, SOFT , AND (Grant's Dissector [16th Ed.] pp. 286-290, 294-299, 303-307)

TODAY’S GOALS: 1. Disarticulate the head and cervical visceral compartment from the cervical spine 2. Identify the buccopharyngeal , the cervical visceral compartment, the prevertebral compartment, and the 3. Identify the sympathetic trunk, cranial , and vessels ascending/descending along the lateral pharyngeal wall from the skull into the 4. Identify the 3 parts of the pharynx (nasopharynx, oropharynx, laryngopharynx) and associated structures related to each 5. Identify the muscles of the pharyngeal wall 6. Identify the hard and soft and associated musculature 7. Identify the openings of the auditory tube and sphenopalatine foramen and the and blood supply to the and hard and 8. Identify the principal cartilages, membranes, and synovial joints of the larynx 9. Identify the principal intrinsic muscles of the larynx 10. Identify the internal, external, and recurrent laryngeal nerves 11. Identify the vestibular and vocal folds, rima glottidis, and 3 cavities within the larynx

DISSECTION NOTES: General comments: The pharynx (aka “”) is a funnel-shaped region in the head and neck that communicates anteriorly with the , oral cavity, and larynx. It is a common space for the upper respiratory and digestive systems before these systems separate into their respective “tubes” (i.e., larynx/ and ). In order to study the pharyngeal wall and structures related to it, the head and cervical visceral compartment must first be disarticulated from the cervical spine. Use the following instructions to perform this disarticulation.

I. Disarticulation of the Head and Cervical Visceral Compartment

Step 1. Dissect the sternocleidomastoid and posterior digastric muscles to the mastoid process. DO NOT REFLECT THESE ATTACHMENTS. These muscles will accompany the viscerocranium anteriorly.

27 Step 2. Insert the fingers of both hands posterior to the carotid sheaths and push them medially until they meet posterior to the cervical viscera. Your fingers are now in the retropharyngeal/retrovisceral space. Work your fingers superiorly to the base of the skull and inferiorly toward the superior mediastinum.

Step 3. Isolate and protect the contents of the jugular foramen, taking care not to cut CNs IX, X, and XI, internal jugular vein, and internal carotid artery (contents of the at this level). These structures will also accompany the viscerocranium forwards.

Step 4. View the posterior cranial fossa on your cadaver and refer to the above diagram. Plan your saw cuts by incising the dura parallel to the petrous ridge of the temporal bone so that your scalpel passes between the jugular foramen and the foramen magnum near the hypoglossal canal.

Step 5. Follow the scalpel marks with a hand saw. Saw through the occipital bone on both sides keeping the saw cut posterior to the mastoid process. The saw cuts should reach the midline in front of the foramen magnum.

Step 6. Carefully pull the viscerocranium anteriorly and cut remaining muscular and fascial attachments. This should produce a view similar to Fig. 7.64 in the Dissector (p. 288).

II. Pharynx A. Posterior aspect of the pharyngeal wall. Note and identify the following: • – this fascia is a continuation of the fascia overlying the buccinator muscle and covers the posterior pharyngeal wall musculature (it is the posterior portion of the cervical visceral fascia). Carefully strip away this fascia to identify the following muscles, nerves, and vessels: • Pharyngeal constrictors: Paired skeletal muscles that insert into the posterior midline at the . (Dissector p. 287, Fig. 7.63; p. 290, Table 7.7) o Superior constrictor – its principal attachment site anteriorly is the (a thin fibrous “seam” that it shares with the buccinator muscle). It attaches posteriorly to the pharyngeal raphe and to the pharyngeal tubercle in the superior midline. This muscle is deficient superiorly and does not directly attach to the skull. Rather, the interval between its superior border and the skull base is filled by dense connective tissue called the . o Middle constrictor – its principal anterior attachment is the greater horn of the hyoid. Its upper fibers overlap the lower fibers of the superior constrictor. o Inferior constrictor – its principal anterior attachment is the oblique line of the thyroid cartilage and lateral surface of the cricoid cartilage. Its upper fibers overlap the lower fibers of the middle constrictor. • Palpate the superolateral region of the pharynx for the slender styloid process (Dissector p. 287, Fig. 7.63). Using this as a landmark, use blunt dissection to locate and identify the that attaches to its medial surface. Observe the glossopharyngeal nerve descending on the posterior surface of this muscle before wrapping around it laterally (Dissector p. 288, Fig. 7.64). Follow these two structures inferiorly where they pass between the superior and middle

