Respiratory System: Nasal Part - PDF

Nasal part of frontal bone NOSE...

Nasal part of frontal bone NOSE Nasal bone -Frontal process of maxilla The nose the part of the respiratory tract superior to the is Lateral process hard palate and contains the peripheral organ of smell. It -Accessorynasal cartilage includes the external nose and nasal cavity, which is divided Septal nasal cartilage into right and left cavities by the nasal septum (Fig.7.101A). The functions of the nose include olfaction (smeling), res -Majoralar cartilage piration (breathing), fltration of dust, humidifcation of Fibro-areolar tissue inspired air, and receptionand eliminationof secretions from the paranasal sinuses andnasolacrimalducts. Naris (nostril) External Nose (B) Anterior view The external nose is the visible portionthat projects from the face:its skeleton is mainly cartilaginous (Fig.7.101B). FIGURE 7.101. External nose. A. The surface anatomy of the nose is Noses vary considerablyin size and shape, mainly because shown.The nose is attached to the forehead by its root. The rounded bor der between the apex and the root is the dorsum. B. The cartilages of the of differencesin these cartilages. The dorsum of the nose nose are retracted inferiorly to expose the sesamoid cartilages. The lateral extends from theroot of the nose to the apex (tip) of the nasal cartilages are fixed by suturesto the nasal bones and are continuous nose, Theinferior the nose is pierced bytwo piri surface of with the septal cartilage. form (L. pear-shaped) openings, the nares(nostrils, ante rior nasal apertures),which are bound laterally by thealae (wings) of the nose. The superior bony part of the nose, the bony parts of the nasal septum. The cartilaginouspart of including its root, is covered by thin skin. the nose consists of five main cartilages: two lateral cartilages, The skin over the cartilages of the nose is covered with cartilage. The U-shaped alar two alar cartilages, andone septal thickerskin,which contains many sebaceous glands.The skin cartilages are free and movable; they dilate or constrict the extends into thevestibule of the nose (Fig.7.103A),where nareswhen the muscles acting on the nose contract. it has a variable number of stiff hairs (vibrissae). Because they are usually moist, these hairs filter dust from particles NASAL SEPTUM air entering the nasal cavity. The junction of the skin and The nasal septum divides thechamber of the nose into two mucous membrane is beyond the hair-bearing area. nasal cavities. The septum has a bony part and a soft mobile SKELETON OF EXTERNALNOSE cartilaginous part. The main components of the nasal sep tum are the perpendicular plate of the ethmoid, the vomer, The supporting skeletonof the nose is composed of bone and and the septal cartilage. The thin perpendicular plate of hyaline cartilage. The bony part thenose (Figs. 7.101B and of the ethmoid bone, forming the superior part of the nasal 7.102)consists of the nasal bones,frontalprocesses themax of septum, descends from thecribrifornplate and is continued illae, the nasalpart ofthe frontal bone and its nasalspine,and superiorto this plate as the cristagalli. The vomer, a thin 985/1170  Bones: Frontal Ethmoid Nasal Palatine Maxilla Sphenoid Inferior concha Vomer Cribriform plate of Crista galli Perpendicular Sphenopalatine ethmoid bone foramen plate of ethmoid Frontal bone Crest of bone sphenoid Superior concha bone Nasal bone Superior meatus Nasal spine of Middle concha frontal bone Medial Frontal process pterygoid Septal Lacrimal bone Vomer plate cartilage Middle meatus -Horizontal Inferior concha plate of Vomeronasal palatine Inferior meatus bone cartilage Nasal crest of Palatine Pterygoid palatine bone Nasal crest of maxilla process hamulus of maxilla (A) Lateral wall of nasal cavity (B) Nasal septum Medial view Lateral view FIGURE 7.102. Lateral and medial (septal) walls of right side of nasal cavity. The walls are separated and shown as adjacent pages of abook. The medial view shows the right lateral wall the nasal cavity, and the lateral view shows the nasal septum. The nasal septum has a hard (bony)part located of deeply (posteriorly) where it is protected and a soft or mobile part located superficially (anteriorly) mostly in the more vulnerable external nose. lat bone, forms the postero-inferiorpart of the nasal septum, BOUNDARIES OF NASAL CAVITIEs with some contribution from the nasal crests of the maxillary The nasal cavities have a roof, Hoor, and medial and lateral and palatine bones. The septal cartilage has a tongue-and walls. groove articulation with the edges of the bony septum. The roofof the nasal cavities is curved and narrow, except Nasal Cavities at its posterior end, where the hollow body ofthe sphenoid forms the roof. It is divided into three parts (frontonasal, The term nasal cavity refers to either the entire