Anatomy_Gray

Anatomy_Gray. Beginning posteriorly these groups (Fig. 8.197) are: occipital nodes near the attachment of the trapezius muscle to the skull and associated with the occipital artery—lymphatic drainage is from the posterior scalp and neck; mastoid nodes (retro-auricular/posterior auricular nodes) posterior to the ear near the attachment of the sternocleidomastoid muscle and associated with the posterior auricular artery—lymphatic drainage is from the posterolateral half of the scalp; pre-auricular and parotid nodes anterior to the ear and associated with the superficial temporal and transverse facial arteries—lymphatic drainage is from the anterior surface of the auricle, the anterolateral scalp, the upper half of the face, the eyelids, and the cheeks; submandibular nodes inferior to the body of the mandible and associated with the facial artery—lymphatic drainage is from structures along the path of the facial artery as high as the forehead, as well as the gingivae, the teeth, and the tongue;


Anatomy_Gray

Anatomy_Gray. mandible and associated with the facial artery—lymphatic drainage is from structures along the path of the facial artery as high as the forehead, as well as the gingivae, the teeth, and the tongue; submental nodes inferior and posterior to the chin—lymphatic drainage is from the center part of the lower lip, the chin, the floor of the mouth, the tip of the tongue, and the lower incisor teeth.


Anatomy_Gray

Anatomy_Gray. Lymphatic flow from these superficial lymph nodes passes in several directions: Drainage from the occipital and mastoid nodes passes to the superficial cervical nodes along the external jugular vein. Drainage from the pre-auricular and parotid nodes, the submandibular nodes, and the submental nodes passes to the deep cervical nodes. The superficial cervical nodes are a collection of lymph nodes along the external jugular vein on the superficial surface of the sternocleidomastoid muscle (Fig. 8.197). They primarily receive lymphatic drainage from the posterior and posterolateral regions of the scalp through the occipital and mastoid nodes, and send lymphatic vessels in the direction of the deep cervical nodes.


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Anatomy_Gray. The deep cervical nodes are a collection of lymph nodes that form a chain along the internal jugular vein (Fig. 8.197). They are divided into upper and lower groups where the intermediate tendon of the omohyoid muscle crosses the common carotid artery and the internal jugular vein. The most superior node in the upper deep cervical group is the jugulodigastric node (Fig. 8.197). This large node is where the posterior belly of the digastric muscle crosses the internal jugular vein and receives lymphatic drainage from the tonsils and tonsillar region. Another large node, usually associated with the lower deep cervical group because it is at or just inferior to the intermediate tendon of the omohyoid muscle, is the jugulo-omohyoid node (Fig. 8.197). This node receives lymphatic drainage from the tongue. The deep cervical nodes eventually receive all lymphatic drainage from the head and neck either directly or through regional groups of nodes.


Anatomy_Gray

Anatomy_Gray. The deep cervical nodes eventually receive all lymphatic drainage from the head and neck either directly or through regional groups of nodes. From the deep cervical nodes, lymphatic vessels form the right and left jugular trunks, which empty into the right lymphatic duct on the right side or the thoracic duct on the left side. The pharynx is a musculofascial half-cylinder that links the oral and nasal cavities in the head to the larynx and esophagus in the neck (Fig. 8.198). The pharyngeal cavity is a common pathway for air and food. The pharynx is attached above to the base of the skull and is continuous below, approximately at the level of vertebra CVI, with the top of the esophagus. The walls of the pharynx are attached anteriorly to the margins of the nasal cavities, oral cavity, and larynx. Based on these anterior relationships the pharynx is subdivided into three regions, the nasopharynx, oropharynx, and laryngopharynx:


Anatomy_Gray

Anatomy_Gray. The posterior apertures (choanae) of the nasal cavities open into the nasopharynx. The posterior opening of the oral cavity (oropharyngeal isthmus) opens into the oropharynx. The superior aperture of the larynx (laryngeal inlet) opens into the laryngopharynx. In addition to these openings, the pharyngeal cavity is related anteriorly to the posterior one-third of the tongue and to the posterior aspect of the larynx. The pharyngotympanic tubes open into the lateral walls of the nasopharynx. Lingual, pharyngeal, and palatine tonsils are on the deep surface of the pharyngeal walls. The pharynx is separated from the posteriorly positioned vertebral column by a thin retropharyngeal space containing loose connective tissue.


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Anatomy_Gray. The pharynx is separated from the posteriorly positioned vertebral column by a thin retropharyngeal space containing loose connective tissue. Although the soft palate is generally considered as part of the roof of the oral cavity, it is also related to the pharynx. The soft palate is attached to the posterior margin of the hard palate and is a type of “flutter valve” that can: swing up (elevate) to close the pharyngeal isthmus, and seal off the nasopharynx from the oropharynx, and swing down (depress) to close the oropharyngeal isthmus and seal off the oral cavity from the oropharynx.


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Anatomy_Gray. The superior and anterior margins of the pharyngeal wall are attached to bone and cartilage, and to ligaments. The two sides of the pharyngeal wall are welded together posteriorly in the midline by a vertically oriented cord-like ligament (the pharyngeal raphe). This connective tissue structure descends from the pharyngeal tubercle on the base of the skull to the level of cervical vertebra CVI where the raphe blends with connective tissue in the posterior wall of the esophagus.


Anatomy_Gray

Anatomy_Gray. There is an irregular C-shaped line of pharyngeal wall attachment on the base of the skull (Fig. 8.200). The open part of the C faces the nasal cavities. Each arm of the C begins at the posterior margin of the medial plate of the pterygoid process of the sphenoid bone, just inferior to the cartilaginous part of the pharyngotympanic tube. The line crosses inferior to the pharyngotympanic tube and then passes onto the petrous part of the temporal bone where it is just medial to the roughening for the attachment of one of the muscles (levator veli palatini) of the soft palate. From here, the line swings medially onto the occipital bone and joins the line from the other side at a prominent elevation of bone in the midline (the pharyngeal tubercle). Anterior vertical line of attachment for the lateral pharyngeal walls


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Anatomy_Gray. Anterior vertical line of attachment for the lateral pharyngeal walls The vertical line of attachment for the lateral pharyngeal walls to structures related to the nasal and oral cavities and larynx is discontinuous and in three parts (Fig. 8.201). On each side, the anterior line of attachment of the lateral pharyngeal wall begins superiorly on the posterior edge of the medial pterygoid plate of the sphenoid bone just inferior to where the pharyngotympanic tube lies against this plate. It continues inferiorly along the edge of the medial plate of the pterygoid process and onto the pterygoid hamulus. From this point, the line descends along the pterygomandibular raphe to the mandible where this part of the line terminates.


Anatomy_Gray

Anatomy_Gray. The pterygomandibular raphe is a linear cord-like connective tissue ligament that spans the distance between the tip of the pterygoid hamulus and a triangular roughening immediately posterior to the third molar on the mandible. It joins a muscle of the lateral pharyngeal wall (superior constrictor) with a muscle of the lateral wall of the oral cavity (buccinator). The second part of the line of attachment of the lateral pharyngeal wall is related to the hyoid bone. It begins on the lower aspect of the stylohyoid ligament, which connects the tip of the styloid process of the temporal bone to the lesser horn of the hyoid bone. The line continues onto the lesser horn and then turns and runs posteriorly along the entire upper surface of the greater horn of the hyoid where it terminates.


Anatomy_Gray

Anatomy_Gray. The most inferior and third part of the line of attachment of the lateral pharyngeal wall begins superiorly on the superior tubercle of the thyroid cartilage, and descends along the oblique line to the inferior tubercle. From the inferior tubercle, the line of attachment continues over the cricothyroid muscle along a tendinous thickening of fascia to the cricoid cartilage where it terminates. The pharyngeal wall is formed by skeletal muscles and by fascia. Gaps between the muscles are reinforced by the fascia and provide routes for structures to pass through the wall. The muscles of the pharynx are organized into two groups based on the orientation of muscle fibers. The constrictor muscles have fibers oriented in a circular direction relative to the pharyngeal wall, whereas the longitudinal muscles have fibers oriented vertically.


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Anatomy_Gray. The constrictor muscles have fibers oriented in a circular direction relative to the pharyngeal wall, whereas the longitudinal muscles have fibers oriented vertically. The three constrictor muscles on each side are major contributors to the structure of the pharyngeal wall (Fig. 8.202 and Table 8.17) and their names indicate their position—superior, middle, and inferior constrictor muscles. Posteriorly, the muscles from each side are joined together by the pharyngeal raphe. Anteriorly, these muscles attach to bones, cartilages, and ligaments related to the lateral margins of the nasal and oral cavities and the larynx. The constrictor muscles overlap each other in a fashion resembling the walls of three flower pots stacked one on the other. The inferior constrictors overlap the lower margins of the middle constrictors and, in the same way, the middle constrictors overlap the superior constrictors. Collectively, the muscles constrict or narrow the pharyngeal cavity.


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Anatomy_Gray. Collectively, the muscles constrict or narrow the pharyngeal cavity. When the constrictor muscles contract sequentially from top to bottom, as in swallowing, they move a bolus of food through the pharynx and into the esophagus. All of the constrictors are innervated by the pharyngeal branch of the vagus nerve [X]. The superior constrictor muscles together bracket the upper part of the pharyngeal cavity (Fig. 8.202). Each muscle is attached anteriorly to the pterygoid hamulus, pterygomandibular raphe, and adjacent bone of the mandible. From these attachments, the muscle fans out posteriorly and joins with its partner muscle from the other side at the pharyngeal raphe. A special band of muscle (the palatopharyngeal sphincter) originates from the anterolateral surface of the soft palate and circles the inner aspect of the pharyngeal wall, blending with the inner aspect of the superior constrictor.


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Anatomy_Gray. When the superior constrictor constricts during swallowing, it forms a prominent ridge on the deep aspect of the pharyngeal wall that catches the margin of the elevated soft palate, which then seals closed the pharyngeal isthmus between the nasopharynx and oropharynx. The middle constrictor muscles are attached to the lower aspect of the stylohyoid ligament, the lesser horn of the hyoid bone, and the entire upper surface of the greater horn of the hyoid (Fig. 8.202). Like the superior constrictors, the middle constrictor muscles fan out posteriorly and attach to the pharyngeal raphe. The posterior part of the middle constrictors overlaps the superior constrictors. The inferior constrictor muscles attach anteriorly to the oblique line of the thyroid cartilage, the cricoid cartilage, and a ligament that spans between these two attachments to cartilage and crosses the cricothyroid muscle (Fig. 8.202).


Anatomy_Gray

Anatomy_Gray. Like the other constrictor muscles, the inferior constrictor muscles spread out posteriorly and attach to the pharyngeal raphe. The posterior part of the inferior constrictors overlaps the middle constrictors. Inferiorly, the muscle fibers blend with and attach into the wall of the esophagus. The parts of the inferior constrictors attached to the cricoid cartilage bracket the narrowest part of the pharyngeal cavity. The three longitudinal muscles of the pharyngeal wall (Fig. 8.203 and Table 8.18) are named according to their origins—stylopharyngeus from the styloid process of the temporal bone, salpingopharyngeus from the cartilaginous part of the pharyngotympanic tube (salpinx is Greek for “tube”), and palatopharyngeus from the soft palate. From their sites of origin, these muscles descend and attach into the pharyngeal wall.