28 constrictor muscles to the inner surface of the pharyngeal wall. This is one of the longitudinal muscles of the pharynx. • Identify CNs IX, X, XI where they exit the jugular foramen medial to the internal jugular vein (IJV) (Dissector p. 288, Fig. 7.64). Confirm their identification by following them into the neck where they were previously dissected. • Identify the • Identify the sympathetic trunk and the superior cervical ganglion. This ganglion is fusiform in appearance and is the largest of the cervical sympathetic ganglia. Look for the internal carotid nerve leaving its superior end and coursing with the internal carotid artery to the carotid canal. This nerve forms the internal carotid nerve plexus on the surface of ICA. • Identify the internal jugular vein. The carotid sheath ends superiorly at the opening of the carotid canal and jugular foramen and encloses IJV, ICA, and the proximal portions of CNs IX, X, XI. The connective tissue of this sheath is necessarily removed to visualize these structures.

III. Internal Inspection of the Pharynx A. Once you have identified the and associated nerves and vessels descending along its lateral border, divide the posterior pharyngeal wall in its midline (along pharyngeal raphe) by cutting through it with scissors or scalpel from the base of skull (clivus) to the esophagus. B. As you look through this incision, identify the three parts of the pharynx: nasopharynx, oropharynx, laryngopharynx (hypopharynx), and their communications with the nasal cavity, oral cavity, and larynx. C. Identify the following in a superior to inferior direction (many of these will be revisited after the skull has been bisected, allowing a better view of the interior of the head and pharynx) : • Choana or posterior nasal aperture – the narrow passageway on either side of the nasal septum that communicates the nasal cavity with the nasopharynx • Uvula and soft palate • Posterior 1/3 of the • and epiglottic valleculae o The root of the tongue is connected to the anterior border of the epiglottis via the: Median glossoepiglottic fold (single) Lateral glossoepiglottic folds (paired) Valleculae – the shallow depressions located between the median and lateral glossoepiglottic folds. They are depressions that ingested foreign bodies may become enlodged in. • Inlet/aditus of larynx – this is the opening from the laryngopharynx into the larynx. It is bounded anteriorly by the epiglottis and laterally by a pair of mucosal folds called the aryepiglottic folds. Lateral to the aryepiglottic folds are the : Piriform recesses – additional sites for enlodgement of ingested foreign objects.

29 IV. Bisection of the Head (To preserve the work that was done on the orbit [assuming one orbit was dissected], bisection will be performed on the opposite side. The goal is to divide the head in the sagittal plane to produce one side that contains an intact nasal septum and another side that exposes the lateral nasal wall for study of the oral and nasal cavities in the next lab session.) Read through these instructions before proceeding to understand where your scalpel and saw cuts will be made. First, make the following cuts using a scalpel:

A. Divide the uvula and soft palate in the midline. B. Cut through the upper in the midline and through the nostril and nasal cartilage, parallel to the nasal septum on the side the saw cut will be made. C. Position a handsaw blade just lateral to the crista galli and keep the blade close to the nasal septum as you progress. Proceed to cut from superior to inferior through the frontal and nasal bones, the cribriform plate, the midline of the body of the sphenoid, the clivus, and the . The two superior halves of the head should separate from each other. D. Next, divide the tongue in the midline using a scalpel and similarly divide the lower lip in the midline between the central incisors. Place a saw blade between the cut edges and saw through the mandible between the two central incisors. Do not cut through the hyoid bone or larynx. The two halves should now fall away enabling you to inspect and further dissect the lateral pharyngeal wall and soft palate areas.

V. Lateral Pharyngeal Wall A. Review the regions of the pharynx: nasopharynx, oropharynx, laryngopharynx and inspect the following with the mucosa intact (Dissector pp. 289, 296; Figs. 7.65, 7.77): 1. Nasopharynx a. Choana/posterior nasal aperture b. Torus tubarius (a projection of the auditory tube cartilage along the lateral wall of the nasopharynx) and opening of the auditory tube posterior to the inferior concha. The auditory tube (pharyngotympanic tube) connects the nasopharynx to the middle ear (tympanic) cavity. The part of this tube closest to the pharynx is cartilaginous (about 2/3s of its length); the part closest to the middle ear passes through temporal bone. c. Salpingopharyngeal fold - a tiny mucosal fold (containing a muscle of the same name) extending inferiorly from the torus tubarius to the lateral pharyngeal wall d. Pharyngeal recess (posterior to torus tubarius) and location of the pharyngeal tonsil (adenoid) beneath the mucosal membrane of this recess 2. Oropharynx a. Palatoglossal fold – a mucosal fold that extends from the lateral margin of the soft palate to the lateral margin of the tongue near the junction of its anterior 2/3s and posterior 1/3 parts. b. Palatopharyngeal fold – a broad mucosal fold (containing the ) that extends from the lateral margin of the soft palate to the lateral pharyngeal wall c. Palatine tonsil – located (if present) between the palatoglossal and palatopharyngeal folds

