough the pharyngeal plexus. Dehiscence in the pharyngeal constrictors may give rise to zenker diverticula. Immediately lateral to the pharyngeal muscles are the great vessels of the neck and cranial nerve X. Larynx The major structural elements of the larynx are the shield- shaped thyroid cartilage and cricoid cartilages (Fig. 1.16). They join through the cricothyroid joint. The superior cornua of the thyroid ala artirulate through several small cartilages with the hyoid bone. Overlying the structure of this skeletal framework are the infrahyoid muscles, which include the paired sternohyoid, sternothyroid, omohyoid, and thyrohyoid muscles. The epiglottis isformed of fibroelastic cartilage and has multiple perforations that allow free access of lymphatic drainage or tumor to the preepiglottic space. The preepi- glottic space is aC-shaped space bounded superiorly by the median glossoepiglottic ligament, inferiorly by the thy- roid cartilage. anteriorly by the thyrohyoid membrane, and posterolaterally by the epiglottis and aryepiglottic folds. Free dissemination of tumor can occur within the preep- iglottic space. The paired arytenoid cartilages provide an attachment for the vocal ligament and movement of the vocal folds. The intrinsic muscles of the larynx are inner- vated by the recurrent laryngeal nerve. The exception isthe cricothyroid muscle, which is innervated by the superior laryngeal nerve. The recurrent laryngeal nerve enters infe- riorly and laterally to the cricothyroid articulation through the Killian-Jamieson area. The recurrent laryngeal nerve on the left originates over the aortic arch and ascends in the neck to innervate the larynx. On the right this structure goes around the subclavian artery. THE NECK Cervical Triangles The prominent landmarks of the neck are the hyoid bone. the thyroid cartilage. the trachea, and the sternocleidomas- toid muscles (Fig. 1.17). The sternocleidomastoid muscles divide each side of the neck into two major triangles, ante- rior and posterior. The anterior triangle of the neck may be further delimited by the strap muscles into the superior and inferior carotid triangles. The posterior triangles or lat- eral triangles ofthe neck are formed by the posterior border of the sternocleidomastoid muscle anteriorly, the clavicle inferiorly, and the anterior border of the trapezius muscle 14 Sec:tion 1:Basic Science/General Medicine Epiglottis I,, Corniculate cartilage (( }Inter- \1 arytenoid m Thyroarytenoid m. Posteriorcricoarytenoid m. Lateralcricoarytenoid m. Cricothyroid m. Transverse & oblique arytenoid m.PosteriorCricoarytenoid m. Cricoidcartilage Foramen for Internallaryngeal n.and sup.laryngealvessels Epiglottis Thyroepiglottic lig.;-.:..:..:~.-::::_~R.\ Vocalligaments Hypoepiglott!cligamentThyroidcartilage Figure 1.16 Larynx. Digastric m post. belly Sternocleido-mastoid m. (cut) Thyrohyoid m. Figure 1.17 Musdes and 1riangles of the neck. S,scalene mu&- de; M, masseter. posteriorly. 1he omohyoid muscle divides this triangle of the neck into asmall inferior subclavian triangle and alarger posterior occipital mangle Deep to these muscles are the scalenes, which form much of the muscle mass of the posterior and lateral portions of the neck. 1he bachial plexus and subclavian artery course between the anterior and middle scalene muscles. The subclavian vein courses anteriorly to the anterior scalene muscle. Inferior Portion of the Neck In the inferior root of the neck and closely associated with the brachial plexus are the paired phrenic nerves that course medially to innervate the diaphragm (Fig. 1.18). These nf!l'Vl!8 originate in the ventral rami of the cervical plexus of the thin:l, fourth, and fifth cemcal nerve rootlets. The subclavian artery gives rise to the thyrocervical trunk The transverse cemcal and suprascapular arteries usu- ally course laterally aver the surface of the phrenic nerve This relation allows identification of these structures. The vagus nerve lies further medially and iscontained within the carotid sheath. Itshares the sheath with the common, internal. and external carotid arteries and jugular vein. Posterior to the carotid sheath lies the cervical sympathetic nerve. On the surface of the carotid sheath lie the ansa hypoglossi nerves. 