Anatomy_Gray

Anatomy_Gray. The longitudinal muscles elevate the pharyngeal wall, or during swallowing, pull the pharyngeal wall up and over a bolus of food being moved through the pharynx and into the esophagus. The cylindrical stylopharyngeus muscle (Fig. 8.203A) originates from the base of the medial surface of the styloid process of the temporal bone and descends between the superior and middle constrictor muscles to fan out on, and blend with, the deep surface of the pharyngeal wall. It is innervated by the glossopharyngeal nerve [IX]. The salpingopharyngeus (Fig. 8.203B) is a small muscle originating from the inferior aspect of the pharyngotympanic tube, descending on, and blending into, the deep surface of the pharyngeal wall. It is innervated by the vagus nerve [X].


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Anatomy_Gray. The palatopharyngeus (Fig. 8.203B), in addition to being a muscle of the pharynx, is also a muscle of the soft palate (see pp. 1098–1099). It is attached to the upper surface of the palatine aponeurosis, and passes posteriorly and inferiorly to blend with the deep surface of the pharyngeal wall. The palatopharyngeus forms an important fold in the overlying mucosa (the palatopharyngeal arch). This arch is visible through the oral cavity and is a landmark for finding the palatine tonsil, which is immediately anterior to it on the oropharyngeal wall. In addition to elevating the pharynx, the palatopharyngeus participates in closing the oropharyngeal isthmus by depressing the palate and moving the palatopharyngeal fold toward the midline. The palatopharyngeus is innervated by the vagus nerve [X]. The pharyngeal fascia is separated into two layers, which sandwich the pharyngeal muscles between them:


Anatomy_Gray

Anatomy_Gray. The palatopharyngeus is innervated by the vagus nerve [X]. The pharyngeal fascia is separated into two layers, which sandwich the pharyngeal muscles between them: A thin layer (buccopharyngeal fascia) coats the outside of the muscular part of the wall and is a component of the pretracheal layer of cervical fascia (see p. 991). A much thicker layer (pharyngobasilar fascia) lines the inner surface. The fascia reinforces the pharyngeal wall where muscle is deficient. This is particularly evident above the level of the superior constrictor where the pharyngeal wall is formed almost entirely of fascia (Fig. 8.203). This part of the wall is reinforced externally by muscles of the soft palate (tensor and levator veli palatini). Gaps in the pharyngeal wall and structures passing through them Gaps between muscles of the pharyngeal wall provide important routes for muscles and neurovascular tissues (Fig. 8.204).


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Anatomy_Gray. Gaps in the pharyngeal wall and structures passing through them Gaps between muscles of the pharyngeal wall provide important routes for muscles and neurovascular tissues (Fig. 8.204). Above the margin of the superior constrictor, the pharyngeal wall is deficient in muscle and completed by pharyngeal fascia. The tensor and levator veli palatini muscles of the soft palate initially descend from the base of the skull and are lateral to the pharyngeal fascia. In this position, they reinforce the pharyngeal wall: The levator veli palatini passes through the pharyngeal fascia inferior to the pharyngotympanic tube and enters the soft palate. The tendon of the tensor veli palatini turns medially around the pterygoid hamulus and passes through the origin of the buccinator muscle to enter the soft palate.


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Anatomy_Gray. The tendon of the tensor veli palatini turns medially around the pterygoid hamulus and passes through the origin of the buccinator muscle to enter the soft palate. One of the largest and most important apertures in the pharyngeal wall is between the superior and middle constrictor muscles of the pharynx and the posterior border of the mylohyoid muscle, which forms the floor of the mouth (Fig. 8.204). This triangular-shaped gap (oropharyngeal triangle) not only enables the stylopharyngeus to slip into the pharyngeal wall, but also allows muscles, nerves, and vessels to pass between regions lateral to the pharyngeal wall and the oral cavity, particularly to the tongue. The gap between the middle and inferior constrictor muscles allows the internal laryngeal vessels and nerve access to the aperture in the thyrohyoid membrane to enter the larynx.


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Anatomy_Gray. The gap between the middle and inferior constrictor muscles allows the internal laryngeal vessels and nerve access to the aperture in the thyrohyoid membrane to enter the larynx. The recurrent laryngeal nerves and accompanying inferior laryngeal vessels enter the larynx posterior to the inferior horn of the thyroid cartilage deep to the inferior margin of the inferior constrictor muscle. The nasopharynx is behind the posterior apertures (choanae) of the nasal cavities and above the level of the soft palate (Fig. 8.205). Its ceiling is formed by the sloping base of the skull and consists of the posterior part of the body of the sphenoid bone and the basal part of the occipital bone. The ceiling and lateral walls of the nasopharynx form a domed vault at the top of the pharyngeal cavity that is always open.


Anatomy_Gray

Anatomy_Gray. The cavity of the nasopharynx is continuous below with the cavity of the oropharynx at the pharyngeal isthmus. The position of the pharyngeal isthmus is marked on the pharyngeal wall by a mucosal fold caused by the underlying palatopharyngeal sphincter, which is part of the superior constrictor muscle. Elevation of the soft palate and constriction of the palatopharyngeal sphincter closes the pharyngeal isthmus during swallowing and separates the nasopharynx from the oropharynx. There is a large collection of lymphoid tissue (the pharyngeal tonsil) in the mucosa covering the roof of the nasopharynx. Enlargement of this tonsil, known then as adenoids, can occlude the nasopharynx so that breathing is only possible through the oral cavity (Fig. 8.205A). The most prominent features on each lateral wall of the nasopharynx are: the pharyngeal opening of the pharyngotympanic tube, and mucosal elevations and folds covering the end of the pharyngotympanic tube and the adjacent muscles.


Anatomy_Gray

Anatomy_Gray. The opening of the pharyngotympanic tube is posterior to and slightly above the level of the hard palate, and lateral to the top of the soft palate (Fig. 8.205A). Because the pharyngotympanic tube projects into the nasopharynx from a posterolateral direction, its posterior rim forms an elevation or bulge on the pharyngeal wall. Posterior to this tubal elevation (torus tubarius) is a deep recess (pharyngeal recess) (Fig. 8.205A). Mucosal folds related to the pharyngotympanic tube include: the small vertical salpingopharyngeal fold, which descends from the tubal elevation and overlies the salpingopharyngeus muscle, and a broad fold or elevation (torus levatorius) that appears to emerge from just under the opening of the pharyngotympanic tube, continues medially onto the upper surface of the soft palate, and overlies the levator veli palatini muscle.


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Anatomy_Gray. The oropharynx is posterior to the oral cavity, inferior to the level of the soft palate, and superior to the upper margin of the epiglottis (Fig. 8.205). The palatoglossal folds (arches), one on each side, that cover the palatoglossal muscles, mark the boundary between the oral cavity and the oropharynx. The arched opening between the two folds is the oropharyngeal isthmus. Just posterior and medial to these folds are another pair of folds (arches), the palatopharyngeal folds, one on each side, that overlie the palatopharyngeus muscles.


Anatomy_Gray

Anatomy_Gray. The anterior wall of the oropharynx inferior to the oropharyngeal isthmus is formed by the upper part of the posterior one-third or pharyngeal part of the tongue. Large collections of lymphoid tissue (the lingual tonsils) are in the mucosa covering this part of the tongue. A pair of mucosal pouches (valleculae), one on each side of the midline, between the base of the tongue and epiglottis, are depressions formed between a midline mucosal fold and two lateral folds that connect the tongue to the epiglottis. The palatine tonsils are on the lateral walls of the oropharynx. On each side, there is a large ovoid collection of lymphoid tissue in the mucosa lining the superior constrictor muscle and between the palatoglossal and palatopharyngeal arches. The palatine tonsils are visible through the oral cavity just posterior to the palatoglossal folds.


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Anatomy_Gray. When holding liquid or solids in the oral cavity, the oropharyngeal isthmus is closed by depression of the soft palate, elevation of the back of the tongue, and movement toward the midline of the palatoglossal and palatopharyngeal folds. This allows a person to breathe while chewing or manipulating material in the oral cavity. On swallowing, the oropharyngeal isthmus is opened, the palate is elevated, the laryngeal cavity is closed, and the food or liquid is directed into the esophagus. A person cannot breathe and swallow at the same time because the airway is closed at two sites, the pharyngeal isthmus and the larynx. The laryngopharynx extends from the superior margin of the epiglottis to the top of the esophagus at the level of vertebra CVI (Fig. 8.205). The laryngeal inlet opens into the anterior wall of the laryngopharynx. Inferior to the laryngeal inlet, the anterior wall consists of the posterior aspect of the larynx.


Anatomy_Gray

Anatomy_Gray. The laryngeal inlet opens into the anterior wall of the laryngopharynx. Inferior to the laryngeal inlet, the anterior wall consists of the posterior aspect of the larynx. There is another pair of mucosal recesses (piriform fossae) between the central part of the larynx and the more lateral lamina of the thyroid cartilage. The piriform fossae form channels that direct solids and liquids from the oral cavity around the raised laryngeal inlet and into the esophagus. Collections of lymphoid tissue in the mucosa of the pharynx surrounding the openings of the nasal and oral cavities (Waldeyer’s tonsillar ring) are part of the body’s defense system. The largest of these collections form distinct masses (tonsils). Tonsils occur mainly in three areas (Fig. 8.205): The pharyngeal tonsil, known as adenoids when enlarged, is in the midline on the roof of the nasopharynx.


Anatomy_Gray

Anatomy_Gray. The pharyngeal tonsil, known as adenoids when enlarged, is in the midline on the roof of the nasopharynx. The palatine tonsils are on each side of the oropharynx between the palatoglossal and palatopharyngeal arches just posterior to the oropharyngeal isthmus. (The palatine tonsils are visible through the open mouth of a patient when the tongue is depressed.) The lingual tonsils refer collectively to numerous lymphoid nodules on the posterior one-third of the tongue. Small lymphoid nodules also occur in the pharyngotympanic tube near its opening into the nasopharynx, and on the upper surface of the soft palate. Numerous vessels supply the pharyngeal wall (Fig. 8.206). Arteries that supply upper parts of the pharynx include: the ascending pharyngeal artery, the ascending palatine and tonsillar branches of the facial artery, and numerous branches of the maxillary and the lingual arteries. All these vessels are from the external carotid artery.