30 3. Laryngopharynx a. Epiglottis - the “leaf-shaped” cartilage of the larynx that extends upward and attaches to the root of the tongue via mucosal (glossoepiglottic folds) b. Median and lateral glossoepiglottic folds c. Valleculae d. Aryepiglottic folds e. Piriform recesses f. Aditus of larynx

B. Strip away the mucosa of the lateral pharyngeal wall and identify (Dissector p. 296, Fig. 7.78): 1. Superior constrictor 2. Middle constrictor 3. Salpingopharyngeus 4. Palatopharyngeus 5. Palatoglossus 6. Stylopharyngeus – enters the pharyngeal wall between the superior and middle constrictors and lies vertically anterior to the palatopharyngeus muscle 7. Glossopharyngeal nerve – enters the oropharynx by passing between the superior and middle constrictors. Attempt to find its tonsillar and lingual branches to the mucosa of the palatine tonsil area and posterior third of the tongue, respectively.

VI. Soft Palate A. Proceed to gently strip mucosa from the nasal and oral surfaces of the soft palate and identify (Dissector pp. 296, 297; Figs. 7.78, 7.79; p. 299, Table 7.8): 1. Levator veli palatini muscle – note the ridge (torus levatorius) emerging from the floor of auditory tube opening. Beneath this ridge identify this fleshy muscle into superior portion of the soft palate. 2. Tensor veli palatini muscle – palpate the posterior border of the medial pterygoid plate and remove overlying mucosa to observe muscle fibers of the tensor veli palatini descending along the lateral surface of this plate. Follow this muscle inferiorly and observe its tendon turning medially around the hamulus of the medial pterygoid plate into the soft palate. 3. Palatoglossus – a small muscle within the palatoglossal fold. This is also a “cross- over” muscle of the tongue and is innervated by the . 4. Palatopharyngeus – a muscle within the palatopharyngeal fold. This is also a “cross- over” muscle of the pharynx and is innervated by the vagus nerve. 5. Musculus uvulae – a slender pair of muscles extending from the posterior nasal spine of the hard palate into the midline uvula. 6. All muscles of the soft palate are innervated by CN X, except TVP, which is innervated by CN V3.

31 B. Sensory nerve and blood supply to the hard and soft palate (Dissector pp. 297, 298; Figs. 7.79, 7.80) 1. Greater and lesser palatine nerves and arteries • Attempt to find these nerves and arteries by using a probe to separate the mucosa from the inferior surface of the hard palate where it was cut during the bisection • Medial to the 3rd maxillary molar identify the greater and lesser palatine nerves and arteries emerging from their respective foramina – the and artery supply much of the hard palate, while the lesser palatine nerve and artery supply the soft palate

VII. Larynx

DISSECTION NOTES: General comments: The larynx is the gateway to the airway and contains the glottis, a valve that regulates the size of the glottic opening for breathing and phonation. The larynx consists of numerous cartilages, two pairs of synovial joints, membranes, and intrinsic muscles (Dissector p. 307, Table 7.10). Beneath its intrinsic muscles modify the glottic opening.

A. In the anterior view of the neck: • Review the overlying the larynx (sternohyoid, superior belly of omohyoid, sternothyroid, thyrohyoid) • Review the thyrohyoid and cricothyroid membranes • Review the thyroid cartilage (laminae, superior thyroid notch, laryngeal prominence [Adam’s apple]); cricoid cartilage (arch) • Identify the o Inferior attachment: lateral surface of cricoid o Superior attachment: inferior margin of thyroid cartilage o Action: tilts the thyroid cartilage anteriorly and lengthens (increases tension of) the true vocal folds to increase the pitch of the voice o Innervation: external branch of the • Follow the internal laryngeal nerve and superior laryngeal artery through the thyrohyoid membrane into the piriform recess of the larynx

