Chapter 53: THE PHARYNX AND LARYNX (2025)

Pharynx

The word throat is used for the parts of the neck anterior to thevertebral column, especially the pharynx and the larynx. Thepharynx is the part of the digestive system situated posterior to thenasaland oral cavities and posterior to the larynx. It is thereforedivisible intonasal, oral, and laryngeal parts: the (1) nasopharynx, (2) oropharynx,and (3) laryngopharynx. The pharynx extends from the base of the skulldown to the inferior border of the cricoid cartilage (around the C6vertebral level), where itbecomes continuous with the esophagus. Its superior aspect isrelated to thesphenoid and occipital bones and the posterior aspect to theprevertebral fascia andmuscles as well as the upper six cervical vertebrae. The pharynx (figs.53-1, 53-2, 53-3 and 53-4) is afibromuscular tube lined by mucous membrane.

The pharynx is the common channel for deglutition (swallowing) andrespiration, and the food and air pathways cross each other in thepharynx. In the anesthetized patient, the passage of air through thepharynx is facilitated by extension of the neck.

Subdivisions

Nasopharynx.

The nasopharynx, at least in its anterior part, may be regardedas the posterior portion of the nasal cavity, with which it has acommon function as part of the respiratory system. The nasopharynxcommunicates with theoropharynx through the pharyngeal isthmus, which is bounded by the softpalate, the palatopharyngeal arches, and the posterior wall of thepharynx. The isthmus is closed by muscular action duringswallowing. The choanae are the junction between nasopharynx and thenasalcavity proper.

A mass of lymphoid tissue, the (naso)pharyngeal tonsil is embedded inthe mucous membrane of the posterior wall of the nasopharynx. Enlarged(naso)pharyngeal tonsils are termed "adenoids" and may causerespiratory obstruction. Higher up, a minute pharyngeal hypophysis(resembling the adenohypophysis) may be found (see fig. 53-5).

Each lateral wall of the nasopharynx has the pharyngealopening of the auditory tube, located about 1 to 1.5 cm (1) inferior totheroof of the pharynx, (2) anterior to the posterior wall of the pharynx,(3) superior to the level of the palate, and (4) posterior to theinferior nasalconcha and the nasal septum (fig. 53-5). Theauditory tube can be catheterized through a nostril. The opening islimited on the superior side by a tubal elevation (tubal torus), fromwhich mucosal folds descend tothe palate and side wall of the pharynx. The part of thepharyngeal cavity posterior to the tubal elevation is termed thepharyngealrecess. Nearby lymphoid tissue is referred to as the tubal tonsil.

The auditory tube is pharyngotympanic; i.e., it connects thenasopharynx to the tympanic cavity. Hence, infections may spread alongthis route. The tube equalizes the pressure of the external air andthat in the tympanic cavity. The auditory tube, about 3 to 4 cm inlength, extends posteriorly, laterally, and superiorly. It consists of(1) acartilaginous part, the anteromedial two thirds, which is adiverticulum of the pharynx, and (2) an osseous part, theposterolateral third, which is an anteromedial prolongation of thetympaniccavity. The cartilaginous part lies on the inferior aspect of theskull, in a groove between the greater wing of the sphenoid bone andthe petrous part of the temporal bone (see fig. 42-12). Thecartilaginous part of the auditory tube remains closed except onswallowing or yawning, when its opening prevents excessive pressure inthe middle ear. The osseous part of the tube is within the petrouspart of the temporal bone.

Oropharynx.

The oropharynx extends inferiorward from the soft palate to thesuperior border of the epiglottis. It communicates anteriorly withthe oral cavity by the faucial (oropharyngeal) isthmus, which isbounded superiorly by the soft palate, laterally by the palatoglossalarches, and inferiorly by the tongue (see fig. 53-1). Thisarea is characterized by a lymphatic ring composed of thenasopharyngeal, tubal, palatine, and lingual tonsils.

The mucous membrane of the epiglottis is reflected onto the base of thetongue and onto the lateral wall of the pharynx. The space on eachside of the median glosso-epiglottic fold is termed the epiglotticvallecula.