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Anatomy_Gray. All these vessels are from the external carotid artery. Arteries that supply the lower parts of the pharynx include pharyngeal branches from the inferior thyroid artery, which originates from the thyrocervical trunk of the subclavian artery. The major blood supply to the palatine tonsil is from the tonsillar branch of the facial artery, which penetrates the superior constrictor muscle. Veins of the pharynx form a plexus, which drains superiorly into the pterygoid plexus in the infratemporal fossa, and inferiorly into the facial and internal jugular veins (Fig. 8.207). Lymphatic vessels from the pharynx drain into the deep cervical nodes and include retropharyngeal (between the nasopharynx and vertebral column), paratracheal, and infrahyoid nodes (Fig. 8.207). The palatine tonsils drain through the pharyngeal wall into the jugulodigastric nodes in the region where the facial vein drains into the internal jugular vein (and inferior to the posterior belly of the digastric muscle).


Anatomy_Gray

Anatomy_Gray. Motor and most sensory innervation (except for the nasal region) of the pharynx is mainly through branches of the vagus [X] and glossopharyngeal [IX] nerves, which form a plexus in the outer fascia of the pharyngeal wall (Fig. 8.208A). The pharyngeal plexus is formed by: the pharyngeal branch of the vagus nerve [X], branches from the external laryngeal nerve from the superior laryngeal branch of the vagus nerve [X], and pharyngeal branches of the glossopharyngeal nerve [IX]. The pharyngeal branch of the vagus nerve [X] originates from the upper part of its inferior ganglion above the origin of the superior laryngeal nerve and is the major motor nerve of the pharynx. All muscles of the pharynx are innervated by the vagus nerve [X] mainly through the pharyngeal plexus, except for the stylopharyngeus, which is innervated directly by a branch of the glossopharyngeal nerve [IX] (Fig. 8.208B). Each subdivision of the pharynx has a different sensory innervation:


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Anatomy_Gray. Each subdivision of the pharynx has a different sensory innervation: The nasopharynx is innervated by a pharyngeal branch of the maxillary nerve [V2] that originates in the pterygopalatine fossa and passes through the palatovaginal canal in the sphenoid bone to reach the roof of the pharynx. The oropharynx is innervated by the glossopharyngeal nerve [IX] via the pharyngeal plexus. The laryngopharynx is innervated by the vagus nerve [X] via the internal branch of the superior laryngeal nerve. The glossopharyngeal nerve [IX] is related to the pharynx throughout most of its course outside the cranial cavity.


Anatomy_Gray

Anatomy_Gray. The glossopharyngeal nerve [IX] is related to the pharynx throughout most of its course outside the cranial cavity. After exiting the skull through the jugular foramen, the glossopharyngeal nerve [IX] descends on the posterior surface of the stylopharyngeus muscle (Fig. 8.208B), passes onto the lateral surface of the stylopharyngeus, and then passes anteriorly through the gap (oropharyngeal triangle) between the superior constrictor, middle constrictor, and mylohyoid muscles to eventually reach the posterior aspect of the tongue. As the glossopharyngeal nerve [IX] passes under the free edge of the superior constrictor, it is just inferior to the palatine tonsil lying on the deep surface of the superior constrictor.


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Anatomy_Gray. As the glossopharyngeal nerve [IX] passes under the free edge of the superior constrictor, it is just inferior to the palatine tonsil lying on the deep surface of the superior constrictor. Pharyngeal branches to the pharyngeal plexus and a motor branch to the stylopharyngeus muscle are among branches that originate from the glossopharyngeal nerve [IX] in the neck. Because sensory innervation of the oropharynx is by the glossopharyngeal nerve [IX], this nerve carries sensory innervation from the palatine tonsil and is also the afferent limb of the gag reflex (see “In the clinic” on p. 889). The larynx is a hollow musculoligamentous structure with a cartilaginous framework that caps the lower respiratory tract. The cavity of the larynx is continuous below with the trachea, and above opens into the pharynx immediately posterior and slightly inferior to the tongue and the posterior opening (oropharyngeal isthmus) of the oral cavity (Fig. 8.209A,B).


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Anatomy_Gray. The larynx is both a valve (or sphincter) to close the lower respiratory tract, and an instrument to produce sound. It is composed of: three large unpaired cartilages (cricoid, thyroid, and epiglottis), three pairs of smaller cartilages (arytenoid, corniculate, and cuneiform), and a fibro-elastic membrane and numerous intrinsic muscles. The larynx is suspended from the hyoid bone above and attached to the trachea below by membranes and ligaments. It is highly mobile in the neck and can be moved up and down and forward and backward by the action of extrinsic muscles that attach either to the larynx itself or to the hyoid bone. During swallowing, the dramatic upward and forward movements of the larynx facilitate closing the laryngeal inlet and opening the esophagus. Motor and sensory innervation of the larynx is provided by the vagus nerve [X].


Anatomy_Gray

Anatomy_Gray. Motor and sensory innervation of the larynx is provided by the vagus nerve [X]. The cricoid cartilage is the most inferior of the laryngeal cartilages and completely encircles the airway (Fig. 8.210). It is shaped like a signet ring with a broad lamina of cricoid cartilage posterior to the airway and a much narrower arch of cricoid cartilage circling anteriorly. The posterior surface of the lamina is characterized by two shallow oval depressions separated by a vertical ridge. The esophagus is attached to the ridge and the depressions are for attachment of the posterior crico-arytenoid muscles. The cricoid cartilage has two articular facets on each side for articulation with other laryngeal cartilages: One facet is on the sloping superolateral surface of the lamina and articulates with the base of an arytenoid cartilage.


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Anatomy_Gray. One facet is on the sloping superolateral surface of the lamina and articulates with the base of an arytenoid cartilage. The other facet is on the lateral surface of the lamina near its base and is for articulation with the medial surface of the inferior horn of the thyroid cartilage. The thyroid cartilage (Fig. 8.211) is the largest of the laryngeal cartilages. It is formed by a right and a left lamina, which are widely separated posteriorly, but converge and join anteriorly. The most superior point of the site of fusion between the two broad flat laminae projects forward as the laryngeal prominence (Adam’s apple). The angle between the two laminae is more acute in men (90°) than in women (120°) so the laryngeal prominence is more apparent in men than women.


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Anatomy_Gray. Just superior to the laryngeal prominence, the superior thyroid notch separates the two laminae as they diverge laterally. Both the superior thyroid notch and the laryngeal prominence are palpable landmarks in the neck. There is a less distinct inferior thyroid notch in the midline along the base of the thyroid cartilage. The posterior margin of each lamina of the thyroid cartilage is elongated to form a superior horn and an inferior horn: The medial surface of the inferior horn has a facet for articulation with the cricoid cartilage. The superior horn is connected by a lateral thyrohyoid ligament to the posterior end of the greater horn of the hyoid bone. The lateral surface of each thyroid lamina is marked by a ridge (the oblique line), which curves anteriorly from the base of the superior horn to a little short of midway along the inferior margin of the lamina.


Anatomy_Gray

Anatomy_Gray. The ends of the oblique line are expanded to form superior and inferior thyroid tubercles. The oblique line is a site of attachment for the extrinsic muscles of the larynx (sternothyroid, thyrohyoid, and inferior constrictor). The epiglottis is a leaf-shaped cartilage attached by its stem to the posterior aspect of the thyroid cartilage at the angle (Fig. 8.212) and projects posterosuperiorly from its attachment to the thyroid cartilage. The attachment is via the thyro-epiglottic ligament in the midline approximately midway between the laryngeal prominence and the inferior thyroid notch. The upper margin of the epiglottis is behind the pharyngeal part of the tongue. The inferior half of the posterior surface of the epiglottis is raised slightly to form an epiglottic tubercle. The two arytenoid cartilages are pyramid-shaped cartilages with three surfaces, a base of arytenoid cartilage and an apex of arytenoid cartilage (Fig. 8.213):


Anatomy_Gray

Anatomy_Gray. The two arytenoid cartilages are pyramid-shaped cartilages with three surfaces, a base of arytenoid cartilage and an apex of arytenoid cartilage (Fig. 8.213): The base is concave and articulates with the sloping articular facet on the superolateral surface of the lamina of cricoid cartilage. The apex articulates with a corniculate cartilage. The medial surface of each cartilage faces the other. The anterolateral surface has two depressions, separated by a ridge, for muscle (vocalis) and ligament (vestibular ligament) attachment. The posterior surface is covered by the transverse arytenoid muscle (see Fig. 8.223). The anterior angle of the base is elongated into a vocal process to which the vocal ligament is attached. The lateral angle is similarly elongated into a muscular process for attachment of the posterior and lateral crico-arytenoid muscles.


Anatomy_Gray

Anatomy_Gray. The corniculate cartilages (Fig. 8.214) are two small conical cartilages whose bases articulate with the apices of the arytenoid cartilages. Their apices project posteromedially toward each other. These two small club-shaped cartilages (Fig. 8.214) lie anterior to the corniculate cartilages and are suspended in the part of the fibro-elastic membrane of the larynx that attaches the arytenoid cartilages to the lateral margin of the epiglottis. The thyrohyoid membrane is a tough fibro-elastic ligament that spans between the superior margin of the thyroid cartilage below and the hyoid bone above (Fig. 8.215). It is attached to the superior margin of the thyroid laminae and adjacent anterior margins of the superior horns, and ascends medial to the greater horns and posterior to the body of the hyoid bone to attach to the superior margins of these structures.


Anatomy_Gray

Anatomy_Gray. An aperture in the lateral part of the thyrohyoid membrane on each side is for the superior laryngeal artery, the internal branch of the superior laryngeal nerve, and lymphatics. The posterior borders of the thyrohyoid membrane are thickened to form the lateral thyrohyoid ligaments. The membrane is also thickened anteriorly in the midline to form the median thyrohyoid ligament. Occasionally, there is a small cartilage (triticeal cartilage) in each lateral thyrohyoid ligament. The hyo-epiglottic ligament (Fig. 8.215) extends from the midline of the epiglottis, anterosuperiorly to the body of the hyoid bone. The cricotracheal ligament (Fig. 8.215) runs from the lower border of the cricoid cartilage to the adjacent upper border of the first tracheal cartilage. Fibro-elastic membrane of the larynx


Anatomy_Gray

Anatomy_Gray. The cricotracheal ligament (Fig. 8.215) runs from the lower border of the cricoid cartilage to the adjacent upper border of the first tracheal cartilage. Fibro-elastic membrane of the larynx The fibro-elastic membrane of the larynx links together the laryngeal cartilages and completes the architectural framework of the laryngeal cavity. It is composed of two parts—a lower conus elasticus and an upper quadrangular membrane. The conus elasticus (Fig. 8.216) is attached to the arch of cricoid cartilage and extends superiorly to end in a free upper margin within the space enclosed by the thyroid cartilage. On each side, this upper free margin attaches: anteriorly to the thyroid cartilage, and posteriorly to the vocal processes of the arytenoid cartilages. The free margin between these two points of attachment is thickened to form the vocal ligament, which is under the vocal fold (true vocal cord) of the larynx.