B. From the posterior view of the larynx, identify (Dissector p. 304, 305; Fig. 7.85, 7.86) • Piriform recess, aryepiglottic folds, and aditus or entrance to larynx • Lamina of the cricoid cartilage and position of the arytenoid cartilages sitting on the superior border of the cricoid • Carefully dissect away the mucous membrane of the piriform recess and identify the internal branch of the superior laryngeal nerve and the superior laryngeal artery

32 • Remove mucosa overlying the lamina of the cricoid cartilage and identify the posterior : o Medial attachment: posterior surface of cricoid lamina o Lateral attachment: muscular process of arytenoid cartilage o Action: rotates the arytenoid cartilages laterally so as to Abduct the true vocal folds (only muscle that does this) o Innervation: recurrent (inferior) laryngeal nerve • Remove mucosa overlying the arytenoid cartilages and identify the transverse : o Located between the posterior surfaces of the arytenoids o Action: slides arytenoid cartilages together so as to ADduct the true vocal folds o Innervation: recurrent laryngeal nerve

On one side, identify the cricothyroid joint (a synovial joint) and observe the recurrent laryngeal nerve passing posterior to this joint to enter the larynx. At this point its name changes to inferior laryngeal nerve (Dissector p. 305, Fig. 7.86). (Review the origins of the right and left recurrent laryngeal nerves and their ascent within tracheoesophageal grooves to the larynx). Divide the cricothyroid joint using a scalpel. Anteriorly, cut the thyrohyoid membrane along the superior border of the thyroid cartilage and cut through the lamina of the thyroid cartilage just lateral to the midline. Reflect the lamina inferiorly (should be hinged by the cricothyroid muscle) • Now, identify the lateral cricoarytenoid muscle (the antagonist to the PCA): o Anterior attachment: superior surface of cricoid arch o Posterior attachment: muscular process of arytenoid cartilage o Action: causes arytenoid cartilages to rotate medially so as to ADduct the true vocal folds o Innervation: recurrent laryngeal nerve • Thyroarytenoid muscle – located superior to the lateral cricoarytenoid muscle o Anterior attachment: inner surface of the thyroid cartilage o Posterior attachment: anterior surface of the arytenoid cartilage o Action: causes arytenoid cartilages to tilt forward, relaxing the vocal folds and lowering the pitch of the voice o Innervation: recurrent laryngeal nerve

Additional observations: • Examine the epiglottis. It attaches via short ligaments to both the internal surface of the thyroid cartilage and to the body of the hyoid bone, as well as, to the root of the tongue via glossoepiglottic folds. • Observe the vocal folds from a superior view. The interval (space/cleft) between the folds is the rima glottidis. The glottis is defined as the rima glottidis plus the right and left vocal folds.

33 C. Interior of the larynx (Dissector p. 306, Fig. 7.87) In the midline, make a sagittal cut that passes between the arytenoid cartilages and divides the lamina of the cricoid. Open this up to reveal: • Vestibular folds (“false vocal folds”) – located superior to the vocal folds and their free border is rounded and bulky • Vocal folds (“true vocal folds”) – located below the vestibular folds. The mucous membrane is tightly applied to the underlying vocal ligament. Their free borders are more sharp than the vestibular folds.

There are 3 spaces or cavities within the larynx: • Vestibule – the space superior to the vestibular folds • Ventricle – the space between the vestibular and vocal folds. Often there is a superior extension of this space, known as the saccule • Infraglottic cavity – inferior to the vocal folds

PEER TEACHING GUIDE: 1. Demonstration of the cervical visceral compartment, prevertebral compartment, and retrovisceral/. 2. Demonstration of the muscles (circular and longitudinal) of the pharyngeal wall 3. Demonstration of the sympathetic trunk, cervical sympathetic ganglia (especially superior), and internal carotid nerve. 4. Demonstration of the internal jugular vein, internal carotid artery, and CNs IX, X, XI, and XII leaving the base of the skull. 5. Demonstration of the 3 parts of the pharynx (nasopharynx, oropharynx, laryngopharynx) and associated structures related to each. 6. Demonstration of the muscles of the inner pharyngeal wall. 7. Demonstration of the muscles of the soft palate and the nerve and blood supply to the hard and soft palate. 8. Demonstration of the principal cartilages, membranes, and synovial joints of the larynx. 9. Demonstration of the principal intrinsic muscles of the larynx. 10. Demonstration of the internal, external, and recurrent laryngeal nerves. 11. Demonstration of the vestibular and vocal folds, rima glottidis, and 3 cavities within the larynx.

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