Each lateral wall of the oropharynx has the divergingpalatoglossal and palatopharyngeal arches, which are produced by thesimilarly named muscles and are often called the anterior and posteriorpillars of the fauces, respectively. The triangular recess (tonsillarfossa) between the two arches lodges the palatine tonsil, which isoften referred to as merely "the tonsil" (see fig. 53-1). (Atonsil is a mass of lympoid tissue containing reaction or germinalcenters and related to an epithelial surface in the pharynx.) Themedial surface of the tonsil usually has an intratonsillar cleft(commonly but inaccurately called the "supratonsillar fossa") and anumber of crypts (fig. 53-6). The lateral surface is covered by a fibrouscapsule and is related to fascia, the paratonsillar vein (the chiefsource of hemorrhage after tonsillectomy), and pharyngeal musculature.The tonsil is supplied by the tonsillar branch of the facial artery,and it drains into the facial vein. Involution of the tonsil begins atpuberty.

Laryngopharynx.

The laryngopharynx extends from the superior border of theepiglottis to the inferior border of the cricoid cartilage, where itbecomes continuous with the esophagus. Its anterior aspect has theinlet of the larynx and the posterior aspects of the arytenoid andcricoidcartilages. The piriform recess, in which foreign bodies may becomelodged, is the part of the cavity of the laryngopharynx situated oneach side of the inlet of the larynx (see fig. 53-3).

Muscles

The pharynx consists of four coats of muscles, from within outward: (1)amucous membrane continuous with that of the auditory tubes and thenasal, oral, and laryngeal cavities; (2) a fibrous coat, that isthickest in its superior extent(pharyngobasilar fascia) and that forms a median raphe posteriorly; (3)amuscular coat, described below; and (4) a fascial coat (buccopharyngealfascia) covering the outer surface of the muscles.

The wall of the pharynx is composed mainly of two layers of skeletalmuscles. The external, circular layer comprises three constrictors(fig. 53-7and table 53-1). The internal, chiefly longitudinal layerconsists of two levators: the stylopharyngeus and the palatopharyngeus.

The constrictors of the pharynx have their fixed points in theanterior larynx,where they are attached to bones or cartilages, whereas they expandposteriorly, overlap one another from inferior to superior, and end ina mediantendinous raphe in the posterior midline. Their overlapping hasbeen comparedwith that of three flower pots placed one inside another. The inferiorconstrictor arises from the cricoid and thyroid cartilages. Thecricopharyngeal fibers are horizontal in orientation and continuouswith the circularfibers of the esophagus. These fibers act as a sphincter and preventair fromentering the esophagus. A pharyngeal diverticulum may formposterior to the larynx through the fibers of the inferior constrictor.Themiddle constrictor arises from the hyoid bone, whereas the superiorconstrictor arises from the mandible and sphenoid bone. * The constrictor muscles are insertedinto themedian raphe posteriorly.

The palatopharyngeus muscle arises from the palate, forms thepalatopharyngealfold, and is inserted into the thyroid cartilage and the side of thepharynx. The stylopharyngeus muscle arises from the styloid process,passesbetween the superior and middle constrictors, and is inserted with thepalatopharyngeus. The stylopharyngeus is supplied by theglossopharyngeal nerve, whereas the palatopharyngeus and theconstrictor muscles are innervated by the pharyngeal branch of thevagus nerve(probably fibers from the accessory nerve) through the pharyngealplexus that is located on the middle constrictor.

The chief action in which the muscles of the pharynx combine isdeglutition (or swallowing), a complicated, neuromuscular act wherebyfood is transferred from (1) the mouth through (2) the pharynx and (3)the esophagus to the stomach. The pharyngeal stage is the mostrapid and most complex phase of deglutition. During swallowing, thenasopharynx and vestibule of the larynx are sealed but the epiglottisadopts a variable position. Food is usually deviated laterally by theepiglottis and ary-epiglottic folds into the piriform recesses of thelaryngopharynx, lateral to the larynx. The pharyngeal ridge is anelevation or bar on theposterior wall of the pharynx inferior to the level of the soft palate;it isproduced during swallowing by transverse muscle fibers.

Innervation and bloodsupply

The motor and most of the sensory supply to the pharynx is by wayof the pharyngeal plexus, which, situated chiefly on the middleconstrictor, is formed by the pharyngeal branches of the vagus andglossopharyngeal nerves and also by sympathetic nerve fibers. The motorfibers in the plexus are carried bythe vagus (although they likely represent cranial accessory nerve components) and supply all the muscles of the pharynx and softpalate except the stylopharyngeus (supplied by cranial nerve IX) andtensor veli palatini (supplied by cranial nerve V). The sensory fibersin the plexus are from the glossopharyngeal nerve, and they supply thegreater portion of all three parts of the pharynx. The pharynx issupplied by branches of the external carotid (ascending pharyngeal) andsubclavian (inferior thyroid) arteries.