Anatomy_Gray

Anatomy_Gray. The free margin between these two points of attachment is thickened to form the vocal ligament, which is under the vocal fold (true vocal cord) of the larynx. The conus elasticus is also thickened anteriorly in the midline to form a distinct median cricothyroid ligament, which spans the distance between the arch of cricoid cartilage and the inferior thyroid notch and adjacent deep surface of the thyroid cartilage up to the attachment of the vocal ligaments. In emergency situations, when the airway is blocked above the level of the vocal folds, the median cricothyroid ligament can be perforated to establish an airway. Except for small vessels and the occasional presence of a pyramidal lobe of the thyroid gland, normally there are few structures between the median cricothyroid ligament and skin.


Anatomy_Gray

Anatomy_Gray. The quadrangular membrane on each side runs between the lateral margin of the epiglottis and the anterolateral surface of the arytenoid cartilage on the same side (Fig. 8.217). It is also attached to the corniculate cartilage, which articulates with the apex of arytenoid cartilage. Each quadrangular membrane has a free upper margin, between the top of the epiglottis and the corniculate cartilage, and a free lower margin. The free lower margin is thickened to form the vestibular ligament under the vestibular fold (false vocal cord) of the larynx. The vestibular ligament is attached posteriorly to the superior depression on the anterolateral surface of the arytenoid cartilage and anteriorly to the thyroid angle just superior to the attachment of the vocal ligament.


Anatomy_Gray

Anatomy_Gray. On each side, the vestibular ligament of the quadrangular membrane is separated from the vocal ligament of the cricothyroid ligament below by a gap. Because the vestibular ligament attaches to the anterolateral surface of the arytenoid cartilage and the vocal ligament attaches to the vocal process of the same cartilage, the vestibular ligament is lateral to the vocal ligament when viewed from above (Fig. 8.218). The joints between the inferior horns of the thyroid cartilage and the cricoid cartilage, and between the cricoid cartilage and arytenoid cartilages are synovial. Each is surrounded by a capsule and is reinforced by associated ligaments. The cricothyroid joints enable the thyroid cartilage to move forward and tilt downward on the cricoid cartilage (Fig. 8.219).


Anatomy_Gray

Anatomy_Gray. Because the vocal ligaments pass between the posterior aspect of the thyroid angle and the arytenoid cartilages that sit on the lamina of cricoid cartilage, forward movement and downward rotation of the thyroid cartilage on the cricoid cartilage effectively lengthens and puts tension on the vocal ligaments. The crico-arytenoid joints between articular facets on the superolateral surfaces of the cricoid cartilage and the bases of the arytenoid cartilages enable the arytenoid cartilages to slide away or toward each other and to rotate so that the vocal processes pivot either toward or away from the midline. These movements abduct and adduct the vocal ligaments (Fig. 8.220). Cavity of the larynx The central cavity of the larynx (Fig. 8.221) is tubular and lined by mucosa. Its architectural support is provided by the fibro-elastic membrane of the larynx and by the laryngeal cartilages to which it is attached.


Anatomy_Gray

Anatomy_Gray. The superior aperture of the cavity (laryngeal inlet) opens into the anterior aspect of the pharynx just below and posterior to the tongue (Fig. 8.221A): Its anterior border is formed by mucosa covering the superior margin of the epiglottis. Its lateral borders are formed by mucosal folds (ary-epiglottic folds), which enclose the superior margins of the quadrangular membranes and adjacent soft tissues, and two tubercles on the more posterolateral margin of the laryngeal inlet on each side mark the positions of the underlying cuneiform and corniculate cartilages. Its posterior border in the midline is formed by a mucosal fold that forms a depression (interarytenoid notch) between the two corniculate tubercles.


Anatomy_Gray

Anatomy_Gray. Its posterior border in the midline is formed by a mucosal fold that forms a depression (interarytenoid notch) between the two corniculate tubercles. The inferior opening of the laryngeal cavity is continuous with the lumen of the trachea, is completely encircled by the cricoid cartilage, and is horizontal in position unlike the laryngeal inlet, which is oblique and points posterosuperiorly into the pharynx. In addition, the inferior opening is continuously open, whereas the laryngeal inlet can be closed by downward movement of the epiglottis. Two pairs of mucosal folds, the vestibular and vocal folds, which project medially from the lateral walls of the laryngeal cavity, constrict it and divide it into three major regions—the vestibule, a middle chamber, and the infraglottic cavity (Fig. 8.221B): The vestibule is the upper chamber of the laryngeal cavity between the laryngeal inlet and the vestibular folds, which encloses the vestibular ligaments and associated soft tissues.


Anatomy_Gray

Anatomy_Gray. The vestibule is the upper chamber of the laryngeal cavity between the laryngeal inlet and the vestibular folds, which encloses the vestibular ligaments and associated soft tissues. The middle part of the laryngeal cavity is very thin and is between the vestibular folds above and the vocal folds below. The infraglottic space is the most inferior chamber of the laryngeal cavity and is between the vocal folds (which encloses the vocal ligaments and related soft tissues) and the inferior opening of the larynx.


Anatomy_Gray

Anatomy_Gray. On each side, the mucosa of the middle cavity bulges laterally through the gap between the vestibular and vocal ligaments to produce an expanded trough-shaped space (a laryngeal ventricle) (Fig. 8.221A). An elongate tubular extension of each ventricle (laryngeal saccule) projects anterosuperiorly between the vestibular fold and thyroid cartilage and may reach as high as the top of the thyroid cartilage. Within the walls of these laryngeal saccules are numerous mucous glands. Mucus secreted into the saccules lubricates the vocal folds. When viewed from above (Fig. 8.221C,D), there is a triangular opening (the rima vestibuli) between the two adjacent vestibular folds at the entrance to the middle chamber of the laryngeal cavity. The apex of the opening is anterior and its base is formed by the posterior wall of the laryngeal cavity.


Anatomy_Gray

Anatomy_Gray. Inferior to the vestibular folds, the vocal folds (true vocal cords) and adjacent mucosa-covered parts of the arytenoid cartilages form the lateral walls of a similar, but narrower, triangular opening (the rima glottidis between the two adjacent vocal folds). This opening separates the middle chamber above from the infraglottic cavity below. The base of this triangular opening is formed by the fold of mucosa (interarytenoid fold) at the bottom of the interarytenoid notch. Both the rima glottidis and the rima vestibuli can be opened and closed by movement of the arytenoid cartilages and associated fibro-elastic membranes.


Anatomy_Gray

Anatomy_Gray. Both the rima glottidis and the rima vestibuli can be opened and closed by movement of the arytenoid cartilages and associated fibro-elastic membranes. The intrinsic muscles of the larynx (Table 8.19) adjust tension in the vocal ligaments, open and close the rima glottidis, control the inner dimensions of the vestibule, close the rima vestibuli, and facilitate closing of the laryngeal inlet. They do this mainly by: acting on the cricothyroid and crico-arytenoid joints, adjusting the distance between the epiglottis and arytenoid cartilages, pulling directly on the vocal ligaments, and forcing soft tissues associated with the quadrangular membranes and vestibular ligaments toward the midline. The fan-shaped cricothyroid muscles are attached to the anterolateral surfaces of the arch of the cricoid cartilage and expand superiorly and posteriorly to attach to the thyroid cartilage (Fig. 8.222). Each muscle has an oblique part and a straight part:


Anatomy_Gray

Anatomy_Gray. Each muscle has an oblique part and a straight part: The oblique part runs in a posterior direction from the arch of the cricoid cartilage to the inferior horn of the thyroid cartilage. The straight part runs more vertically from the arch of the cricoid cartilage to the posteroinferior margin of the thyroid lamina. The cricothyroid muscles move the cricothyroid joints. They pull the thyroid cartilage forward and rotate it down relative to the cricoid cartilage. These actions lengthen the vocal folds. The cricothyroid muscles are the only intrinsic muscles of the larynx innervated by the superior laryngeal branches of the vagus nerves [X]. All other intrinsic muscles are innervated by the recurrent laryngeal branches of the vagus nerves [X].


Anatomy_Gray

Anatomy_Gray. There is a right and a left posterior crico-arytenoid muscle (Fig. 8.223). The fibers of each muscle originate from a large shallow depression on the posterior surface of the lamina of the cricoid cartilage, and run superiorly and laterally to converge on the muscular processes of the arytenoid cartilage. The posterior crico-arytenoid muscles abduct and externally (laterally) rotate the arytenoid cartilages, thereby opening the rima glottidis. These muscles are the primary abductors of the vocal folds. They are innervated by the recurrent laryngeal branches of the vagus nerves [X]. The lateral crico-arytenoid muscle on each side originates from the upper surface of the arch of the cricoid cartilage, and runs posteriorly and superiorly to insert on the muscular process of the arytenoid cartilage (Fig. 8.223). The lateral crico-arytenoid muscles internally rotate the arytenoid cartilages. These movements result in adducted (closed) vocal folds.


Anatomy_Gray

Anatomy_Gray. The lateral crico-arytenoid muscles internally rotate the arytenoid cartilages. These movements result in adducted (closed) vocal folds. The lateral crico-arytenoids are innervated by the recurrent laryngeal branches of the vagus nerves [X]. The single transverse arytenoid muscle spans the distance between adjacent lateral margins of the arytenoid cartilages and covers the posterior surfaces of these cartilages (Fig. 8.223). It adducts the arytenoid cartilages and is innervated by the recurrent laryngeal branches of the vagus nerves [X]. Each of the two oblique arytenoid muscles runs from the posterior surface of the muscular process of one arytenoid cartilage to the apex of the arytenoid cartilage on the other side (Fig. 8.223). Some fibers of the muscle continue laterally around the margin of the arytenoid cartilage and into the ary-epiglottic fold where they continue as the ary-epiglottic part of the muscle (Fig. 8.224).


Anatomy_Gray

Anatomy_Gray. The oblique arytenoids can narrow the laryngeal inlet by constricting the distance between the arytenoid cartilages and the epiglottis. They are innervated by the recurrent laryngeal branches of the vagus nerves [X]. The vocalis muscles are elongate muscles lateral to and running parallel with each vocal ligament (Fig. 8.223). The fibers in each muscle are attached posteriorly to the lateral surface of the vocal process and adjacent depression on the anterolateral surface of the arytenoid cartilage, and anteriorly insert along the length of the vocal ligament to the thyroid angle. The vocalis muscles adjust tension in the vocal folds and are innervated by the recurrent laryngeal branches of the vagus nerves [X].


Anatomy_Gray

Anatomy_Gray. The vocalis muscles adjust tension in the vocal folds and are innervated by the recurrent laryngeal branches of the vagus nerves [X]. The two thyro-arytenoid muscles are broad flat muscles lateral to the fibro-elastic membrane of the larynx and the laryngeal ventricles and saccules (Fig. 8.224). Each muscle runs from a vertical line of origin on the lower half of the thyroid angle and adjacent external surface of the cricothyroid ligament to the anterolateral surface of the arytenoid cartilage. Some of the fibers may continue into the ary-epiglottic fold and reach the margin of the epiglottis. These fibers are the thyro-epiglottic part of the muscle.


