Download D23-1 UNIT 23. DISSECTION: PHARYNX AND LARYNX

UNIT 23. DISSECTION:
PHARYNX AND LARYNX
STRUCTURES TO IDENTIFY:
Nasopharynx
Opening for the auditory tube
Torus tubaris
Salpingopharyngeal fold and muscle
Pharyngeal tonsil
Oropharynx
Palatoglossal fold and muscle
Palatopharyngeal fold and muscle
Palatine tonsils
Soft palate and uvula
Laryngopharynx
Pharyngeal constrictor mm.
Superior
Middle
Inferior
Stylopharyngeus m.
Aryepiglottic fold
Vestibular folds
Glottis
Ventricle of the larynx
Superior laryngeal a.
Glossopharyngeal n.
Vagus n.
Inferior ganglion of vagus n.
Spinal accessory n.
Hypoglossal n.
Larynx
Epiglottis
Thyroid cartilage
Cricoid cartilage
Arytenoid cartilage
Cricothryroid m.
Posterior cricothyroid m.
Superior laryngeal n.
External branch
Internal branch
Inferior laryngeal (recurrent) n.
Vestibule
True vocal folds (vocal ligaments)
Rima glottis
Sacula
Inferior laryngeal a.
DISSECTION INSTRUCTIONS:
1. In this dissection, a considerable portion of the skull will be reflected forward with
the cervical viscera (pharynx, esophagus, larynx, trachea, etc) to expose the pharynx
from behind. In addition, you will be able to expose and study the origins and
courses of certain cranial nerves, which have been hidden until this time. Remove the
dura from the posterior cranial fossa.
2. Step 1 (Fig. D23-1) Insert your fingers posterior to the sternocleidomastoid muscle,
vagus nerve, internal jugular vein, carotid arteries and pharynx, and anterior to the
prevertebral muscles and vertebral column. Separation of structures must be done
from each side so the space is open. Now push your fingers superiorly and extend the
separation to the base of the skull. Palpate the pharyngeal tubercle of the occipital
bone and the anterior tubercle of the atlas. (Plates 35, 60, 63; 8.1, 8.36).
3. Step 2 (D23-2) Use a mallet, chisel and saw to make an opening through the floor of
the cranial cavity into the retropharyngeal space. Using your chisel and hammer,
chisel an opening approximately 1/2 inch in front of the foramen magnum; continue
D23-1
this openings laterally and posteriorly (along both sides of the foramen magnum)
between the jugular foramen and the hypoglossal canal. With the saw, extend the cut
(on both sides) all the way through the occipital bone posterior to the mastoid
process.
Step 1
Fig. D23-1
Step 2
Fig. D23-2
4. Clean and identify the structures at the base of the skull. First note the internal jugular
vein at the base of the skull (N. 69 - 71, 73, 76; G. 8.23). Find the spinal accessory
nerve at its entrance into the sternocleidomstoid muscle and trace it proximally
toward the jugular foramen. Note the internal jugular vein is anterior to the spinal
accessory nerve. Identify the superior cervical ganglion of the cervical sympathetic
chain. Find the vagus n. and identify its inferior (nodose) ganglion. The superior
(jugular) ganglion of the vagus nerve is hidden superiorly and need not be identified.
Trace the superior laryngeal nerve from its origin from the vagus; observe its passage
medially and posteriorly to the two carotid arteries. It then divides into internal and
external laryngeal branches. Trace the hypoglossal nerve from its emergence from
the hypoglossal canal, noting that this nerve passes lateral and anterior to both of the
carotid arteries. You will observe that the hypoglossal nerve is fused firmly with the
vagus nerve for a short distance. Clean the internal carotid a. (note that it has no
branches in the neck).
5. Clean and identify the three constrictor mm (N. plate 67-69, 73, 75, 76; G. 8.23, p.
788). Clean and identify the stylopharyngeus m. It arises from the styloid process
D23-2
and reaches the wall of the pharynx at the upper border of the middle constrictor.
Identify the glossopharyngeal n. traveling on the posterior surface of the
stylopharyngeus.
6. Divide the head using your saw to make a midsagittal cut through the nasal cavity and
the hard palate. Use your scalpel to finish the cut through the soft palate. Do NOT
cut through the tongue.
7. Open the pharynx by making a transverse incision in its posterior wall just below the
base of the skull and a longitudinal incision along the median raphe. Study and
identify the structures of the interior of the pharynx (N. plate 66; G. 8.24). Identify
the posterior aspect of the larynx.
8. Clean the mucosa from the posterior aspect of the larynx to expose the posterior
cricoarytenoid m. (N. 67, 78; G. 8.24B, p. 802). On the anterior aspect of the larynx
identify the cricothyroid muscle ( N. 29, 71, 78; G. 8.13, 8.15, 8.16, 8.23C). Identify
the cartilages of the larynx (N. 77, 78; G. 8.28). Clean and identify the nerves of the
larynx (N. 71, 80; G. 8.29). Split the cricoid cartilage posteriorly in the midline and
identify the structures on the internal surface of the larynx (N. plate 63, 65, 78,; G.
8.30, 8.31B).
D23-3
D23-4