Larynx

The larynx is the organ that connects the lower part of the pharynxwith the trachea. It serves (1) as a valve to guard the airpassages, especially during swallowing, (2) for the maintenance of apatent airway, and (3) for vocalization.

The anterior aspect of the larynx is quite superficial (fig. 53-8) andthe posterior aspect of the larynx is related to thelaryngopharynx, the prevertebral fascia and muscles, and to the bodiesofcervical vertebrae 3 to 6. Laterally, the larynx is related to thecarotid sheath, infrahyoid muscles, sternomastoid muscle, and thethyroid gland.The larynx is elevated (particularly by the palatopharyngeus muscle)duringextension of the head and during deglutition.

The larynx can be examined in vivo by means of a mirror (indirectlaryngoscopy) or a fiber optic instrument (direct laryngoscopy)(seefigs. 53-11Cand D and 53-12).

Cartilages (figs. 53-8, 53-9, 53-10 and 53-14)

The larynx possesses three single cartilages (thyroid, cricoid, andepiglottic) and three paired cartilages (arytenoid, corniculate, andcuneiform). The thyroid, cricoid, and arytenoid cartilages are composedof hyaline cartilage and may undergo calcification, endochondralossification, or both, thereby becoming visible radiographically. Theother cartilages are elastic in type.

The thyroid cartilage (fig. 53-9) comprises two spring-like plates termedlaminae, which are fused anteriorly but divergent posteriorly. Thelaminae produce a median elevation termed the laryngeal prominence("Adam's apple"), which is palpable and frequently visible.The posterior border of each lamina is prolonged superiorly andinferiorly ascornua, or horns. The superior horn is anchored to the tip of thegreater horn of the hyoid bone. The inferior horn articulates mediallywith the cricoid cartilage. The lateral surface of each lamina iscrossed by an oblique line for the attachment of muscles.

The cricoid cartilage (fig. 53-9) is shaped like a signet ring. It comprises aposterior plate, called the lamina, and a narrow, anterior part, thearch. Thelamina articulates superolaterally with the arytenoid cartilages. Thecricoid cartilage is at the level of the C6 vertebra, and its arch ispalpable. The inferior border of the cricoid cartilage marks the end ofthepharynx and larynx and hence the commencement of the esophagus andtrachea.

The arytenoid cartilages (fig. 53-9B)articulate with the superior border of the lamina of the cricoidcartilage. Each has a superiorly-positioned apex (which supports thecorniculatecartilage) and a base that comprises its inferior part. The base sendsa vocal process anteriorward(for attachment to the vocal ligament) and a lateral, muscular process(for muscular attachments). The corniculate and (inconstant) cuneiformcartilages are nodules in the aryepiglottic folds (figs. 53-10B and53-12).

The epiglottic cartilage (see fig. 53-9) iscovered by mucous membrane to form the epiglottis. The epiglottisis situated posterior to the root of the tongue and the body of thehyoidbone and anterior to the inlet of the larynx. The inferior end, orstalk, of the leaf-shaped cartilage is anchored to the posterior aspectof thethyroid cartilage. Taste buds are present in the posterior surface ofthe epiglottis.

Joints (fig. 53-9)

Two synovial joints are present on each side. The cricothyroid joint,between the lateral aspect of the cricoid cartilage and the inferiorhorn of thethyroid cartilage, allows mainly rotation of the thyroid cartilagearound a horizontal axis through the joints of the two sides. Thisproduces a tipping motion where the anterior part of the thyroidcartilage moves anterior and inferior. Thecricoarytenoid joint, between the superior border of the lamina of thecricoid cartilage and the base of the arytenoid cartilages, allowsgliding and rotation of the arytenoid cartilages.

Ligaments

The thyrohyoid membrane connects the thyroid cartilage with thesuperiorborder of the hyoid bone (see fig. 53-9C). Themedian part is thickened to form a ligament. The membrane is pierced oneach side by the internal laryngeal nerve and the superior laryngealvessels.

The cricothyroid ligament (see fig. 53-8) connects the arch of the cricoid cartilage with the thyroid cartilage. The term conus elasticus (fig. 53-10A) is used for elastic fibers that extend superiorward from the cricoid cartilage to the vocal ligaments (cricovocal membrane). In acute respiratory obstruction, cricothyrotomy, that is, entering the larynx between the arch of the cricoid cartilage and the thyroid cartilage by penetrating the cricothyroid membrane, is preferable to tracheotomy for the non-surgeon.