Anatomy_Gray

Anatomy_Gray. Because the thyro-arytenoid muscles are broad and lateral to the quadrangular membrane, they act as a sphincter of the vestibule by pushing soft tissues medial to the muscles toward the midline. The muscles also narrow the laryngeal inlet by pulling the arytenoid cartilages forward while simultaneously pulling the epiglottis toward the arytenoid cartilages. The thyro-arytenoid muscles are innervated by the recurrent laryngeal branches of the vagus nerves [X]. Function of the larynx The larynx is an elaborate sphincter for the lower respiratory tract and provides a mechanism for producing sounds. Adjustments of the size of the central cavity of the larynx result from changes in the dimensions of the rima glottidis, the rima vestibuli, the vestibule, and the laryngeal inlet (Fig. 8.225). These changes result from muscle actions and laryngeal mechanics.


Anatomy_Gray

Anatomy_Gray. During quiet respiration, the laryngeal inlet, vestibule, rima vestibuli, and rima glottidis are open. The arytenoid cartilages are abducted and the rima glottidis is triangular shaped (Fig. 8.225A). During forced inspiration (Fig. 8.225B), the arytenoid cartilages are rotated laterally, mainly by the action of the posterior crico-arytenoid muscles. As a result, the vocal folds are abducted and the rima glottidis widens into a rhomboid shape, which effectively increases the diameter of the laryngeal airway. When phonating, the arytenoid cartilages and vocal folds are adducted and air is forced through the closed rima glottidis (Fig. 8.225C). This action causes the vocal folds to vibrate against each other and produce sounds, which can then be modified by the upper parts of the airway and oral cavity. Tension in the vocal folds can be adjusted by the vocalis and cricothyroid muscles.


Anatomy_Gray

Anatomy_Gray. Effort closure of the larynx (Fig. 8.225D) occurs when air is retained in the thoracic cavity to stabilize the trunk, for example during heavy lifting, or as part of the mechanism for increasing intra-abdominal pressure. During effort closure, the rima glottidis is completely closed, as is the rima vestibuli and lower parts of the vestibule. The result is to completely and forcefully shut the airway.


Anatomy_Gray

Anatomy_Gray. During swallowing, the rima glottidis, rima vestibuli, and vestibule are closed and the laryngeal inlet is narrowed. In addition, the larynx moves up and forward. This action causes the epiglottis to swing downward toward the arytenoid cartilages and to effectively narrow or close the laryngeal inlet (Fig. 8.225E). The up and forward movement of the larynx also opens the esophagus, which is attached to the posterior aspect of the lamina of the cricoid cartilage. All these actions together prevent solids and liquids from entry into the airway and facilitate their movement through the piriform fossae into the esophagus. The major blood supply to the larynx is by the superior and inferior laryngeal arteries (Fig. 8.226):


Anatomy_Gray

Anatomy_Gray. The major blood supply to the larynx is by the superior and inferior laryngeal arteries (Fig. 8.226): The superior laryngeal artery originates near the upper margin of the thyroid cartilage from the superior thyroid branch of the external carotid artery, and accompanies the internal branch of the superior laryngeal nerve through the thyrohyoid membrane to reach the larynx. The inferior laryngeal artery originates from the inferior thyroid branch of the thyrocervical trunk of the subclavian artery low in the neck and, together with the recurrent laryngeal nerve, ascends in the groove between the esophagus and trachea—it enters the larynx by passing deep to the margin of the inferior constrictor muscle of the pharynx. Veins draining the larynx accompany the arteries: Superior laryngeal veins drain into superior thyroid veins, which in turn drain into the internal jugular veins (Fig. 8.227).


Anatomy_Gray

Anatomy_Gray. Veins draining the larynx accompany the arteries: Superior laryngeal veins drain into superior thyroid veins, which in turn drain into the internal jugular veins (Fig. 8.227). Inferior laryngeal veins drain into inferior thyroid veins, which drain into the left brachiocephalic vein. Lymphatics drain regions above and below the vocal folds: Those above the vocal folds follow the superior laryngeal artery and terminate in deep cervical nodes associated with the bifurcation of the common carotid artery. Those below the vocal folds drain into deep nodes associated with the inferior thyroid artery or with nodes associated with the front of the cricothyroid ligament or upper trachea. Sensory and motor innervation of the larynx is by two branches of the vagus nerves [X]—the superior laryngeal nerves and the recurrent laryngeal nerves (Fig. 8.228).


Anatomy_Gray

Anatomy_Gray. Sensory and motor innervation of the larynx is by two branches of the vagus nerves [X]—the superior laryngeal nerves and the recurrent laryngeal nerves (Fig. 8.228). The superior laryngeal nerves originate from the inferior vagal ganglia high in the neck (Fig. 8.228). On each side, the nerve descends medial to the internal carotid artery and divides into internal and external branches just above the level of the superior horn of the hyoid bone: The external branch (external laryngeal nerve) descends along the lateral wall of the pharynx to supply and penetrate the inferior constrictor of the pharynx and ends by supplying the cricothyroid muscle. The internal branch (internal laryngeal nerve) passes anteroinferiorly to penetrate the thyrohyoid membrane—it is mainly sensory and supplies the laryngeal cavity down to the level of the vocal folds.


Anatomy_Gray

Anatomy_Gray. The recurrent laryngeal nerves are (Fig. 8.228): sensory to the laryngeal cavity below the level of the vocal folds, and motor to all intrinsic muscles of the larynx except for the cricothyroid. The left recurrent laryngeal nerve originates in the thorax, whereas the right recurrent laryngeal nerve originates in the root of the neck. Both nerves generally ascend in the neck in the groove between the esophagus and trachea and enter the larynx deep to the margin of the inferior constrictor. They may pass medial to, lateral to, or through the lateral ligament of the thyroid gland, which attaches the thyroid gland to the trachea and lower part of the cricoid cartilage on each side. The two nasal cavities are the uppermost parts of the respiratory tract and contain the olfactory receptors. They are elongated wedge-shaped spaces with a large inferior base and a narrow superior apex (Figs. 8.229 and 8.230) and are held open by a skeletal framework consisting mainly of bone and cartilage.


Anatomy_Gray

Anatomy_Gray. The smaller anterior regions of the cavities are enclosed by the external nose, whereas the larger posterior regions are more central within the skull. The anterior apertures of the nasal cavities are the nares, which open onto the inferior surface of the nose. The posterior apertures are the choanae, which open into the nasopharynx. The nasal cavities are separated: from each other by a midline nasal septum, from the oral cavity below by the hard palate, and from the cranial cavity above by parts of the frontal, ethmoid, and sphenoid bones. Lateral to the nasal cavities are the orbits. Each nasal cavity has a floor, roof, medial wall, and lateral wall (Fig. 8.230A). The lateral wall is characterized by three curved shelves of bone (conchae), which are one above the other and project medially and inferiorly across the nasal cavity (Fig. 8.230B). The medial, anterior, and posterior margins of the conchae are free.


Anatomy_Gray

Anatomy_Gray. The conchae divide each nasal cavity into four air channels (Fig. 8.230C,D): an inferior nasal meatus between the inferior concha and the nasal floor, a middle nasal meatus between the inferior and middle concha, a superior nasal meatus between the middle and superior concha, and a spheno-ethmoidal recess between the superior concha and the nasal roof. These conchae increase the surface area of contact between tissues of the lateral wall and the respired air. The openings of the paranasal sinuses, which are extensions of the nasal cavity that erode into the surrounding bones during childhood and early adulthood, are on the lateral wall and roof of the nasal cavities (Fig. 8.231). In addition, the lateral wall also contains the opening of the nasolacrimal duct, which drains tears from the eye into the nasal cavity. Each nasal cavity consists of three general regions—the nasal vestibule, the respiratory region, and the olfactory region (Fig. 8.232):


Anatomy_Gray

Anatomy_Gray. Each nasal cavity consists of three general regions—the nasal vestibule, the respiratory region, and the olfactory region (Fig. 8.232): The nasal vestibule is a small dilated space just internal to the naris that is lined by skin and contains hair follicles. The respiratory region is the largest part of the nasal cavity, has a rich neurovascular supply, and is lined by respiratory epithelium composed mainly of ciliated and mucous cells. The olfactory region is small, is at the apex of each nasal cavity, is lined by olfactory epithelium, and contains the olfactory receptors.


Anatomy_Gray

Anatomy_Gray. The olfactory region is small, is at the apex of each nasal cavity, is lined by olfactory epithelium, and contains the olfactory receptors. In addition to housing receptors for the sense of smell (olfaction), the nasal cavities adjust the temperature and humidity of respired air by the action of a rich blood supply, and trap and remove particulate matter from the airway by filtering the air through hair in the vestibule and by capturing foreign material in abundant mucus. The mucus normally is moved posteriorly by cilia on epithelial cells in the nasal cavities and is swallowed. Innervation of the nasal cavities is by three cranial nerves: Olfaction is carried by the olfactory nerve [I]. General sensation is carried by the trigeminal nerve [V], the anterior region by the ophthalmic nerve [V1], and the posterior region by the maxillary nerve [V2].


Anatomy_Gray

Anatomy_Gray. General sensation is carried by the trigeminal nerve [V], the anterior region by the ophthalmic nerve [V1], and the posterior region by the maxillary nerve [V2]. All glands are innervated by parasympathetic fibers in the facial nerve [VII] (greater petrosal nerve), which join branches of the maxillary nerve [V2] in the pterygopalatine fossa. Sympathetic fibers are ultimately derived from the T1 spinal cord level. They synapse mainly in the superior cervical sympathetic ganglion, and postganglionic fibers reach the nasal cavities along blood vessels, or by joining branches of the maxillary nerve [V2] in the pterygopalatine fossa. Blood supply to the nasal cavities is by: terminal branches of the maxillary and facial arteries, which originate from the external carotid artery, and ethmoidal branches of the ophthalmic artery, which originates from the internal carotid artery.


Anatomy_Gray

Anatomy_Gray. Bones that contribute to the skeletal framework of the nasal cavities include: the unpaired ethmoid, sphenoid, frontal, and vomer bones, and the paired nasal, maxillary, palatine, and lacrimal bones and inferior conchae. Of all the bones associated with the nasal cavities, the ethmoid is a key element. The single ethmoid bone is one of the most complex bones in the skull. It contributes to the roof, lateral wall, and medial wall of both nasal cavities, and contains the ethmoidal cells (ethmoidal sinuses). The ethmoid bone is cuboidal in overall shape (Fig. 8.233A) and is composed of two rectangular box- shaped ethmoidal labyrinths, one on each side, united superiorly across the midline by a perforated sheet of bone (the cribriform plate). A second sheet of bone (the perpendicular plate) descends vertically in the median sagittal plane from the cribriform plate to form part of the nasal septum.