cavity or to ethmoidal, and sphenoidal) named from the bones form the right or left half, depending on the context. The nasal ing each part (Fig. 7.102). cavity is entered anteriorly through the nares (nostrils). It The floor of the nasal cavities is wider than the roof and opensposteriorly into the nasopharynx through the choanae is formedby the palatine processes of the maxilla and the (Fig. 7.9). Mucosa lines the nasal cavity, except for the nasal horizontal plates of the palatine bone. vestibule, which is lined with skin (Fig. 7.103A). The medial wall of the nasal cavities is formedby the nasal The nasal mucosa firmly bound to the periosteum septum. and perichondrium of the supporting bones and cartilages The lateral walls the nasal cavities are irregular owing to of of the nose. The mucosa is continuous with the lining of all three bony plates, the nasal conchae, which project inferi the chambers with which the nasal cavities communicate: orly, somewhatlike louvers (Figs. 7.102A, 7.103, and 7.108). the nasopharynx supe posteriorly, the paranasal sinuses riorly and and the lacrimal sac and conjunctiva laterally, FEATURES OF NASAL CAVITIES superiorly. The inferior two thirds of the nasal mucosa is the respiratory area, and the superior one third is the olfactory The nasal conchae (superior, middle, and inferior) curve area (Fig. 7.106B). Air passing over the respiratory area inferomedially, hanging like louvers or short curtains from iswarmed and moistened before it passes through the rest the lateral wal. The conchae (L. shells) or turbinates of many of theupper respiratory tract to the lungs. The olfactory mammals (especially running mammals and those existing in area contains the peripheral organ of smell; sniffing draws extreme environments) are highly convoluted, seroll-like struc air to the area. tures that offer a vast surface area for heat exchange. In both 986/1170 humans with simple plate-like nasal conchaeand animals with When infected or irritated, the mucosa covering the conchae complex turbinates,a recess or nasal meatus (singularand may swell rapidly, blocking the nasal passage(s) on that side. plural; passage(s)in the nasal cavity) underlies each of the bony The spheno-ethmoidalrecess, lying superoposterior to formations. The nasal cavity is thus divided into five passages: the superior concha, receives the opening of the sphenoidal a posterosuperiorly placed spheno-ethmoidal recess, three lat sinus, an air-filled cavity in the body of the sphenoid. The erally located nasal meatus (superior,middle, and inferior), superiornasal meatus is a narrow passage between the and a medially placed common nasal meatus into which the superior and the middle nasal conchaeinto which the pos The inferior concha is the longest four lateral passages open. terior ethmoidal open by one or more orifices (Fig. sinuses and broadest of the conchae and is formed by an independent 7.103A). The middle nasal meatus is longer and deeper bone (of thesame name, inferior concha) covered byamucous than the superior one. The anterosuperior part of this pas membrane that contains large vascular spaces that can enlarge sage leads into a funnel-shaped opening, the ethmoidal to control the caliber of the nasal cavity. The middle and infundibulum,through which it communicateswith the superior conchae are medial processes tlhe ethmoid bone. of frontal sinus (Fig. 7.104). The passage that leads inferiorly Supra-orbital nerve and artery Levator palpebrae superioris Frontal sinus (F) -Superiorrectus Lacrimal gland Crista galli (CG) Check ligament Superior oblique -Eyeball Medial rectus -Lateral rectus Ethmoidal infundibulum -Inferior oblique Ethmoidal air cells (E) Air cell in middle concha -Inferior rectus Semilunarhiatus Middle meatus R Infra-orbital vessels and nerve Opening of maxillary sinus A Maxillary sinus (M) Walls of maxillary sinus: Inferior meatus A Apex FL Floor Inferior concha B B Base R Roof Nasal septum FL, Hard palate (HP) Oral cavity (0C) First molar F tooth (A)Posterior view CG E E M HP (B)Anteroposteriorview FIGURE.104. Coronal section of right half of head. A.The orientation drawing illustrates the plane of the section. Observe the relationship of the orbit, nasal cavity, and paranasal sinuses. The orbital contents, including the four recti and the fascia uniting them, form a circle (a cone when viewed in three dimensions) around the posterior part (fundus) of the eyeball. B. Radiograph of cranium demonstrating nasal cavity and paranasal sinuses. Letters refer to structures labeled in part A. 988/1170 from each frontal sinus to the infundibulum is the fronto anteriorpart of the nasal septum is the site of an anastomotic nasal duct (Fig. 7.103B). The semilunar hiatus (L. hiatus arterial plexus involving al five arteries supplying the septum semilunaris) isa semicircular groove into which