The vocal ligament on each side extends posteriorward from its anteriorattachment on the thyroid cartilage to a posterior attachment onthe vocal process of the arytenoid cartilage. This "vocal cord" is theupper border of the conus elasticus. The vocal cords are composed ofelastic fibers covered tightly by a vocal fold of mucousmembrane (fig. 53-10B). The vestibular ligament on each side isan indefinite band situated superior to the vocal ligament and coveredloosely by the vestibular fold.

The epiglottis is attached by ligaments to the hyoid bone, to theposterior aspect ofthe tongue, to the sides of the pharynx, and to the thyroid cartilage.

Inlet

The inlet, or aditus, of the larynx is the passageway from thelaryngopharynxinto the cavity of the larynx. It is set obliquely, facing largelyposteriorward. It is bounded anteriorly by the superior border of theepiglottis, on each side by the aryepiglottic folds, and inferiorly andposteriorly by an interarytenoid fold (fig. 53-11C).The inlet is related laterally to the piriform recesses of thelaryngopharynx (see fig. 53-3). The aryepiglottic folds provide lateralfood channels that lead along the sides of the epiglottis, through thepiriform recesses, and to the esophagus (fig. 53-12).Closure of the inlet protects the respiratory passages against theinvasion of food and foreign bodies. This closure is produced bycontraction of the aryepiglottic and transverse arytenoid muscles andby the posterior motion of the epiglottis that is produced by theelevation of the larynx. This elevation raises the base of theepiglottis more than the superior portions, resulting in a posteriortilting of the epiglottis.

Cavity

The cavity of the larynx is divided into three portions: (1) thevestibule; (2) the ventricles and the area between them; (3) and theinfraglottic cavity. These regions are defined by the location ofhorizontal folds - the vestibularand the vocal folds (see fig. 53-10).

(1) The vestibule extends from the inlet to the vestibular folds.

(2) The ventricle extends laterally in the interval between thevestibular and vocal folds. Each ventricle resembles a canoe laid onits side, and the two ventricles communicate with one another throughthe medianportion of the laryngeal cavity. A small diverticulum, the saccule,which extends superiorward from the anterior aspect of each ventricle,possesses mixedglands and has been termed the "oil can" of the vocal folds. Thevestibular folds (see fig. 53-10A and B), or "false vocal cords," contain thevestibular ligaments and are protective rather than vocal in function. Thevocal folds, or "vocal cords," which contain the vocal ligaments,are musculomembranous shelves that appear inferior and medial to thevestibular folds.They extend from the angle of the thyroid cartilage in the anteriorlarynx to its posterior attachment on thevocal processes of the arytenoid cartilages. The bulk of eachvocal fold is formed by the vocalis muscle, which is a part of thethyro-arytenoid muscle. The vocal folds and processes, together withthe interval (rima glottidis) between them, are collectively termed theglottis. The rima glottidis is the narrowest part of the laryngealcavity and can be seen between the more separated vestibular foldsduring laryngoscopy (see fig. 53-11D).The mucous membrane over each vocalligament has nonkeratinizing, stratified squamous epithelium, isfirmly bound down, and appears white. The vocal folds control thestream of air passing through the rima and hence are important in voiceproduction. The anterior, intermembranous part of the rima lies betweenthe vocal folds, whereas the posterior, intercartilaginous part issituated between the arytenoid cartilages (see fig. 53-14).The shape and size of the rima are altered by movements of thearytenoid cartilages. The rima is wider during inspiration and quietbreathing and narrower during expiration and phonation. In surfaceanatomy, the rima glottidis is approximately on the level of themidpoint of the anterior margin of the thyroid cartilage.

(3) The infraglottic cavity extends from the rima glottidis to thetrachea.

Closure

Three levels or tiers in the larynx can be closed by sphinctericmuscles: (1) the inlet, which is closed during deglutition and protectsthe respiratory passages against the invasion of food; (2) thevestibular folds, closure of which traps air in the trachea andmakespossible an increase of intrathoracic pressure (as in coughing) orintra-abdominal pressure (as in micturition and defecation); and (3)the vocal folds, which are approximated in phonation. The presenceof a foreign body is the commonest cause of laryngeal spasm, whichusually involves not only the glottis but all of the sphinctericmusculature of the larynx.