16 Figure1.18Rootofneck.1,Stylohyoidmuscle;2,hypoglos· salnerve(c:nnlalnerveXII);3,digastricmuscle;4,parotidgland; 5,sternodeidomiStoid muscle; 6, greater auricular nerw; 7,lesseroccipitalnerve;8,ventralramus(C2);9,ventralramus (Cl);10,aca~ssorynerve(cranialnerveXI);11,ventralramus (CS);12,anteriorscalenemusde;13,phrenicnerve;14,brachial plexus;15,subdavlanarteryandvein;16,thyrocervicaltrunk; 17,vagusnerve;18,Inferiorrootansacervlcalls;19,superiorroot aruaarvicalis;20,superiorthyroidartery. LateralPortionoftheNeck 1hedominantstructureofthelateralcervicaltriangleisthe spinalaccessorynerveItemanatesfrom theposteriorbor- derofthesternocleidomastoidmuscleindoseassociation withthesplayofneiVeSofthecervicalsensoryplexus.It inneiVatesthetrapeziusmuscleonitsinferioraspectinclose associationwiththetranneuecervicalarteryorsuprascapu- lararte:Jy,whichvariablysuppliesthetrapeziusmuscle. ArterialSupply 1hetwocommonOU'Otidarteriesdifferinlengthbecausethe rightcarotidU8Uallyari.safrom thebrach.yt:ephalicartery behindthestemoclavirularjointandtheleftariseafrom the archoftheaorta(Fig.1.19).Botharteriesendbybifun:at- ingintotheint.emalandexternalcarotidarteries.Overthe latemlaspectoftheseartcrie8coursethepairedhypoglossal neiVe~J.Theinternalcarotidarteiyissituatedmoreposte- riorlyandhasnobranches.Theexternalcarotidarteiyhas branchesandliesslightlyanteriorly.ThisinfoiiDationcanbe Chapter1:SurgicalAnatomyoftheHeadandNeck 15 Figunt1.19Arterialsupplyoftheneck.1,Commoncarotid artery;2,superiorlaryngealartery;3,superiorthyroidartery; 4,internalcarotidartery;5,externalcarotidartery;6,lingualartery; 7,occipitalartery;8,ascending pharyngealartery;9,int. rioralwolarartery;10,maxillaryartery;11,ascendingpalatine artery;f2,fadalartery;13,mentalartery;14,submentalartery; 15,angularartery;16,infraorbitalartery;17,buo::alartery;18,sphe- nopalatineartery;19,middlemeningealartery;20,superfidaltem- poralartery. crucialind.iffm:ntiatingthetwovessdsforligation.Fromits origin.theintemalcarotidarteryascendsdirectlytowardthe carotidcanalandiscrossedlaterally.inascendingo ~ by thehypoglossalIlCIW,.occipitalarte:Jy,posteriorbellyofthe digastricandassociatedstylohyoidmuscle,andtheposte- riorawicularartery.Stillhigherandclosetothebaseofthe skulLthememalcarotidarteryisanterolatelaltotheinter- nalcarotidartcJy,andthestylopharyngeusmuscleandasso- ciatedglossoplwyngealn ~ thephacyngealbranchofthe wgus,andthestylohyoidligamentallpasslate:Jallytothe internalcarotid.b ~ itandtheemmalcarotidartery. Afteritsorigininthecarotidtriangle,theexternalcarotid arterypassesupw.ud,deeptotheposteriorbellyofthe digastricandstylohyoidmuscles,andcrossesthestyloglos- susandthestylopharyngeusmusclesontheirlatemlaspects; then,paralldtotheramusofthemandible,itpasseainto thedeeperportionoftheparotidgland.1heexternalcarotid arteryhubranchestothesuperiorthyroid.lingual,fadal, ascendingphmyngeal,occipital,posteriorauricular,maxil- lary,transversef.acial,andsuperficialtemporalarteries. 16 Sec:tion 1:Basic Science/General Medicine Venous Supply 1he veins of the neck vary considerably in their connec- tions with each other and in their relative sizes (Fig. 1.20). Those conducting blood downward from the head and face include the external jugular, anterior jugulat internal jugulat and vertebral veins. At the base of the neck are the suprascapular and transverse cervical veins and the subcla- vian vein. which unites with the internal jugular vein to form the brachycephalic or innominate vein. 1he subcuta- neous veins and the external and anterior jugular veins are especially variable in size and course Figure 1.20 Venous supply of the! neck. 1, Subclavian win; 2,Internal Jugular vein; 3,anterior external Jugular vein; 4, supe· rlor laryngeal