Anatomy_Gray

Anatomy_Gray. Each ethmoidal labyrinth is composed of two delicate sheets of bone, which sandwich between them the ethmoidal cells. The lateral sheet of bone (the orbital plate) is flat and forms part of the medial wall of the orbit. The medial sheet of bone forms the upper part of the lateral wall of the nasal cavity and is characterized by two processes and a swelling (Fig. 8.233B)—the two processes are curved shelves of bone (the superior and middle conchae), which project across the nasal cavity and curve downward ending in free medial margins, while inferior to the origin of the middle concha, the middle ethmoidal cells form a prominent bulge (the ethmoidal bulla), on the medial wall of the labyrinth.


Anatomy_Gray

Anatomy_Gray. Extending anterosuperiorly from just under the bulla is a groove (the ethmoidal infundibulum), which continues upward, and narrows to form a channel that penetrates the ethmoidal labyrinth and opens into the frontal sinus. This channel is for the frontonasal duct, which drains the frontal sinus. The superior surface of the ethmoidal labyrinth articulates with the frontal bone, which usually completes the roof of the ethmoidal cells, while the anterior surface articulates with the frontal process of the maxilla and with the lacrimal bone. The inferior surface articulates with the upper medial margin of the maxilla. A delicate irregularly shaped projection (the uncinate process) on the anterior aspect of the inferior surface of the ethmoidal labyrinth extends posteroinferiorly across a large defect (maxillary hiatus) in the medial wall of the maxilla to articulate with the inferior concha.


Anatomy_Gray

Anatomy_Gray. The cribriform plate is at the apex of the nasal cavities and fills the ethmoidal notch in the frontal bone (Fig. 8.233) and separates the nasal cavities below from the cranial cavity above. Small perforations in the bone allow the fibers of the olfactory nerve [I] to pass between the two regions. A large triangular process (the crista galli) at the midline on the superior surface of the cribriform plate anchors a fold (falx cerebri) of dura mater in the cranial cavity. The perpendicular plate of the ethmoid bone is quadrangular in shape, descends in the midline from the cribriform plate, and forms the upper part of the median nasal septum (Fig. 8.233). It articulates: posteriorly with the sphenoidal crest on the body of the sphenoid bone, anteriorly with the nasal spine on the frontal bone and with the site of articulation at the midline between the two nasal bones, and inferiorly and anteriorly with the septal cartilage and posteriorly with the vomer.


Anatomy_Gray

Anatomy_Gray. The external nose extends the nasal cavities onto the front of the face and positions the nares so that they point downward (Fig. 8.234). It is pyramidal in shape with its apex anterior in position. The upper angle of the nose between the openings of the orbits is continuous with the forehead. Like posterior regions, the anterior parts of the nasal cavities found within the nose are held open by a skeletal framework, which is composed partly of bone and mainly of cartilage: The bony parts are where the nose is continuous with the skull—here the nasal bones and parts of the maxillae and frontal bones provide support. Anteriorly, and on each side, support is provided by lateral processes of the septal cartilage, major alar and three or four minor alar cartilages, and a single septal cartilage in the midline that forms the anterior part of the nasal septum.


Anatomy_Gray

Anatomy_Gray. There are four paranasal air sinuses—the ethmoidal cells, and the sphenoidal, maxillary, and frontal sinuses (Fig. 8.235A,B). Each is named according to the bone in which it is found. The paranasal sinuses develop as outgrowths from the nasal cavities and erode into the surrounding bones. All of the paranasal sinuses: are lined by respiratory mucosa, which is ciliated and mucus secreting, open into the nasal cavities, and are innervated by branches of the trigeminal nerve [V]. The frontal sinuses, one on each side, are variable in size and are the most superior of the sinuses (Fig. 8.235A–C). Each is triangular in shape and is in the part of the frontal bone under the forehead. The base of each triangular sinus is oriented vertically in the bone at the midline above the bridge of the nose and the apex is laterally approximately one-third of the way along the upper margin of the orbit.


Anatomy_Gray

Anatomy_Gray. Each frontal sinus drains onto the lateral wall of the middle meatus via the frontonasal duct, which penetrates the ethmoidal labyrinth and continues as the ethmoidal infundibulum at the front end of the semilunar hiatus. The frontal sinuses are innervated by branches of the supra-orbital nerve from the ophthalmic nerve [V1]. Their blood supply is from branches of the anterior ethmoidal arteries. The ethmoidal cells on each side fill the ethmoidal labyrinth (Fig. 8.235A,B). Each cluster of cells is separated from the orbit by the thin orbital plate of the ethmoidal labyrinth, and from the nasal cavity by the medial wall of the ethmoidal labyrinth. The ethmoidal cells are formed by a variable number of individual air chambers, which are divided into anterior, middle, and posterior ethmoidal cells based on the location of their apertures on the lateral wall of the nasal cavity: The anterior ethmoidal cells open into the ethmoidal infundibulum or the frontonasal duct.


Anatomy_Gray

Anatomy_Gray. The anterior ethmoidal cells open into the ethmoidal infundibulum or the frontonasal duct. The middle ethmoidal cells open onto the ethmoidal bulla, or onto the lateral wall just above this structure. The posterior ethmoidal cells open onto the lateral wall of the superior nasal meatus. Because the ethmoidal cells often erode into bones beyond the boundaries of the ethmoidal labyrinth, their walls may be completed by the frontal, maxillary, lacrimal, sphenoid, and palatine bones. The ethmoidal cells are innervated by: the anterior and posterior ethmoidal branches of the nasociliary nerve from the ophthalmic nerve [V1], and the maxillary nerve [V2] via orbital branches from the pterygopalatine ganglion. The ethmoidal cells receive their blood supply through branches of the anterior and posterior ethmoidal arteries.


Anatomy_Gray

Anatomy_Gray. The ethmoidal cells receive their blood supply through branches of the anterior and posterior ethmoidal arteries. The maxillary sinuses, one on each side, are the largest of the paranasal sinuses and completely fill the bodies of the maxillae (Fig. 8.235A,B). Each is pyramidal in shape with the apex directed laterally and the base deep to the lateral wall of the adjacent nasal cavity. The medial wall or base of the maxillary sinus is formed by the maxilla, and by parts of the inferior concha and palatine bone that overlie the maxillary hiatus. The opening of the maxillary sinus is near the top of the base, in the center of the semilunar hiatus, which grooves the lateral wall of the middle nasal meatus. Relationships of the maxillary sinus are as follows: The superolateral surface (roof) is related above to the orbit. The anterolateral surface is related below to the roots of the upper molar and premolar teeth and in front to the face.


Anatomy_Gray

Anatomy_Gray. The superolateral surface (roof) is related above to the orbit. The anterolateral surface is related below to the roots of the upper molar and premolar teeth and in front to the face. The posterior wall is related behind to the infratemporal fossa. The maxillary sinuses are innervated by infra-orbital and alveolar branches of the maxillary nerve [V2], and receive their blood through branches from the infra-orbital and superior alveolar branches of the maxillary arteries. The sphenoidal sinuses, one on either side within the body of the sphenoid, open into the roof of the nasal cavity via apertures on the posterior wall of the spheno-ethmoidal recess (Fig. 8.235C,D). The apertures are high on the anterior walls of the sphenoid sinuses. The sphenoidal sinuses are related: above to the cranial cavity, particularly to the pituitary gland and to the optic chiasm, laterally, to the cranial cavity, particularly to the cavernous sinuses, and below and in front, to the nasal cavities.


Anatomy_Gray

Anatomy_Gray. Because only thin shelves of bone separate the sphenoidal sinuses from the nasal cavities below and hypophyseal fossa above, the pituitary gland can be surgically approached through the roof of the nasal cavities by passing first through the anteroinferior aspect of the sphenoid bone and into the sphenoidal sinuses and then through the top of the sphenoid bone into the hypophyseal fossa. Innervation of the sphenoidal sinuses is provided by: the posterior ethmoidal branch of the ophthalmic nerve [V1], and the maxillary nerve [V2] via orbital branches from the pterygopalatine ganglion. The sphenoidal sinuses are supplied by branches of the pharyngeal arteries from the maxillary arteries. Walls, floor, and roof The medial wall of each nasal cavity is the mucosa-covered surface of the thin nasal septum, which is oriented vertically in the median sagittal plane and separates the right and left nasal cavities from each other.


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Anatomy_Gray. The nasal septum (Fig. 8.236) consists of: the septal nasal cartilage anteriorly, posteriorly, mainly the vomer and the perpendicular plate of the ethmoid bone, small contributions by the nasal bones where they meet in the midline, and the nasal spine of the frontal bone, and contributions by the nasal crests of the maxillary and palatine bones, rostrum of the sphenoid bone, and the incisor crest of the maxilla. The floor of each nasal cavity (Fig. 8.237) is smooth, concave, and much wider than the roof. It consists of: soft tissues of the external nose, and the upper surface of the palatine process of the maxilla and the horizontal plate of the palatine bone, which together form the hard palate. The naris opens anteriorly into the floor, and the superior aperture of the incisive canal is deep to the mucosa immediately lateral to the nasal septum near the front of the hard palate.


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Anatomy_Gray. The naris opens anteriorly into the floor, and the superior aperture of the incisive canal is deep to the mucosa immediately lateral to the nasal septum near the front of the hard palate. The roof of the nasal cavity is narrow and is highest in central regions where it is formed by the cribriform plate of the ethmoid bone (Fig. 8.238). Anterior to the cribriform plate the roof slopes inferiorly to the nares and is formed by: the nasal spine of the frontal bone and the nasal bones, and the lateral processes of the septal cartilage and major alar cartilages of the external nose. Posteriorly, the roof of each cavity slopes inferiorly to the choana and is formed by: the anterior surface of the sphenoid bone, the ala of the vomer and adjacent sphenoidal process of the palatine bone, and the vaginal process of the medial plate of the pterygoid process.


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Anatomy_Gray. Underlying the mucosa, the roof is perforated superiorly by openings in the cribriform plate, and anterior to these openings by a separate foramen for the anterior ethmoidal nerve and vessels. The opening between the sphenoidal sinus and the spheno-ethmoidal recess is on the posterior slope of the roof. The lateral wall of each nasal cavity is complex and is formed by bone, cartilage, and soft tissues. Bony support for the lateral wall (Fig. 8.239A) is provided by: the ethmoidal labyrinth, superior concha, middle concha and uncinate process, the perpendicular plate of the palatine bone, the medial pterygoid plate of the sphenoid bone, the medial surfaces of the lacrimal bones and maxillae, and the inferior concha.


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Anatomy_Gray. In the external nose, the lateral wall of the cavity is supported by cartilage (lateral process of the septal cartilage and major and minor alar cartilages) and by soft tissues. The surface of the lateral wall is irregular in contour and is interrupted by the three nasal conchae. The inferior, middle, and superior conchae (Fig. 8.239B) extend medially across the nasal cavity, separating it into four air channels, an inferior, middle, and superior meatus and a spheno-ethmoidal recess. The conchae do not extend forward into the external nose. The anterior end of each concha curves inferiorly to form a lip that overlies the end of the related meatus. Immediately inferior to the attachment of the middle concha and just anterior to the midpoint of the concha, the lateral wall of the middle meatus elevates to form the dome-shaped ethmoidal bulla (Fig. 8.239C). This is formed by the underlying middle ethmoidal cells, which expand the medial wall of the ethmoidal labyrinth.


