Using the Sectra table, you will identify features of the Pharynx, larynx, and neck. Bolded terms are in the objectives for this lab.
The pharynx, larynx, and neck
“The neck is a region of transition between the head and and the thorax. The major vessels that supply the head and the nerves that innervate the organs within the thorax and abdomen pass through the neck. Portions of several systems are located in the neck: gastrointestinal system (pharynx and esophagus), respiratory system (larynx and trachea), cardiovascular system (major vessels to the head and upper limbs), central nervous system (spinal cord), and endocrine system (thyroid and parathyroid glands).
[…] The pharynx extends from the base of the skull to the inferior border of the cricoid cartilage (vertebral level C6). The pharynx can be subdivided from superior to inferior as the nasopharynx, oropharynx, and laryngopharynx… The larynx is the entrance to the airway, and it contains the glottis, a valve that serves the dual function of controlling the airway and producing sound during phonation… The larynx is contained in the visceral compartment of the neck with the thyroid gland lateral to it and the pharynx posterior to it.” – Grant’s Dissector 16th ed.
Use the following view to review the cervical vertebrae and hyoid bone:
As you identify and dissect muscles, you should review their origin, insertion, innervation, and action(s). As you identify and dissect neurovascular structures, you should review their pathways.
If you are having trouble highlighting narrow structures (arteries, veins, nerves), you can search for them by selecting the Anatomy tab, typing the name of the structure in the search box, and selecting the sun icon next to the listed structure. You can dissect these structures by selecting the eye icon.
As you highlight a structure, note that the structure will also be highlighted in the multiplanar reconstructed (MPR), or cross-sectional images in the leftmost pane. All structures should be identified on the MPR images. Using three fingers, scroll through the MPR images to understand the three-dimensional relationships between different structures as you work though the lab. Structures that are difficult to identify in the MPR images will have additional links to assist you.
Use the following view to begin your dissection (select this button at any time to start over):
The triangles of the neck
Note that fasica in the neck is not visible on the model. Review your lecture notes to understand their relative positions.
- Dissect the platysma. Identify the external jugular vein superficial to the sternocleidomastoid muscle
- Identify the tributaries of the external jugular vein: the retromandibular vein and posterior auricular vein
- Identify the boundaries of the posterior triangle:
- Anterior: posterior border of sternocleidomastoid muscle
- Posterior: superior border of trapezius muscle
- Inferior: middle one-third of the clavicle
- Superficial (roof): investing layer of deep cervical fascia
- Deep (floor): muscles of the neck covered by prevertebral fascia
- In the posterior triangle, identify the cervical plexus of nerves (only visible on the left side of the model): lesser occipital nerve, great auricular nerve, and supraclavicular nerves. The transverse cervical nerve is absent on the model, identify it on the diagrams below
- In the posterior triangle, identify the accessory nerve (CN XI)
- Dissect the trapezius muscle on both sides
- Identify the boundaries of the anterior triangle:
- Anterior: midline of neck
- Posterior: anterior border of sternocleidomastoid muscle
- Superior: inferior border of mandible
- Superficial (roof): deep cervical fascia
- The anterior jugular veins are anterior to the anterior triangle of the neck, identify them on the diagrams below
Q1: What facial expression is associated with the platysma? (answer)
- Identify the boundaries of the muscular triangle:
- Superolateral: superior belly of omohyoid m. Note that both parts of omohyoid are labeled “inferior belly” on the model. Use the diagrams as a guide
- Inferolateral: anterior border of sternocleidomastoid m.
- Medial: median plane of neck
- Dissect the sternocleidomastoid on the right side to better observe the deeper structures. Leave the left sternocleidomastoid muscle in place until you have finished reviewing the borders of the remaining triangles of the neck
- Identify the infrahyoid muscles: sternohyoid, omohyoid, sternothyroid, and thyrohyoid muscles (you will need to dissect the sternohyoid on the right side to identify some of these muscles) (MPR)
- Dissect the infrahyoid muscles and cricothyroid muscle on the right side to identify the portions of the thyroid cartilage, cricoid cartilage, and thyroid gland visible in the muscular triangle
- Identify the boundaries of the submental triangle:
- Right and left: anterior bellies of the right and left digastric muscles
- Inferior: hyoid bone
- Superficial (roof): investing layer of deep cervical fascia
- Deep (floor): mylohyoid muscle
- Identify the boundaries of the submandibular triangle:
- Superior: inferior border of the mandible
- Anteroinferior: anterior belly of the digastric muscle
- Posteroinferior: posterior belly of the digastric muscle. Note that both bellies of the digastric are labeled “anterior” on the model. Use the diagrams as a guide
- Superficial (roof): investing layer of deep cervical fascia
- Deep (floor): mylohyoid and hyoglossus muscles. You will need to dissect the submandibular gland to observe the hyoglossus
- In the submandibular triangle, identify the stylohyoid muscle, the facial artery and the hypoglossal nerve (CN XII) (MPR)
- Identify the boundaries of the carotid triangle:
- Superior: posterior belly of the digastric muscle
- Inferolateral: anterior border of sternocleidomastoid m. (you may now dissect this muscle on the left side)
- Inferomedial: superior belly of omohyoid m.