Mucous membrane

The mucosa of the larynx, which is continuous with that of thelaryngopharynx and trachea, is loose except over the posterior part oftheepiglottis and over the vocal ligaments. Hence this membrane may becomeraisedabnormally by submucous fluid, as in edema of the larynx. Theedema does not spread inferior to the level of the vocal folds, sinceit is limitedby the tight attachment of the mucosa to the vocal ligaments.

Sensory innervation andblood supply

The mucosa of the larynx is supplied on each side chiefly by theinternal laryngeal branch of the superior laryngeal nerve, whichsupplies the larynx as far down as the vocal folds. The inferiorpartof the larynx receives sensory fibers from the recurrent laryngealnerve.

The larynx has arterial supply by (1) the superior laryngeal artery(from thesuperior thyroid), which accompanies the internal laryngeal nerve, and(2) the inferior laryngeal artery (from the inferior thyroid), whichaccompanies the recurrent laryngeal nerve.

Muscles of larynx

The larynx as a whole can be elevated and depressed by extrinsicmuscles (e.g., the stylopharyngeus and palatopharyngeus and theinfrahyoid muscles).

The intrinsic laryngeal muscles are complicated, but they may beclassified as follows:

1. The sphincters of the inlet: transverse arytenoid; obliquearytenoid and aryepiglottic.

2. The muscles that close and open the rima glottidis: lateralcricoarytenoid (adductor) and posterior cricoarytenoid (abductor).

3. The muscles that regulate the vocal ligaments: thyroartenoidand vocalis; cricothyroid.

The muscles of the larynx are illustrated in figures 53-13 and 53-14D andsummarized in table 53-2.

Three muscles arise from the cricoid cartilage: the cricothyroid,arising from the lateral aspect of the cricoid cartilage and passingposteriorward to insert on the lamina and inferior horn of the thyroidcartilage; the lateral cricoarytenoid, extending posteriorward to themuscular process of the arytenoid cartilage; and the posteriorcricoarytenoid, extendinglaterally to the muscular process of the arytenoid cartiage (fig. 53-13).Two muscles, closely related to each other, connect the thyroid andarytenoid cartilages: the thyroarytenoid and the vocalis (fig. 53-14D).Two muscles unite the arytenoid cartilages: the transverse and obliquearytenoids (fig. 53-13D).

Abduction of the vocal cords is carried out solely by the posteriorcrico-arytenoid muscles, which, extending laterally from the posterioraspect ofthe cricoid cartilage to the muscular processes, rotate the arytenoidcartilages laterally (fig. 53-14B and C). Abduction widens the gap ofthe glottis(batween the vocal cords), which is necessary for respiration.Adduction of the vocal cords is carried out by thelateral cricoarytenoid muscles, which, extending posteriorward from thearch of the cricoid cartilage to the muscular processes, rotate thearytenoid cartilages medially (fig. 53-14D).This closes the glottis, as inphonation (fig. 53-14A, B and C). The oblique and transversearytenoid muscles are needed in order to maintain approximation of theposterior portions of the vocal cords. After closure of the glottis,the vocal folds can be tightened and lengthened by the cricothyroidmuscles to change the pitch and tone of the voice. The cricothyroidmuscle, by tipping the thyroid cartilage anterior on the cricoidcartilage will increase the anteroposterior dimension of the larynx andtighten the vocal cord.

Motor innervation

All of the intrinsic muscles, with the exception of thecricothyroid,are supplied by the recurrent laryngeal nerve from the vagus. Thecricothyroid is supplied by the external laryngeal branch of thesuperior laryngeal nerve from the vagus. The motor nerve fibers of the variouslaryngeal muscles are believed to originate from the brain as a cranial part of the accessory nerve before joining the vagus prior to leaving the skull. Unilateral damage of arecurrent laryngeal nerve results in paralysis of all the intrinsicmuscles of the larynx except the cricothyroid, which will tend toadduct the vocal cord.

Additional reading

Jackson, C., and Jackson, C. L., Diseases of the Nose, Throat, and Ear,2nd ed., W. B. Saunders Company, Philadelphia, 1959. This classic textcontains an interesting chapter on laryngeal paralyses.

Tucker, G. F., Human Larynx. Coronal Section Atlas, Armed ForcesInstitute of Pathology, Washington, D.C., 1971. Black-and-whitephotomicrographs with labels.

Questions

53-1 Anterior to which vertebrae is thepharynx situated?