the frontal (Kiesselbacharea). The external nose also receives blood from sinus opens. The ethmoidal bulla (L. bubble), a rounded first and fifth arteries listed, plus nasal branches of the infra elevation located superior to the semilunar hiatus, is visible orbital artery and the lateral nasal branches of the facial artery. when the middle concha removed. The bulla is formned by is A rich submucosal venous plexus, deep to the nasal middle ethmoidal cells that form the ethnoidal sinuses. mucosa, provides venous drainage of the nose via the spheno The inferior nasal meatus is a horizontal passage infero palatine, facial, and ophthalmic veins. The plexus is an impor lateral to the inferior nasal concha. The nasolacrimnal duct, tant part of the body's thermoregulatory system, exchanging which drains tears from the lacrimal sac,opens into the ante heat and warmingair before it enters the lungs. Venousblood rior part of this meatus (see Fig. 7.46A, p. 892). The com from the external nose drains mostly into the facial vein via mon nasal meatus is the medial part of the nasal cavity the angular and lateral nasal veins (see Fig. 7.25). However, between the conchae and the nasal septum,into which the recall that it lies within the danger area" of the face because lateral recesses and meatus open. of communications with the cavernous (dural venous) sinus (see the blue box "Thrombophlebitis of Facial Vein," p. 875). Regardingits nerve supply ofthenose, the nasal mucosacan Vasculature and Innervation of Nose be divided into postero-inferiorand anterosuperior portions The arterial supply of the medial and lateral walls of the by an oblique line passing approximately through the ante nasal cavity (Fig. 7.105) is from five sources: rior nasal spine and the spheno-ethmoidal recess (Fig.7.106). The nerve supply of the postero-inferiorportion of the nasal 1. Anterior ethmoidal artery (from the ophthalmie artery). mucosa is chiefly from the maxillary nerve, by way of the 2. Posterior ethmoidal artery (from the ophthalmic artery). nasopalatine nerve to the nasal septum, and posterior supe 3. Sphenopalatine artery (from the maillary artery). rior lateral nasal and inferior lateral nasal branches of the 4. Greater palatine atery (fromthe maxillary artery). greater palatine nerve to the lateral wall. The nerve supply 5. Septal branch of thesuperior labial artery (from the facial of the anterosuperior portion is from the ophthalmic nerve artery). (CN V)byway of the anterior and posterior ethmoidal The first three arteries divide into lateral and medial (septal) nerves, branches of the nasociliary nerve. Most of the exter branches. The greater palatine artery reaches the septum nal nose (dorsumand apex) is also supplied by V,(via CN via the incisive canal through the anterior hard palate. The the infratrochlearnerve and the external nasal branch of the Sphenopalatine Posterior Posterior Anterior artery ethmoidal ethmoidal Branch of ethmoidal traversing arteries arteries arteries Anterior sphenopalatine sphenopalatine ethmoidal foramen artery Kiesselbach arteries area (orange, rich in anastomosing arteries) Lateral nasal Incisive canal branches of facial artery Septal branch of superior a Greater labiallartery Branches of Greater palatine palatine sphenopalatine artery artery artery (A) Lateral wall of nasal cavity (B) Nasal septum Open-book view FIGURE7.105. Arterial supply of nasal cavity. An open-book view of the lateral and medial walls of the right side of the nasal cavity is shown.The left "page" shows the lateral wall the nasal cavity. The sphenopalatine artery (a branch ofthe maxillary) and the anterior ethmoidal artery (a branch of the oph of thalmic) are the most important arteries to the nasal cavity. The right "page"shows the nasal septum. An anastomosis of four to five named arteries supplying the septum occurs in the antero-inferior portion of the nasal septum (Kiesselbach area, orange), an area commonly involved in chronic epistaxis (nosebleeds). 989/1170  Anterior Olfactory nerves in Olfactory Pterygopalatine olfactory epithelium ethmoidal nerve bulb ganglion Anterior Olfactory ethmoidal nerve Nasal branch of ,Maxillary mucosa nerve anterior superior (purple) ,Internal nasal alveolar nerve branch of -Nerve of infra-orbital nerve CN V, pterygoid CNV, Internal -CN V2 canal CN.V, nasal branch of infra-orbital Incisive canal nerve Nasopalatine nerve Greater Nasopalatine Lesser Lesser nerve palatine nerve Pharyngeal palatine Greater palatine nerve nerve nerve palatine nerve (A) Lateral wall of nasal cavity (B) Nasal septum Open-book view FIGURE7.106. Innervation of nasal cavity. An open-bookview of the lateral and medial (septal) walls ofthe right side of the nasal cavity is shown. A dashed line extrapolated approximately from the spheno-ethmoidal recess to the apex of the nose demarcates the territories