- The ansa cervicalis is wrapped around the carotid sheath. Neither structure is visible on the model, identify them on the diagrams below.
- Identify the contents of the carotid sheath: the internal jugular vein, common carotid artery, and vagus nerve (CN X) (MPR)
- Observe the bifurcation of the common carotid artery into the internal carotid artery and external carotid artery
- Dissect the following structures to have a clear view of the branches of the external carotid artery: digastric muscle, stylohyoid muscle, external jugular vein, posterior auricular vein, and retromandibular vein
- On the left side, identify the following branches of the external carotid artery: superior thyroid artery, lingual artery, facial artery, occipital artery, maxillary artery, and superficial temporal artery (MPR)
- The superior laryngeal artery, posterior auricular artery, and ascending pharyngeal artery are not visible on the model. Identify them on the diagrams below
- Identify the branches of the vagus nerve: the superior laryngeal nerve (close to the superior thyroid artery) and recurrent laryngeal nerve (inferior the thyroid gland)
Q2: What are the spinal roots of the ansa cervicalis? Describe the relationship of the ansa cervicalis to the hypoglossal nerve (CN XII). (answer)
Root of the neck and posterior neck
- Dissect the clavicles, and any remaining infrahyoid muscles
- Identify the thoracic duct on the left side, and the right lymphatic duct on the right side (MPR)
- On the right side only, dissect the internal jugular vein. Dissect the right lymphatic duct
- Identify the anterior, middle, and posterior scalene muscles
- Identify the phrenic nerve and subclavian vein anterior to the anterior scalene, and the trunks of the brachial plexus and subclavian artery emerging between the anterior and middle scalene
- Identify the branches of the first part of the subclavian artery: the vertebral artery, internal thoracic artery, and thyrocervical trunk (MPR)
- Identify the branches of the thyrocervical trunk: the inferior thyroid artery, transverse cervical artery, and suprascapular artery
- Dissect the anterior scalene muscle on the right side and identify the costocervical trunk on the second part of the subclavian artery
- The dorsal scapular artery is not visible on the model, identify it on the third part of the subclavian artery using the diagrams below
Q3: What does the phrenic nerve innervate? What are the spinal roots of the brachial plexus? (answer)
- Rotate the model to view the posterior side of the neck, dissect the middle and posterior scalene muscles on the right side
- Identify the longus capitis and longus colli muscles (MPR), then dissect the cervical vertebrae, T1 thoracic vertebra, intervertebral discs, ribs, and (on the right side) the vertebral artery
- Dissect the longus capitis and longus colli on the right side. Use the diagrams below to review the fascia in this region: buccopharyngeal fascia, prevertebral fascia, and alar fascia
- Identify the superior pharyngeal constrictor muscle, middle pharyngeal constrictor muscle, and inferior pharyngeal constrictor muscle
- Dissect the spinal nerves and spinal ganglia on the right side
- Medial to the internal carotid artery on the right side, identify the superior cervical ganglion. Trace the sympathetic trunk inferiorly to identify the middle cervical ganglion and inferior cervical ganglion (MPR)
- Identify the glossopharyngeal nerve (CN IX) near the base of the skull
Q4: Where is the true “danger space” located, and why is it called the danger space? (answer)
The pharynx
Use the following examine the pharynx (select this button at any time to start over):
- Dissect the occipital and temporal bones
- On the posterior side, identify the pharyngeal tonsil (adenoid tonsil) and nasopharynx superior and deep to the superior pharyngeal constrictor muscle. Observe these features in the sagittal MPR plane
- Dissect the superior pharyngeal constrictor and identify the cavity of the oropharynx and the palatine tonsils (MPR)
- The palatoglossal fold is not visible on the model, but you can identify its position based on the palatoglossus muscle
- Dissect the middle and inferior pharyngeal constrictors to identify the cavity of the laryngopharynx and the lumen of the esophagus (MPR)
- Dissect the palatoglossus and the cavites of the oropharynx and laryngeopharynx to identify the epiglottis (MPR)