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Anatomy_Gray. Inferior to the ethmoidal bulla is a curved gutter (the semilunar hiatus), which is formed by the mucosa covering the lateral wall as it spans a defect in the bony wall between the ethmoidal bulla above and the uncinate process below. The anterior end of the semilunar hiatus forms a channel (the ethmoidal infundibulum), which curves upward and continues as the frontonasal duct through the anterior part of the ethmoidal labyrinth to open into the frontal sinus. The nasolacrimal duct and most of the paranasal sinuses open onto the lateral wall of the nasal cavity (Fig. 8.239C): The nasolacrimal duct opens onto the lateral wall of the inferior nasal meatus under the anterior lip of the inferior concha—it drains tears from the conjunctival sac of the eye into the nasal cavity and originates at the inferior end of the lacrimal sac on the anteromedial wall of the orbit.


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Anatomy_Gray. The frontal sinus drains via the frontonasal duct and ethmoidal infundibulum into the anterior end of the semilunar hiatus on the lateral wall of the middle nasal meatus—the anterior ethmoidal cells drain into the frontonasal duct or ethmoidal infundibulum (in some cases, the frontal sinus drains directly into the anterior end of the middle nasal meatus and the frontonasal duct ends blindly in the anterior ethmoidal cells). The middle ethmoidal cells open onto or just above the ethmoidal bulla. The posterior ethmoidal cells usually open onto the lateral wall of the superior nasal meatus. The large maxillary sinus opens into the semilunar hiatus, usually just inferior to the center of the ethmoidal bulla—this opening is near the roof of the maxillary sinus. The only paranasal sinus that does not drain onto the lateral wall of the nasal cavity is the sphenoidal sinus, which usually opens onto the sloping posterior roof of the nasal cavity.


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Anatomy_Gray. The only paranasal sinus that does not drain onto the lateral wall of the nasal cavity is the sphenoidal sinus, which usually opens onto the sloping posterior roof of the nasal cavity. The nares are oval apertures on the inferior aspect of the external nose and are the anterior openings of the nasal cavities (Fig. 8.240A). They are held open by the surrounding alar cartilages and septal cartilage, and by the inferior nasal spine and adjacent margins of the maxillae. Although the nares are continuously open, they can be widened further by the action of the related muscles of facial expression (nasalis, depressor septi nasi, and levator labii superioris alaeque nasi muscles; Fig. 8.240B).


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Anatomy_Gray. The choanae are the oval-shaped openings between the nasal cavities and the nasopharynx (Fig. 8.241). Unlike the nares, which have flexible borders of cartilage and soft tissues, the choanae are rigid openings completely surrounded by bone, and their margins are formed: inferiorly by the posterior border of the horizontal plate of the palatine bone, laterally by the posterior margin of the medial plate of the pterygoid process, and medially by the posterior border of the vomer. The roof of the choanae is formed: anteriorly by the ala of the vomer and the vaginal process of the medial plate of the pterygoid process, and posteriorly by the body of the sphenoid bone. There are a number of routes by which nerves and vessels enter and leave the soft tissues lining each nasal cavity (Fig. 8.242), and these include the cribriform plate, sphenopalatine foramen, incisive canal, and small foramina in the lateral wall, and around the margin of the nares.


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Anatomy_Gray. The fibers of the olfactory nerve [I] exit the nasal cavity and enter the cranial cavity through perforations in the cribriform plate. In addition, small foramina between the cribriform plate and surrounding bone allow the anterior ethmoidal nerve, a branch of the ophthalmic nerve [V1], and accompanying vessels to pass from the orbit into the cranial cavity and then down into the nasal cavity. In addition, there is a connection in some individuals between nasal veins and the superior sagittal sinus of the cranial cavity through a prominent foramen (the foramen cecum) in the midline between the crista galli and frontal bone.


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Anatomy_Gray. One of the most important routes by which nerves and vessels enter and leave the nasal cavity is the sphenopalatine foramen in the posterolateral wall of the superior nasal meatus. This foramen is just superior to the attachment of the posterior end of the middle nasal concha and is formed by the sphenopalatine notch in the palatine bone and the body of the sphenoid bone. The sphenopalatine foramen is a route of communication between the nasal cavity and the pterygopalatine fossa. Major structures passing through the foramen are: the sphenopalatine branch of the maxillary artery, the nasopalatine branch of the maxillary nerve [V2], and superior nasal branches of the maxillary nerve [V2].


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Anatomy_Gray. Another route by which structures enter and leave the nasal cavities is through the incisive canal in the floor of each nasal cavity. This canal is immediately lateral to the nasal septum and just posterosuperior to the root of the central incisor in the maxilla. The two incisive canals, one on each side, both open into the single unpaired incisive fossa in the roof of the oral cavity and transmit: the nasopalatine nerve from the nasal cavity into the oral cavity, and the terminal end of the greater palatine artery from the oral cavity into the nasal cavity. Small foramina in the lateral wall Other routes by which vessels and nerves get into and out of the nasal cavity include the nares and small foramina in the lateral wall: Internal nasal branches of the infra-orbital nerve of the maxillary nerve [V2] and alar branches of the nasal artery from the facial artery loop around the margin of the naris to gain entry to the lateral wall of the nasal cavity from the face.


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Anatomy_Gray. Inferior nasal branches from the greater palatine branch of the maxillary nerve [V2] enter the lateral wall of the nasal cavity from the palatine canal by passing through small foramina on the lateral wall. The nasal cavities have a rich vascular supply for altering the humidity and temperature of respired air. In fact, the submucosa of the respiratory region, particularly that related to the conchae and septum, is often described as “erectile” or “cavernous” because the tissue enlarges or shrinks depending on the amount of blood flowing into the system. Arteries that supply the nasal cavity include vessels that originate from both the internal and external carotid arteries (Fig. 8.243): Vessels that originate from branches of the external carotid artery include the sphenopalatine, greater palatine, superior labial, and lateral nasal arteries. Vessels that originate from branches of the internal carotid artery are the anterior and posterior ethmoidal arteries.


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Anatomy_Gray. Vessels that originate from branches of the internal carotid artery are the anterior and posterior ethmoidal arteries. The largest vessel supplying the nasal cavity is the sphenopalatine artery (Fig. 8.243), which is the terminal branch of the maxillary artery in the pterygopalatine fossa. It leaves the pterygopalatine fossa and enters the nasal cavity by passing medially through the sphenopalatine foramen and onto the lateral wall of the nasal cavity. Posterior lateral nasal branches supply a large part of the lateral wall and anastomose anteriorly with branches from the anterior and posterior ethmoidal arteries, and with lateral nasal branches of the facial artery.


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Anatomy_Gray. Posterior septal branches of the sphenopalatine artery pass over the roof of the cavity and onto the nasal septum where they contribute to the blood supply of the medial wall. One of these latter branches continues forward down the nasal septum to anastomose with the terminal end of the greater palatine artery and septal branches of the superior labial artery. The terminal end of the greater palatine artery enters the anterior aspect of the floor of the nasal cavity by passing up through the incisive canal from the roof of the oral cavity (Fig. 8.243).


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Anatomy_Gray. The terminal end of the greater palatine artery enters the anterior aspect of the floor of the nasal cavity by passing up through the incisive canal from the roof of the oral cavity (Fig. 8.243). Like the sphenopalatine artery, the greater palatine artery arises in the pterygopalatine fossa as a branch of the maxillary artery. It passes first onto the roof of the oral cavity by passing down through the palatine canal and greater palatine foramen to the posterior aspect of the palate, then passes forward on the undersurface of the palate, and up through the incisive fossa and canal to reach the floor of the nasal cavity. The greater palatine artery supplies anterior regions of the medial wall and adjacent floor of the nasal cavity, and anastomoses with the septal branch of the sphenopalatine artery. The superior labial artery and the lateral nasal artery originate from the facial artery on the front of the face.


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Anatomy_Gray. The superior labial artery and the lateral nasal artery originate from the facial artery on the front of the face. The superior labial artery originates from the facial artery near the lateral end of the oral fissure and passes medially in the lip, supplying the lip and giving rise to branches that supply the nose and nasal cavity. An alar branch supplies the region around the lateral aspect of the naris and a septal branch passes into the nasal cavity and supplies anterior regions of the nasal septum. The lateral nasal artery originates from the facial artery in association with the margin of the external nose and contributes to the blood supply of the external nose. Alar branches pass around the lateral margin of the naris and supply the nasal vestibule.


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Anatomy_Gray. The anterior and posterior ethmoidal arteries (Fig. 8.243) originate in the orbit from the ophthalmic artery, which originates in the cranial cavity as a major branch of the internal carotid artery. They pass through canals in the medial wall of the orbit between the ethmoidal labyrinth and frontal bone, supply the adjacent paranasal sinuses, and then enter the cranial cavity immediately lateral and superior to the cribriform plate. The posterior ethmoidal artery descends into the nasal cavity through the cribriform plate and has branches to the upper parts of the medial and lateral walls.


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Anatomy_Gray. The posterior ethmoidal artery descends into the nasal cavity through the cribriform plate and has branches to the upper parts of the medial and lateral walls. The anterior ethmoidal artery passes forward, with the accompanying anterior ethmoidal nerve, in a groove on the cribriform plate and enters the nasal cavity by descending through a slit-like foramen immediately lateral to the crista galli. It gives rise to branches that supply the medial (septal) and lateral wall of the nasal cavity and then continues forward on the deep surface of the nasal bone, and terminates by passing between the nasal bone and lateral nasal cartilage to emerge on the external nose as the external nasal branch to supply skin and adjacent tissues.


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Anatomy_Gray. Vessels that supply the nasal cavities form extensive anastomoses with each other. This is particularly evident in the anterior region of the medial wall where there are anastomoses between branches of the greater palatine, sphenopalatine, superior labial, and anterior ethmoidal arteries, and where the vessels are relatively close to the surface (Fig. 8.243B). This area is the major site of nosebleeds, or epistaxis. Veins draining the nasal cavities generally follow the arteries (Fig. 8.244): Veins that pass with branches that ultimately originate from the maxillary artery drain into the pterygoid plexus of veins in the infratemporal fossa. Veins from anterior regions of the nasal cavities join the facial vein.


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Anatomy_Gray. Veins from anterior regions of the nasal cavities join the facial vein. In some individuals, an additional nasal vein passes superiorly through a midline aperture (the foramen cecum), in the frontal bone anterior to the crista galli, and joins with the anterior end of the superior sagittal sinus. Because this nasal vein connects an intracranial venous sinus with extracranial veins, it is classified as an emissary vein. Emissary veins in general are routes by which infections can track from peripheral regions into the cranial cavity. Veins that accompany the anterior and posterior ethmoidal arteries are tributaries of the superior ophthalmic vein, which is one of the largest emissary veins and drains into the cavernous sinus on either side of the hypophyseal fossa. Nerves that innervate the nasal cavities (Fig. 8.245) are: the olfactory nerve [I] for olfaction, and branches of the ophthalmic [V1] and maxillary [V2] nerves for general sensation.