of the ophthalmic (CN V,) and maxillary (CN V) nerves for supplying general sensation to both the lateral wall and the nasal septum. The olfactory nerve (CN is distributed to the I) olfactory mucosa superior to the level of the superior concha on both the lateral wall and the nasal septum. anterior ethmoidal nerve), but the alae of the nose are sup in the median plane. The frontal sinuses vary in size from plied by the nasal branches of the infra-orbital nerve (CN V). approximately 5 mm to large spaces extending laterally into The olfactory nerves, concermed with smell, arise from cells the greater wings of the sphenoid. Often a frontal sinus has in the olfactory epithelium in the superior part of the lat two parts: a vertical part in the squamouspart of the frontal eral and septal walls of the nasal cavity. The centralprocesses bone, and a horizontal part in the orbital part of the frontal of these cells (forming the olfactory nerve) pass through the bone. One or both parts may be large or small. When the cribriform plate and end in the olfactory bulb, the rostral supra-orbitalpart is large, its roof forms the floorof the ante expansion of the olfactory tract (Fig. 7.102A). rior cranial fossa and its floor formsthe roof of the orbit. Paranasal Sinuses ETHMOIDALCELLS The paranasalsinuses are air-filled extensions of the respi The ethmoidal cells (sinuses) are small invaginations of the ratory part of the nasal cavityinto the following cranial bones: mucousmembrane of the middle and superiornasal meatus into frontal, ethmoid, sphenoid, and maxilla. They are named the ethmoid bone between the nasal cavity and the ortbit (Figs. according to the bones in which they are located. The sinuses 7.104, 7.107,and 7.108). The ethmoidal cells usually are not visi continue to invade the surrounding bone, and markedexten ble in plain radiographs before 2years age but are recognizable of sions are common in the crania of older individuals. in CT scans. The anterior ethmoidal cells drain directly or indi rectly into the middle nasal meatus through the ethmoidal infun FRONTAL SINUSES dibulum. The middle ethmoidal cells open directly into the middle meatus and are sometimes called "bullar cells" because Theright and left frontal sinuses are between the outer and they fon the etlhmoidal bulla, a swelling on the superiorborder inner tables of the frontal bone, posterior to the superciliary the semilunar hiatus (Fig. 7.103B). The posterior ethmoidal of arches and the root of the nose (Figs. 7.103, 7.104, and 7.107). cells open directly into the superiormeatus. The ethmoidal cells Frontal sinuses are usually detectable in children by 7 years of are supplied by the anterior and posterior ethmoidal branches of age.The right and left sinuseseach drain through a frontonasal the nasociliarny nerves (CN V)(Figs. 7.19 and 7.106). duct into the ethmoidal infundilbuhum,which opens into the semilunarhiatus the middle nasal meatus. The frontal sinuses of SPHENOIDAL SINUSES are innervated by branches of thesupra-orbitalnerves (CN V). The right and left frontal sinuses are rarely of equal size, The sphenoidal sinuses are located in the body of the and the septum betweenthem is not usuallysituated entirely sphenoid, but they may extend into the wings of this bone 990/1170  Chapter 7 Head 961 Ethmoidal cells (E) (blue) Right frontal sinus (F) (pink) Wall of optic canal Superciliary arch Left frontal sinus (pink) -Pituitary gland Recess in anterior clinoid process Lateral nasal cartilage Fullness over internal carotid artery Accessoryof Roof of pterygoid canal sesamoid cartilage Sphenoidal sinus (S) (yellow) Palatine fossa and palatine canal (dashed line below) Mobile part of nasal septum Maxillary sinus (M) (purple) Hard palate (HP) (A)Medial view of right side F E M HP (B) Left lateral radiograph P Pharynx FIGURE1.107. Paranasal sinuses I. A.The paranasal sinuses ofthe right side have been opened from a nasal approach and color coded. An anterior ethmoidal cell (pink) is invading the diploë of the frontal bone to become a frontal sinus. An offshoot (broken arrow) invades the orbital plate the frontal of bone. The sphenoidal sinus in this specimen is extensive, extending (1) posteriorly, inferior to the pituitary gland, to the clivus; (2) laterally, inferior to the optic nerve (CN ),into the anterior clinoid process; and (3) inferior to the pterygoid process but leaving the pterygoid canal and rising as a ridge on the floor of the The maxillary sinus is pyramidal. B. Radiograph sinus. of cranium demonstrating air densities (dark areas) associated with paranasal sinuses, nasal cavity, oral cavity, and pharynx. The letters are defined in part A. (Figs.7.103 and 7.107). They are unevenly divided and sepa posterior ethmoidal cellthat begins to invade the sphenoid at rated by a bony septum. Because of this extensive pneuma