vein; 5,superior 1hyrold vein; 6,common facial win; 7, posterior external jugular vein; B, rQtromandlbular win, ante· rlor division; 9,ret:romandlbular vein, posterior division; 10, Inferior alveolar vein; 11, posterior auricular vein; 12, superficial temporal vein; 13, deep temporal vein; 14, pterygoid plexus; 15, deep facial vein; 16,lnfraorbltal win; 17, angular vein; 18, mental win; 19, facial vain; 20, external paiBtine vain. Lymphatic Vessels 1he lymphatic system of the neck consists of numerous lymph nodes intimately connected with each other by lymphatic channels and the terminations of the thoracic and right lymphatic ducts. 1he deep cervical lymph nodes are numerous and prominent. and many of them are large They form achain embedded in the connective tissue of the carotid sheath. Most are in that portion of the sheath around the internal jugular vein. 1hey extend from the base of the skull to the base of the neck. Two nodes that dese:m! partia:ilar attention are the superior jugulodigastric node at the junction of the internal jugular vein and the posterior belly of the digastric and the inferior juguloomo- hyoid node at the junction of that muscle and the internal jugular vein. Block resection of the neck in astandard radi- cal or modified manner relies on reproducible and consis- tent lymphatic drainage pathways for success. Viscera The visceral struelllres of the neck include the thyroid and parathyroid glands, aportion of the pharynx, the laJ)'l'lX. the trachea. the esophagus, and sometimes portions of the thymus (Fig. 1.21 ).The thyroid gland lies below and on the side of the thyroid cartilage, cavued anteriorly by the infrahyoid muscles. Apyramidal lobe of the thyroid may extend superiorly from the isthmus that connects the two lobes of the thyroid gland. On the posterior surface of the thyroid gland lie the paired parathyroid glands. Successful parathyroid exploration and thyroidectomy depend on accurate identification and preservation of the recurrent laryngeal neiVes and identification of the parathyroid glands. Landmarb that are used successfully tolocate these Internaljugular v.- --fi Right lobe thyroid gland Middle thyroid v. Inferior thyrofd a. Thyrocervicaltrunk Subclaviana.&v. Figure 1.21 Thyroid and parathyroid glands. structures include the trachea,. common carotid artery, and inferior thyroid artery, which form atriangle within which the surgeon usually finds the recurrent laryngeal nerve. Lymphatic drainage occurs along the peritracheal nodes. Venous drainage similarly is directed inferiorly along the inferior thyroid veins. The four or more parathyroid glands develop from the dorsal extremities of the third and fourth pharyngeal pouches. As the thyroid and thymus and their associated parathyroid glands move caudally from the region inwhich they originate. the thymus normally descends beyond the level at which the thyroid halts. The parathyroids from the fourth pouches (superior parathyroid glands) usually are situated more craniad than the thyroid gland, and those derived from the third pouches (inferior parathyroid glands) are usually freed from the thymus and become Chapter 1: Surgical Anatomy of the Head and Neck 17 associated with the thyroid gland at its lower pole. Both sets of parathyroid glands usually are situated on the pos- terior aspect of the lateral lobes of the thyroid gland, but there are many exceptions. Because ofthe manner inwhich they arise and migrate into the neck, the glands often are displaced and may be situated in other portions of the thy- roid gland or lie above or below it. BIBLIOGRAPHY Hollinshead, WH. Anatomy for surgeons: the head and neck, 2nd ed. Hagerstown, MD: Harper&. Row, 1968. Netter, FH. Atlas ofhuman anatomy. Summit, NJ: Ciba-Gcigy, 1989 . Pemkop£; E.Atlas oftopographical and applied human anatomy: head and neck. Philadelphia, PA: WB Saunders, 1963 . Williams, PL, Warwick, R, Dyson, M, eds. Gray's anatomy, 37th ed. Edinburgh. UK: Churchill Livingstone 1989 .