Anatomy_Gray

Anatomy_Gray. Nerves that innervate the nasal cavities (Fig. 8.245) are: the olfactory nerve [I] for olfaction, and branches of the ophthalmic [V1] and maxillary [V2] nerves for general sensation. Secretomotor innervation of mucous glands in the nasal cavities and paranasal sinuses is by parasympathetic fibers from the facial nerve [VII], which mainly join branches of the maxillary nerve [V2] in the pterygopalatine fossa. The olfactory nerve [I] is composed of axons from receptors in the olfactory epithelium at the top of each nasal cavity. Bundles of these axons pass superiorly through perforations in the cribriform plate to synapse with neurons in the olfactory bulb of the brain. Branches from the ophthalmic nerve [V1] Branches from the ophthalmic nerve [V1] that innervate the nasal cavity are the anterior and posterior ethmoidal nerves, which originate from the nasociliary nerve in the orbit.


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Anatomy_Gray. The anterior ethmoidal nerve (Fig. 8.245) travels with the anterior ethmoidal artery and leaves the orbit through a canal between the ethmoidal labyrinth and the frontal bone. It passes through and supplies the adjacent ethmoidal cells and frontal sinus, and then enters the cranial cavity immediately lateral and superior to the cribriform plate. It then travels forward in a groove on the cribriform plate and enters the nasal cavity by descending through a slit-like foramen immediately lateral to the crista galli. It has branches to the medial and lateral wall of the nasal cavity and then continues forward on the undersurface of the nasal bone. It passes onto the external surface of the nose by traveling between the nasal bone and lateral nasal cartilage, and then terminates as the external nasal nerve, which supplies skin around the naris, in the nasal vestibule, and on the tip of the nose.


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Anatomy_Gray. Like the anterior ethmoidal nerve, the posterior ethmoidal nerve leaves the orbit through a similar canal in the medial wall of the orbit. It terminates by supplying the mucosa of the ethmoidal cells and sphenoidal sinus and normally does not extend into the nasal cavity itself. Branches from the maxillary nerve [V2] A number of nasal branches from the maxillary nerve [V2] innervate the nasal cavity. Many of these nasal branches (Fig. 8.245) originate in the pterygopalatine fossa, which is just lateral to the lateral wall of the nasal cavity, and leave the fossa to enter the nasal cavity by passing medially through the sphenopalatine foramen or through smaller foramina in the lateral wall: A number of these nerves (posterior superior lateral nasal nerves) pass forward on and supply the lateral wall of the nasal cavity. Others (posterior superior medial nasal nerves) cross the roof to the nasal septum and supply both these regions.


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Anatomy_Gray. Others (posterior superior medial nasal nerves) cross the roof to the nasal septum and supply both these regions. The largest of these nerves is the nasopalatine nerve, which passes forward and down the medial wall of the nasal cavity to pass through the incisive canal onto the roof of the oral cavity, and terminates by supplying the oral mucosa posterior to the incisor teeth. Other nasal nerves (posterior inferior nasal nerves) originate from the greater palatine nerve, descending from the pterygopalatine fossa in the palatine canal just lateral to the nasal cavity, and pass through small bony foramina to innervate the lateral wall of the nasal cavity. A small nasal nerve also originates from the anterior superior alveolar branch of the infra-orbital nerve and passes medially through the maxilla to supply the lateral wall near the anterior end of the inferior concha.


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Anatomy_Gray. Secretomotor innervation of glands in the mucosa of the nasal cavity and paranasal sinuses is by preganglionic parasympathetic fibers carried in the greater petrosal branch of the facial nerve [VII]. These fibers enter the pterygopalatine fossa and synapse in the pterygopalatine ganglion (see Fig. 8.157 and pp. 986–987). Postganglionic parasympathetic fibers then join branches of the maxillary nerve [V2] to leave the fossa and ultimately reach target glands.


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Anatomy_Gray. Sympathetic innervation, mainly involved with regulating blood flow in the nasal mucosa, is from spinal cord level T1. Preganglionic sympathetic fibers enter the sympathetic trunk and ascend to synapse in the superior cervical sympathetic ganglion. Postganglionic sympathetic fibers pass onto the internal carotid artery, enter the cranial cavity, and then leave the internal carotid artery to form the deep petrosal nerve, which joins the greater petrosal nerve of the facial nerve [VII] and enters the pterygopalatine fossa (see Figs. 8.156 and 8.157 and pp. 984–986). Like the parasympathetic fibers, the sympathetic fibers follow branches of the maxillary nerve [V2] into the nasal cavity. Lymph from anterior regions of the nasal cavities drains forward onto the face by passing around the margins of the nares (Fig. 8.246). These lymphatics ultimately connect with the submandibular nodes.


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Anatomy_Gray. Lymph from posterior regions of the nasal cavity and the paranasal sinuses drains into upper deep cervical nodes. Some of this lymph passes first through the retropharyngeal nodes. The oral cavity is inferior to the nasal cavities (Fig. 8.247A). It has a roof and floor and lateral walls, opens onto the face through the oral fissure, and is continuous with the cavity of the pharynx at the oropharyngeal isthmus. The roof of the oral cavity consists of the hard and soft palates. The floor is formed mainly of soft tissues, which include a muscular diaphragm and the tongue. The lateral walls (cheeks) are muscular and merge anteriorly with the lips surrounding the oral fissure (the anterior opening of the oral cavity). The posterior aperture of the oral cavity is the oropharyngeal isthmus, which opens into the oral part of the pharynx.


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Anatomy_Gray. The posterior aperture of the oral cavity is the oropharyngeal isthmus, which opens into the oral part of the pharynx. The oral cavity is separated into two regions by the upper and lower dental arches consisting of the teeth and alveolar bone that supports them (Fig. 8.247B): The outer oral vestibule, which is horseshoe shaped, is between the dental arches and the deep surfaces of the cheeks and lips—the oral fissure opens into it and can be opened and closed by muscles of facial expression, and by movements of the lower jaw. The inner oral cavity proper is enclosed by the dental arches. The degree of separation between the upper and lower arches is established by elevating or depressing the lower jaw (mandible) at the temporomandibular joint. The oropharyngeal isthmus at the back of the oral cavity proper can be opened and closed by surrounding soft tissues, which include the soft palate and tongue. The oral cavity has multiple functions:


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Anatomy_Gray. The oral cavity has multiple functions: It is the inlet for the digestive system involved with the initial processing of food, which is aided by secretions from salivary glands. It manipulates sounds produced by the larynx and one outcome of this is speech. It can be used for breathing because it opens into the pharynx, which is a common pathway for food and air. For this reason, the oral cavity can be used by physicians to access the lower airway, and dentists use “rubber dams” to prevent debris such as tooth fragments from passing through the oropharyngeal isthmus and pharynx into either the esophagus or the lower airway. Multiple nerves innervate the oral cavity General sensory innervation is carried predominantly by branches of the trigeminal nerve [V]: The upper parts of the cavity, including the palate and the upper teeth, are innervated by branches of the maxillary nerve [V2].


Anatomy_Gray

Anatomy_Gray. The upper parts of the cavity, including the palate and the upper teeth, are innervated by branches of the maxillary nerve [V2]. The lower parts, including the teeth and oral part of the tongue, are innervated by branches of the mandibular nerve [V3]. Taste (special afferent [SA]) from the oral part or anterior two-thirds of the tongue is carried by branches of the facial nerve [VII], which join and are distributed with branches of the trigeminal nerve [V]. Parasympathetic fibers to the glands within the oral cavity are also carried by branches of the facial nerve [VII], which are distributed with branches of the trigeminal nerve [V]. Sympathetic fibers in the oral cavity ultimately come from spinal cord level T1, synapse in the superior cervical sympathetic ganglion, and are eventually distributed to the oral cavity along branches of the trigeminal nerve [V] or directly along blood vessels.


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Anatomy_Gray. All muscles of the tongue are innervated by the hypoglossal nerve [XII], except the palatoglossus, which is innervated by the vagus nerve [X]. All muscles of the soft palate are innervated by the vagus nerve [X], except for the tensor veli palatini, which is innervated by a branch from the mandibular nerve [V3]. The muscle (mylohyoid) that forms the floor of the oral cavity is also innervated by the mandibular nerve [V3]. Bones that contribute to the skeletal framework of the oral cavity or are related to the anatomy of structures in the oral cavity include: the paired maxillae, palatine, and temporal bones, and the unpaired mandible, sphenoid, and hyoid bones. In addition, the cartilaginous parts of the pharyngotympanic tubes on the inferior aspect of the base of the skull are related to the attachment of muscles of the soft palate.


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Anatomy_Gray. In addition, the cartilaginous parts of the pharyngotympanic tubes on the inferior aspect of the base of the skull are related to the attachment of muscles of the soft palate. The two maxillae contribute substantially to the architecture of the roof of the oral cavity. The parts involved are the alveolar and palatine processes (Fig. 8.248A). The palatine process is a horizontal shelf that projects from the medial surface of each maxilla. It originates just superior to the medial aspect of the alveolar process and extends to the midline where it is joined, at a suture, with the palatine process from the other side. Together, the two palatine processes form the anterior two-thirds of the hard palate.


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Anatomy_Gray. In the midline on the inferior surface of the hard palate and at the anterior end of the intermaxillary suture is a single small fossa (incisive fossa) just behind the incisor teeth. Two incisive canals, one on each side, extend posterosuperiorly from the roof of this fossa to open onto the floor of the nasal cavity. The canals and fossae allow passage of the greater palatine vessels and the nasopalatine nerves. The parts of each L-shaped palatine bone that contribute to the roof of the oral cavity are the horizontal plate and the pyramidal process (Fig. 8.248A). The horizontal plate projects medially from the inferior aspect of the palatine bone and is joined by sutures to its partner in the midline and, on the same side, with the palatine process of the maxilla anteriorly.


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Anatomy_Gray. A single posterior nasal spine is formed at the midline where the two horizontal plates join and projects backward from the margin of the hard palate. The posterior margin of the horizontal plates and the posterior nasal spine are associated with attachment of the soft palate. The greater palatine foramen, formed mainly by the horizontal plate of the palatine bone and completed laterally by the adjacent part of the maxilla, opens onto the posterolateral aspect of the horizontal plate. This foramen is the inferior opening of the palatine canal, which continues superiorly into the pterygopalatine fossa and transmits the greater palatine nerve and vessels to the palate. Also opening onto the palatine bone is the lesser palatine foramen. This foramen is the inferior opening of the short lesser palatine canal, which branches from the greater palatine canal and transmits the lesser palatine nerve and vessels to the soft palate.