approximately 2years ofage. In some people, several posterior tization (formation of air cells), the body of the sphenoid is ethmoidal cells invade the sphenoid, giving rise to multiple fragile. Only thin plates of bone separate the sinuses from sphenoidal sinuses that open separately into the spheno several important structures: the optic nerves and optic chi ethmoidal recess (Fig.7.103A). The posteriorethmoidal arter asm,the pituitary gland, the internal carotid arteries, and the ies and the posterior ethmoidal nerves that accompanythe cavernous sinuses. The sphenoidal sinuses are derived from a arteries supply the sphenoidal sinuses (Fig.7.105). MAXILLARY SINUSES particularly the first two molars, often produce conical elevations in the loor of the sinus. The maxillary sinuses are the largest ofthe paranasal sinuses. They occupy the bodies of the maxillaeand communicate with Each maxillary sinus drains by one or more openings, the the middle nasal meatus (Figs.7.104, 7.107, and 7.108). maxillary ostium (ostia), into the middle nasal meatus of the nasal cavity by way of the semilunar hiatus. The apex of the maxillarysinus extends toward and often into the zygomatic bone. The arterial supplyof the maxillary sinus is mainly from superior alveolar branches of the maxillary artery The base of the maxillary sinus forns the inferior part of (Fig.7.73; Table 7.12); however, branches the descending the wall of the nasal cavity. of lateral and greaterpalatine arteries supply the floor tlhe sinus (Figs. The roof of the maxillary sinus is formed by the floor of of 7.98B). Innervation of the maxillary sinus is from the the orbit. anterior, middle, and posterior superior alveolar nerves, The floor of the maxillary sinus is formedby the alveo which are branches the maxillarynerve (Fig,. 7.79A). The of lar part of the maxilla. roots of the maxillary teeth, THE NOSE epistaxis (bleedingfrom the nose) usually occurs.In severe frac tures, disruption of the bones and cartilages results in displace Nasal Fractures ment ofthe When the injury nose. results from a direct blow,the cribriform plate ofthe ethmoid bone may also fracture. Because of the prominence of the nose, fractures of the nasal bones are common in automobile accidents and contact sports (unless ace guards are worm). Deviation of Nasal Septum Fractures usually result in deformation of the nose, particularly The nasal septum is usually deviated to one side or when a lateral force is applied by someone's elbow, for example; the other (Fig. B7.40). This could be the result of a birth injury, but more often the deviation occurs during adolescence and adulthood from trauma (e.g., during a fist Sometimes the deviation is so severe that the fight). nasal septum is in contact with the lateral wall of the nasal cavity and often obstructs breathing or exacerbates snoring, The deviation can be corrected surgically. Nasal septum deviated to left side Anterior view, CT scan Inferior view,MRI FIGURE B7.40. Deviated nasal septum. 993/1170  Respiratory Layer of Cervical Viscera The viscera ofthe respiratorylayer, the larynr and trachea, contribute to the respiratory functions of the body.The main Superiordeep cervical Prelaryngeal functions of the cervical respiratory viscera areas follows: deep cervical Inferior Paratracheal Submental Pretracheal Routing air and food into the respiratory tract and esopha Submandibular gus, respectively. Providing a patent airway and a means of sealing it off FIGURE 8.29. Lymphatic drainageof thyroid gland, larynx, and temporarily (a "valve"). trachea. The arrows indicate the direction oflymph flow. Producingvoice. 1051/1170 1022 Chapter8 Neck Epiglottis -0.3% Greater horn of -Internal laryngeal hyoid bone nerve External laryngeal nerve Inferior constrictor 0.3% Cricopharyngeus Sheath of thyroid 13% 11% gland 3% -Right lobe of thyroid gland Para Superior 1% 1.6% thyroid glands 20% 38% Inferior Parathyroid glands 1% -Inferior thyroid artery Esophagus Recurrent laryngeal nerve 6% Submucouscoat 4% of esophagus (A) Posterior view (B) Anterior view FIGURE 8.30. Thyroid and parathyroid glands. A. The thyroid sheath has been dissected from the posterior surface of the thyroid gland to reveal the three embedded parathyroid glands. Both parathyroid glands on the right side are rather low, and the inferior gland is inferior to the thyroid gland. B. Sites and frequencies aberant parathyroid glandular tissue are shown. of LARYNX inferior part of the pharynx (oropharynx)with the trachea. Although most commonly known forits role as the phonating The larynx is the complex organ of voice production (the mechanism for voice production, its most vital function is to "voice box")composed of nine cartilages connected by mem guard the air passages, especially during swallowing when it branes and ligaments and containing the cocal folds ("cords"). serves