53-1 The pharynx is situated anterior tocervical vertebra 1 to 6 (see fig. 53-1).Occasionally the nasopharynx andlaryngopharynx are referred to as the epipharynx and hypopharynx,respectively. Similarly, the epitympanic recess and the tympanic cavityinferior to the level of the tympanic membrane are sometimes called theepitympanum and hypotympanum, respectively.

53-2 What is the nasopharynx?

53-2 The nasopharynx is the superiormostpartof the pharynx, but (at least in its anterior aspect) it may also beregarded as the posterior portion of the nasal cavity (F. W. Jones, J.Anat., 74:147,1940; K. Leela, R. Kanagasuntheram, and F. Y. Khoo, J.Anat., 117:333, 1974).

53-3 What are the boundaries of thepharyngeal isthmus?

53-3 The pharyngeal isthmus (between thenasopharynx and oropharynx) is bounded by the soft palate,palatopharyngeal arches, and posterior wall of the pharynx.

53-4 What are adenoids?

53-4 Adenoids (Gk, gland-like) arehypertrophied (naso)pharyngeal tonsils on the posterior wall of thenasopharynx. They may cause respiratory obstruction. Their removal(adenoidectomy), which was first undertaken in 1868, is generallycombined with tonsillectomy.

53-5 What is the pharyngeal hypophysis?

53-5 The pharyngeal hypophysis, situatedonthe posterior wall of the pharynx, develops at the pharyngeal end ofthe stalk of the craniopharyngeal pouch (Rathke, 1838). Like the sellarhypophysis, it is an endocrine gland (P. McGrath, J. Endocrinol.,42:205, 1968) and contains several types of secretory cells (C. B.Gonzalez, G. F. Valdes, and D. R. Ciocca, Acta Anat., 97:224, 1977).

53-6 Where are the openings of theauditory tube?

53-6 The so-called auditory tube,describedby Eustachi (1563) but known even before the time of Christ, would bebetter named the pharyngotympanic tube. Its cartilaginous part is adiverticu1um of the pharynx that opens posterior to the inferior nasalconcha(see fig. 53-4).The osseous part is a prolongation of the tympanic cavity opening fromtheanterior wall of the cavity. The tube is closed at rest but opensduring swallowing and phonation, perhaps by a "milking" action of thelevator and tensor (S. Seifand A. L. Dellon, Cleft Palate J.,15:329,1978; see also V. K. Misurya, Arch. Otolaryngol., 102:265,1976). A detailed account of the tube is available in J. Terracol,A. Corone, and Y. Guerrier, La trompe d'Eustache,'Masson, Paris, 1949.

53-7 What are the boundaries of thefaucial isthmus?

53-7 The faucial (or oropharyngeal)isthmusis bounded by the soft palate, palatoglossal arches, and tongue.

53-8 List the components of the pharyngeallymphatic ring.

53-8 The pharyngeal lymphatic ring(Waldeyer, 1884) comprises the nasopharyngeal, tubal, palatine, andlingual tonsils. It is presumed to be a protective collar againstinfections and organisms that might enter through the nose and mouth.

53-9 Where is the tonsil?

53-9 The (palatine) tonsils are locatedbetween diverging pillars on each side of the pharynx, namely thepalatoglossal and palatopharyngeal arches. Tonsillectomy, an operationdescribed by Celsus in the first century A.D., is now performed eitherby dissection or by a special instrument known as a guillotine.

53-10 What is the piriform recess?

53-10 The piriform recess (or sinus orfossa), in which foreign bodies may become lodged, is the part of thecavity of the laryngopharynx situated on each side of the inlet of thelarynx (see fig. 53-3).

53-11 Where does a pharyngealdiverticulum usually form?

53-11 A pharyngeal diverticulum usuallyforms posteriorly through the fibers of the inferior constrictor(between the thyropharyngeal and cricopharyngeal fibers). Increasedintrapharyngeal pressure is regarded as an important factor in theproduction of a "pulsion diverticulum" through a weak area ("Killian'sdehiscence") between the parts of the inferior constrictor. Moreover,swallowing in the presence of cricopharyngeal incoordination may beimportant in allowing mucosal herniation through a weak area in thepharyngeal wall (W. S. Payne and A. M. Olsen, The Esophagus, Lea &Febiger, Philadelpha, 1974). Regurgitation and difficulty in swallowing(dysphagia) may result, so that surgical excision may be indicated.Normally, a sphincteric zone is described immediately inferior to it,althoughalso supplemented by, the inferior constrictor (C. Zaino et al., ThePharyngoesophageal Sphicter, Thomas, Springfield, Illinois, 1970).