- Use the MPR images with the diagrams below to identify the following additional structures of the pharynx:
- Nasopharynx: posterior nasal aperture (choana), opening (ostium) of the pharyngotympanic tube (auditory tube, Eustachian tube), torus tubarius, salpingopharyngeal fold, pharyngeal recess
- Oropharynx: palatoglossal fold and palatopharyngeal fold
- Laryngeopharynx: inlet of the larynx and the piriform recess and borders
The Larynx
Use the following examine the larynx (select this button at any time to start over):
- Identify the thyroid gland, on the posterior side you can identify some of the parathyroid glands. Dissect the left and right lobes of the thyroid gland to view and dissect the remaining parathyroid glands
- Identify the cartilages of the larynx: epiglottic cartilage, thyroid cartilage, cricoid cartilage, arytenoid cartilages, and tracheal cartilages
- Use the diagrams below to identify features of the thyroid cartilage: lamina, laryngeal prominence, and superior and inferior horn
- Identify the thyrohyoid membrane (MPR)
- Rotate the model to view the anterior side and identify the cricothyroid muscle. On the left side identify the superior laryngeal nerve
- The superior laryngeal nerve splits into external branch and internal branch. Identify them on the diagrams below
- Rotate back to the posterior side and identify the recurrent laryngeal nerves. This nerve becomes the inferior laryngeal nerve when it crosses the cricothyroid joint, use the diagrams below to understand this relationship
- Identify the posterior cricoarytenoid muscle and (transverse) arytenoid muscle (MPR)
- Dissect the thyroid cartilage and cricothyroid muscle to identify the lateral cricoarytenoid muscle
- Rotate the model to view the larynx from a superior perspective and dissect the epiglottic cartilage, you should be able to identify the vocal folds (true vocal folds). The area medial to these folds (not selectable on the model) is the glottis. The vocal folds and glottis together form the rima glottidis (MPR)
- Use the MPR images with the diagrams below to identify the following structures of the larynx: vestibule, ventricle, infraglottic cavity, and vestibular fold (false vocal fold)
Q5: Describe how the path of the left recurrent laryngeal nerve is different from the right recurrent laryngeal nerve. What are the clinical implications? (answer)
End of Sectra activity
Answers to activity questions
Below are answers to questions asked during the activity. Clicking the ‘back to lab’ link below each answer will take you back to the question (you may need to scroll up a little to view the question again).
Q1: What facial expression is associated with the platysma?
- You tense the platysma when making an ‘eek’ expression (bottom left pane of the figure)
Q2: What are the spinal roots of the ansa cervicalis? Describe the relationship of the ansa cervicalis to the hypoglossal nerve (CN XII).
- Superior root of ansa cervicalis: C1-C2
- Inferior root of ansa cervicalis: C2-C3
- The superior of root travels with the hypoglossal nerve – it is supported by this nerve but fibers do not cross from one to the other.
Q3: What does the phrenic nerve innervate? What are the spinal roots of the brachial plexus?
- The phrenic nerve innervates the diaphragm
- The spinal roots of the brachial plexus are C5-T1
Q4: Where is the true “danger space” located, and why is it called the danger space?
- The danger space is the potential space between the alar fascia and the prevertebral fascia (it is not the same as the retropharyngeal space, which is between the alar fascia and buccopharyngeal fascia)
- The danger space runs from the base of the skull to the top of the diaphragm, allowing infection to easily travel to the thorax
Q5: Describe how the path of the left recurrent laryngeal nerve is different from the right recurrent laryngeal nerve. What are the clinical implications?
- The right recurrent laryngeal nerve passes anterior to and loops around the right subclavian artery before traveling superiorly to the larynx. The left recurrent laryngeal nerve travels more inferiorly, looping around the arch of the aorta before traveling between the trachea and esophagus to reach the larynx.
- Both nerves can be affected by diagnostic procedures in the superior mediastinum. The left recurrent laryngeal nerve can also be affected by brochogenic or esophageal carcinomas. It can also be affected by aneurysm of the arch of the aorta – a hoarse voice is one of the symptoms of this pathology.