as the "sphincter" or "valve" of the lower respiratory The larynx is located in the anterior neck at the level of tract, thus maintaining a patent airway. the bodies of C3-C6 vertebrae (Fig. 8.31). It connects the  Laryngeal Skeleton. The laryngeal skeleton consists of The vocal ligaments make up the submucosal skeleton of the nine cartilages: three are single (thyroid,cricoid, and epiglot vocal folds. These ligaments are the thickened, free superior and three are paired tic), (arytenoid,corniculate,and cunei border of the conus elasticus or cricovocal membrane. form)(Fig.8.32A & B). The parts of the membrane extending laterally between the The thyroid cartilage is the largest of the cartilages; vocal folds and the superior border of the cricoid are the lat its superior border lies opposite the C4 vertebra. The infe eral cricothyroid ligaments. The fbro-elastic conus elasti rior two thirds of its two plate-like laminae fuse anteriorly cus blends anteriorly with the median ericothyroid ligament. in the median plane to form the laryngeal prominence The conus elasticus and overlying mucosa close the tracheal (Fig. 8.32A & D). This projection (“Adam's apple") is well inletexcept for the central rima glottidis (opening between marked in men but seldom visible in women. Superior to the vocal folds). this prominence, the laminae diverge to form a V-shaped The epiglottic cartilage, consisting of elastic cartilage, superior thyroid notch. The less distinct inferior thyroid gives flexibility to the epiglottis, a heart-shaped cartilage notch is a shallow indentation in the middle of the inferior covered with mucous membrane (Fig, 8.32B). Situated pos border the cartilage. terior to the root of the tongue and the hyoid and anterior of The posterior border of each lamina projects superiorlyas to the laryngeal inlet, the epiglottic cartilage formsthe the superior horn and inferiorly as the inferior horn. The superior part of the anterior wall and the superior margin of superior border and superior horns attach to the hyoid by the the inlet. Its broad superior end is free. Its tapered inferior thyrohyoid membrane (Fig.8.32A & B). The thick median end, the stalk of the epiglottis, is attached to the angle part of this membrane is the median thyrohyoid ligament; formedby the thyroid laminae by the thyro-epiglottie liga its lateral parts are the lateral thyrohyoid ligaments. ment (Fig. 8.32E). The hyo-epiglottie ligament attaches The inferior horns articulate with the lateral surfaces of the anterior surface of the epiglottic cartilage to the hyoid the cricoid cartilage at the cricothyroid joints (Fig.8.32B). (Fig. 8.33). The quadrangular membrane (Figs. 8.32B The main movements at these joints are rotation and glid and 8.34) is a thin, submucosal sheet of connective tissue ing of the thyroid cartilage, which result in changes in the that extends between the lateral aspects of the arytenoid and length of the vocal folds. The crieoid cartilage is shaped epiglottic cartilages. Its free inferior margin constitutes the like a signet ring with its band facing anteriorly. This ring-like vestibular ligament, which is covered loosely by mucosa to opening of the cartilage fits The posterior an average finger. form the vestibular fold (Fig.8.34). This fold lies superior (signet) part of the cricoid and the anterior is the lamina, to the vocal fold and extends from the thyroid cartilage to the (band) part is the arch (Fig.8.32A). Although much smaller arytenoid cartilage. The free superior margin of the quad than the thyroid cartilage, the cricoid cartilage is thicker and rangular membrane forms the ary-epiglottic ligament, stronger and is the only complete ring of cartilage to encircle which is covered with mucosa to form the ary-epiglottic any part of the airway. It attaches to the inferior margin of fold. The corniculate and cuneiform cartilages appear the thyroid by the median cricothyroid ligament cartilage as small nodules in the posterior part of the ary-epiglottic and to the first trachealring by the cricotracheal ligament. folds. The cormiculate cartilages attach to the apices of the Where the larynx is closest to the skin and most accessible, arytenoid cartilages; the cuneiform cartilages do not directly the median cricothyroid ligament may be felt as a soft spot attach to other The quadrangular membrane and cartilages. during palpation inferior to the thyroid cartilage. conus elasticus are the superior and inferior parts of the sub The arytenoid cartilages are paired, three-sided pyra mucosal fibro-elastic membrane of the larynx. midal cartilages that articulate with the lateral parts of the Interior of Larynx. The laryngeal cavity extends from superior border of the cricoid cartilage lamina (Fig. 8,32B). the laryngeal inlet, through which it communicates with the Each cartilage has an apex