53-12 What is the motor innervation ofthe pharynx?

53-12 The motor innervation of thepharynxis chiefly through the pharyngeal plexus, which is formed by thepharyngeal branches of cranial nerves X and IX. The vagus nerveprovides most of the motor innervation. These motor fibers are derivedfrom the accessory nerve. The glossopharyngeal nerve is mostly sensory.

53-13 How may the interior of the larynxbe viewed in vivo?

53-13 The interior of the larynx may beviewed in vivo either indirectly through a laryngeal mirror or directlythrough a laryngoscope (see figs. 53-11C andD and 53-12).During the nineteenth century, the stethoscope, ophthalmoscope,laryngoscope, gastroscope, cystoscope, rectoscope, and bronchoscopewere invented, in that order.

53-14 What is the vertebral levelcorresponding to the inferior extent of the larynx?

53-14 The larynx ends opposite the C6vertebra,where the pharynx and larynx become continuous with the esophagus andtrachea, respectively.

53-15 Is the hyoid bone a part of thelarynx?

53-15 The hyoid bone is generally notincluded as a part of the larynx. The larynx is suspended from thehyoid bone, which is in turn suspended from the base of the skull. Thestyloid process, usually 30 mm in length, may be as long as 80 mm. Thestylohyoid ligament, which connects it to the lesser horn of the hyoidbone, may become partly or even completely calcified, or it may becomea chain of ossicles (J. R. Chandler, Laryngoscope, 87:1692, 1977).

53-16 Are the arytenoid cartilages fixedor mobile?

53-16 The arytenoid cartilages areextremely mobile. Arytenoid means shaped like a vase.

53-17 Where are the corniculate andcuneiform cartilages?

53-17 The corniculate cartilages(Santorini, 1724) are in the aryepiglottic folds and on the apices ofthe arytenoid cartilages, with which they form aposteriorward-projectinghorn (or cornu; hence the name). The cuneiform cartilages (Wrisberg,1786) are also in the aryepiglottic folds, immediately anterior to thecorniculate. These cartilages form elevations that may be visible onlaryngoscopy (see fig. 53-12). A small, unimportant nodule in theposterior border of the thyrohyoid membrane is known as the cartilagotriticea (L., grain-like).

53-18 How may the larynx be entered inacute respiratory obstruction?

53-18 In acute respiratory obstruction,the infraglottic cavity may be entered through the cricothyroidligament (cricothyrotomy).

53-19 Why have the vestibular folds beentermed "false vocal cords"?

53-19 The vestibular folds arefrequentlyreferred to as "false vocal cords" because they do not produce voicesounds.

53-20 Which is the narrowest part of thelaryngeal cavity?

53-20 The rima glottidis, i.e., theinterval between the vocal folds, is the narrowest part of thelaryngeal cavity.

53-21 What is the commonest cause oflaryngeal spasm?

53-21 The presence of a foreign body isthe commonest cause of laryngeal spasm.

53-22 Why does laryngeal edema not extendinferior to the glottis?

53-22 Mucosal swelling does not spreadinferior to the glottis because the mucosa is closely adherent to thevocalfolds.

53-23 What are the afferent fibersinvolved in the cough reflex?

53-23 Afferent vagal fibers from thelarynx (superior laryngeal nerves), trachea, and bronchi reach themedulla. Then a deep inspiration is followed by closure of the vocalfolds, forceful expiration, and sudden opening of the vocal folds.Foreign matter is usually removed by the rapidly moving air.

53-24 What are the results of injury(e.g., during thyroid surgery) to a recurrent laryngeal nerve?

53-24 Unilateral severance of arecurrentlaryngeal nerve causes paralysis of the intrinsic muscles, except forthe cricothyroid. However, the abductor (posterior cricoarytenoid) isusually affected first (Semon's rule), so that the involved vocal foldremains in the median plane, except when jostled by the normal fold(Chevalier Jackson). The voice is usually hoarse, as was shownexperimentally in the dog by Galen in the second century.

Figure legends

Figure 53-1General arrangement of the major parts of the pharynx as seen in amedian section.

Figure 53-2Scheme of respiratory and digestive cavities in the head and neck. Notethat the pharynx acts as a common channel for both respiration anddeglutition and that the air and food passages cross each other. (AfterBraus.)