superiorly, a vocal process ante laryngopharynx, to the level of the inferior border of the cri riorly, and a large muscular process that projects laterally coid cartilage. Here the laryngeal cavity is continuous with from its base. The apex bears the cormiculate cartilage and the cavity of the trachea (Figs. 8.34 and 8.35A & B). The attaches to the ary-epiglottic fold. The vocal process pro laryngeal cavity includes the: vides the posterior attachment for the vocal ligament, and the muscular process serves as a lever to which the posterior Laryngeal vestibule: between the laryngeal inlet and and lateral crico-arytenoidmuscles are attached. The crico the vestibular folds. arytenoid joints,located between the bases of the arytenoid Middle part of the laryngeal cavity: the central cavity cartilages and the superolateralsurfaces of the lamina of the (airway) between the vestibularand vocal folds. cricoid cartilage (Fig,.32B),permit the arytenoid cartilages Laryngeal ventricle: recesses extending laterally from to slide toward or away from one to another, to tilt anteriorly the middle part of the laryngeal cavity between vestibular and posteriorly, and to rotate. These movements are impor and vocal folds. The laryngeal saccule is a blind pocket tant in approximating, tensing,and relasing the vocal folds. opening into each ventricle that is lined with mucosal The elastic vocal ligaments extend from the junction of glands. the laminae of the thyroid cartilage anteriorly to the vocal Infraglottic cavity: the inferior cavity of the larynx process of the arytenoid cartilage posteriorly (Fig. 8.32E). between the vocal folds and the inferior border the of 1053/117  Chapter 8 Neck 1025 Body of hyoid Vocalis muscle, composed of exceptionally fine muscle Hyo-epiglottic ligament fibers immediately lateral to and terminating at intervals Lesser horn relative to the length of the vocal ligaments (Fig. 8.35A). Median glosso-epiglottic The vocal folds are the sharp-edged folds of mucous mem fold Greater horn brane overlying and incorporating the vocal ligaments and the thyro-arytenoid muscles. They are the source of the Epiglottis sounds (tone) that come from the larynx. These folds pro duce audible vibrations when their free margins are closely (but not tightly) apposed during phonation, and air is forcibly Superior view expired intermittently (Fig. 8,36C). The vocal folds also serve as the main inspiratory sphincter of the larynx when they are FIGURE8.33. Epiglottis and hyo-epiglottic ligament. The epiglottis is a leaf-shaped plate of elastic fibrocartilage, which is covered with mucous tightly closed. Complete adduction of the folds forms an membrane (pink)and is attached anteriorly to the hyoid by the hyo-epiglottic effective sphincter that prevents entry of air. ligament (blue). The epiglottis serves as a diverter valve over the superior The glottis (the vocal apparatus of the larynx) makes up aperture the larynx during swallowing. of the vocal folds and processes, together with the rima glot tidis, the aperture between the vocal folds (Fig.8,35C). The cricoid cartilage, where it is continuous with the lumen of shape of the rima (L. slit) varies according to the position of the trachea. the vocal folds (Fig. 8.36). During ordinary breathing, the rima is narrow and wedge shaped; during forced respiration, The vocal folds control sound production (Figs. 8.35 and it is wide and trapezoidalin shape. The rima glottidis is slit 8.36). The apex of each wedge-shaped fold projects medially like when the vocal folds are closely approximated during into the laryngeal cavity. Each vocal fold contains a: phonation. Variation in the tension and length of the vocal Vocal ligament, consisting of thickened elastic tissue that is the folds, in the width of the rima glottidis, and in the intensity medial free edge theconus elasticus (Figs. 8.32E and 8.34). of the expiratory effort produces changes in the pitch of the of Epiglottic cartilage Epiglottis Left boundary of Ary-epiglottic fold Quadrangular membrane laryngeal inlet Cuneiform tubercle Vestibular ligament Corniculate tubercle Cuneiform cartilage Superior horn of thyroid cartilage -Corniculate cartilage Arytenoid (cut surface) Arytenoid cartilage, medial surface Vestibular fold -Posterior crico-arytenoid ligament Ventricle Vocal process of arytenoid cartilage Vocal fold Vocal ligament Conus Lateral cricothyroid ligament elasticus Lamina of cricoid cartilage Surgical needle spreading halves of cricoid cartilage Mucous membrane Tracheal ring Posterior view FIGURE8.34. Interior of larynx. The posterior wall of the larynx is split in the median plane, and the two sides are spread apart and held in place by a surgical needle. On the left side, the mucous membrane is intact. On the right side, the mucous and submucouscoats are peeled off,and the skeletal coat-consisting of cartilages, ligaments, and the fibro-elastic membrane-isuncovered. 1055/1170  Conus elasticus Lamina of thyroid cartilage Vocal ligament Rima glottidis Arytenoid (B) Forced respiration (D)Whispering cartilage Lamina of cricoid cartilage (A)Normal respiration ("resting" position) (C)Phonation FIGURE 8.36. Variations in shapeof rima glottidis. A. The shape of the rima glottidis, the aperture between the vocal folds, varies according to the posi tion of the vocal folds. During normal respiration, the laryngeal muscles are relaxed and the rima glottidis assumes a narrow, slit-like position. B. During a deep inhalation, the vocal ligaments are abducted by contraction of the posterior crico-arytenoid muscles, opening the rima glottidis widely into an inverted kite shape. C. During phonation, the arytenoid muscles adduct the arytenoid cartilages at the same time that the lateral crico-arytenoid muscles moderately adduct. Air forced between the adducted vocal ligaments produces tone. Stronger contraction the same muscles seals the rima glottidis (Valsalva maneuver). of D. During whispering, the vocal ligaments are strongly adducted by the lateral crico-arytenoid muscles, but the relaxed arytenoid muscles allow air to pass between the arytenoid cartilages (intercartilaginous part of rima glottidis), which is modified into toneless speech. No tone is produced. voice. The lower range of pitch of the voice of postpubertal which pull the muscular processes anteriorly, rotatingthe males results from the greater length of the vocal folds. arytenoid cartilages so that their vocal processes swing The vestibular folds, extending between the thyroid and medially. When this action is combined with that of the the arytenoid cartilages (Figs. 8.34 and 8.35), play little or transverse and oblique arytenoid muscles, which pull no part in voice production; they are protective in function. the arytenoid cartilages together, air pushed through the They consist of two thick folds of mucous membrane enclos rima glottidis causes vibrations of the vocal ligaments ing the vestibular ligaments. The space betweenthese liga ments is the rima vestibuli. The lateral recesses between the vocal and the vestibular folds are the laryngeal ventricles. Internal laryngeal nerve Epiglottis Laryngeal Muscles. The laryngeal muscles are divided (branch of superior into extrinsic and intrinsic groups. Median laryngeal nerve) glosso-epiglottic Extrinsic laryngeal muscles move the larynx as a whole fold (Fig.8.18; Table 8.3). The infrahyoid muscles are depres Thyro-epiglottic Thyro-epiglottic sors of the hyoid and larynx, whereas the suprahyoid muscles Ary-epiglottic (and the stylopharyngeus, a pharyngeal muscle discussed Thyro-arytenoid later in this chapter) are elevators the hyoid and larynx. of Arytenoid Intrinsic laryngeal muscles move the laryngeal com ponents, altering thelength and tension of the vocal folds Crico- Lateral and the size and shape of the rima glottidis (Fig. 8.36). arytenoid Posterior All but one of the intrinsic muscles of the larynx are sup plied by the recurrent laryngeal nerve (Figs. 8.37, 8.39, |Anterior -Cricothyroid and 8.40), a branch CN X. The cricothyroid is of supplied Inferior |branch -Facet by the external laryngeal nerve, one of the two terminal laryngeal for cricoid nerve Posterior branches of the superior laryngeal nerve. branch Facet for cartilage thyroid The actions of the intrinsic laryngeal muscles are easiest to cartilage understand when they are considered as functional groups: Recurrent laryngeal nerve (branch of Tracheal cartilages adductors and abductors, sphincters, and tensors and relax vagus nerve) ers. The intrinsic muscles are illustrated in situ in Figures 8.35D & E and 8.38; their attachments, innervation, and Right lateral view main actions are summarizedin Table 8.5. FIGURE 8.37. Muscles and nerves of larynx and cricothyroid joint. The thyroid cartilage is sawn through to the right of the median plane. Adductors and abductors: These muscles move the vocal The cricothyroid joint is disarticulated, and the right lamina of the thy folds to open and close the rima glottidis. The principal roid cartilage is turned anteriorly (like opening a book), stripping the crico adductors are the lateral crico-arytenoid muscles, thyroid muscles off the arch of the cricoid cartilage. 1057/1170 1028 Chapter Neck 8 Rima glottidis (A) Lateral view (C) Superior view (E) Superior view Cricothyroid Posterior crico-arytenoid Transverse arytenoid Vocalis muscles (B) Superior view (D) Superior view (F) Superior view Thyro-arytenoid Lateral crico-arytenoid Oblique arytenoid FIGURE 8.38. Muscles of the larynx. TABLE 8.5. MUSCLES OF LARYNX Muscle Origin Insertion Innervation Main Action(s) Cricothyroid Anterolateral part of cricoid Inferior margin and External laryngeal nerve Stretches and tenses vocal cartilage