Figure 53-3Anterior wall of the pharynx viewed from the posterior aspect. Thepharynxcommunicates with the nasal cavity, auditory tubes, oral cavity,larynx, and esophagus.

Figure 53-4Sagittal (almost median) section of the head and neck, with a portionof the brain included. The various structures shown in thisillustration have been given labels in other figures. Note thehypophysis, corpus callosum, septum pellucidum, pineal body, thirdventricle, aqueduct, fourth ventricle, pons, cerebellum, medulla, andspinal cord; C1 to 7 vertebra as well as the T1 vertebra; the frontaland sphenoidal sinuses;the nasal conchae, palate, and opening of the auditory tube; thegenioglossus and geniohyoid muscles; the larynx and trachea and pharynxand esophagus.

Figure 53-5View of the right lateral wall of the nasopharynx from the medial side.See figure 53-4fororientation.

Figure 53-6A, Right palatine tonsil and its surroundings, medial aspect. B,Horizontal section through the tonsil, at a greater magnification.(After Fetterolf.)

Figure 53-7Muscles of the pharynx. A, posterior aspect. B, right lateral aspect.

Figure 53-8The structures in or near the anterior median line of the neck: (1)symphysis menti, (2) diaphragma oris (mylohyoid muscles) crossed by thedigastric muscles, (3) hyoid bone, (4) median thyrohyoid ligament, (5)laryngeal prominence of the thyroid cartilage (overlying the glottis),(6) cricothyroid ligament, (7) arch of the cricoid cartilage, (8)cricotracheal ligament, (9) trachea and isthmus of the thyroid gland,(10) inferior thyroid veins forming a plexus, (11) jugular arch unitingthe right and left jugular veins, (12) thymus (chiefly in childhood)and occasionally part of the brachiocephalic trunk or of the leftbrachiocephalic vein, and (13) jugular notch of the manubrium sterni.The infrahyoid muscles are not shown here.

Figure 53-9The larynx. A, B, and C, Anterior, posterior, and right lateral viewsof cartilages. D, Right anterolateral aspect, showing the planes ofsection of figure 53-10. Note the thyroid and cricoid cartilages andthe hyoid bone and epiglottic cartilage in A to D and the arytenoidcartilages in B.

Figure 53-10A, Coronal and, B, median views of the larynx.

Figure 53-11Ear, nose, and throat in vivo. A, The right tympanic membrane, showingthe handle of the malleus. Cf. fig. 44-2. B, The nasopharynx and nasal cavities asseen in a mirror placed on the posterior pharyngeal wall. Note theposterior edge of the nasal septum, inferior nasal concha, and (on theright side of the illustration) the opening of the auditory tube. Cf.fig. 52-4. C,The larynx on inspiration, as seen in a mirror placed on the posteriorpharyngeal wall. Note the epiglottis, ary-epiglottic folds, and (on theleft side of the illustration) cuneiform cartilage, vestibular andvocal folds, and trachea. Cf. fig. 53-2. D,The larynx on phonation, as seen in a mirror. Note the vestibular andvocal folds: the latter are now approximated. (All photographs courtesyof Paul H. Holinger, M.D., Chicago, Illinois.)

Figure 53-12Indirect laryngoscopy. A shows the placement of the mirror in thepharynx. B shows the structures seen during respiration. The upper partof the trachea can be seen through the open glottis. Cf. Fig. 53-11C.

Figure 53-13Intrinsic muscles of the larynx. A and B, Right lateral aspect of thethyroid and cricoid cartilages. C, Medial aspect of the right half ofthe thyroid and cricoid cartilages. D, Posterior aspect of thearytenoid and cricoid cartilages.

Figure 53-14The rima glottidis (in yellow) and the vocal ligaments in (A)phonation, (B) forced inspiration, and (C) quiet respiration. Note therotation and lateral sliding of the arytenoid cartilages and thedifferent shapes of the glottis. D, Muscles of the larynx seen fromthe superior aspect. The white arrows L and P show the direction ofaction of thelateral and posterior crico-arytenoid muscles, respectively. The blackarrows show the direction of action of the transverse arytenoid muscle.M, muscular process of the arytenoid cartilage; V, vocal process of thearytenoid cartilage. It should be noticed that the apex of the A formedby the vocal ligaments is located anteriorly.

* The existence of a pterygomandibularraphe between the superior constrictor and buccinator has been deniedby G. R. L. Gaughran (Anat. Rec., 184:410, 1976).