TBL26 - Oral Cavity

Question 1

What is the oral cavity and when the mouth is closed, what is it fully occupied by? What is the oral vestibule?

Answer 1

1) The oral cavity is the space between the upper and lower teeth and when the mouth is closed, it is fully occupied by the tongue
2) The oral vestibule is the space between the teeth and oral mucosa

Question 2

Where does the root (posterior third) of the tongue attach to? Where is the mobile body (anterior two thirds) of the tongue found between? What forms the lingual tonsil on the dorsum (dorsal surface mucosa) of the posterior tongue?

Answer 2

1) The root (posterior third) of the tongue attaches to the mandibles and hyoid bone
2) The mobile body (anterior two thirds) is between the root and apex (tip) of the tongue
3) Aggregates of lymphoid nodules form the lingual tonsil on the dorsum (dorsal surface mucosa) of the posterior tongue

Question 3

Where does lymph from the apex and lateral portions of the body of the tongue drain into? Where does lymph from the root and central body of the tongue drain into?

Answer 3

1) Lymph from the apex and lateral portions of the body of the tongue drains into the submental and submandibular lymph nodes, respectively
2) Lymph from the root and central body of the tongue drains directly into the deep cervical lymph nodes

Question 4

What do tiny papillae create on the dorsum of the anterior tongue? Where are the V-shaped row of large papillae located?

Answer 4

1) Tiny papillae (ignore folate, filiform and fungiform designations) create a rough texture on the dorsum of the anterior tongue
2) The V-shaped row of large papillae (ignore valate) are near the junction of the root and body of the tongue

Question 5

Where are taste buds embedded in?

Answer 5

Taste buds are embedded in the epithelium of the large papillae

Question 6

Where do taste buds reside near? Name the three cell types that constitute the taste buds.

Answer 6

1) Taste buds reside in epithelia of papillae near the apex of the tongue
2) Taste (gustatory) cells, supporting (sustentacular) cells, & basal cells constitute the taste buds

Question 7

What does the facial nerve course through to reach the stylomastoid foramen? What do peripheral projecting fibers from the ganglion join and direction does it travel to course toward the stylomastoid foramen?

Answer 7

1) The facial nerve courses through the geniculate ganglion to reach the stylomastoid foramen
2) Peripheral projecting fibers from the ganglion join the facial nerve as it makes the 90° turn during its course toward the stylomastoid foramen

Question 8

What arises from the facial nerve before it traverses the stylomastoid foramen? What type of nerve fibers does this structure contain from the geniculate ganglion and facial nerve, respectively?

Answer 8

1) The chorda tympani arises from the facial nerve before it traverses the stylomastoid foramen
2) The chorda tympani contains the peripheral projecting fibers from the geniculate ganglion and presynaptic parasympathetic fibers from the facial nerve

Question 9

What does the chorda tympani pierce to enter the infratemporal fossa and what does it join within the fossa for transport to the anterior tongue? What sensations are transmitted from the anterior tongue by the lingual nerve to the trigeminal ganglion?

Answer 9

1) The chorda tympani pierces the temporal bone to enter the infratemporal fossa where it joins the lingual nerve, a branch of CN V3, for transport to the anterior tongue
2) Touch, pain, and temperature sensations are transmitted from the anterior tongue by the lingual nerve to the trigeminal ganglion

Question 10

Sensory fibers of the chorda tympani convey what sensation from the anterior tongue back to the facial nerve and what does this nerve convey sensory fibers to? What do the presynaptic parasympathetic fibers of the chorda tympani leave in the oral cavity and where do they synapse?

Answer 10

1) Sensory fibers of the chorda tympani convey taste sensations from the anterior tongue back to the facial nerve, which conveys the sensory fibers to the geniculate ganglion
2) The presynaptic parasympathetic fibers of the chorda tympani leave the lingual nerve in the oral cavity to synapse in the submandibular ganglion

Question 11

Where would injury of CN VII have occurred if its somatic motor fibers were severed but its visceral motor and sensory fibers for taste remained intact?

Answer 11

Lesions near the stylomastoid foramen result in loss

of motor function only (i.e., facial paralysis)

Question 12

Where would injury of the facial nerve have occurred if all its functions were lost?

Answer 12

Lesions near the origin of CN VII from the pons of the brain, or proximal to the origin of the greater petrosal nerve (in the region of the geniculate ganglion), result in loss of motor, gustatory (taste), and autonomic functions

Question 13

What nerve fibers innervate the posterior tongue?

Answer 13

Somatic sensory fibers and sensory taste fibers of the glossopharyngeal nerve innervate the posterior tongue (CN IX will be studied later)

Question 14

What does the midline groove overlying the lingual septum separate? Where does the genioglossus muscle extend from and to?

Answer 14

1) The midline groove overlying the lingual septum separates the bilateral extrinsic muscles of the tongue (ignore the intrinsic muscles)
2) The genioglossus muscle extends from the midline of the mandible to the hyoid bone and entire dorsum of the tongue

Question 15

Where does the hyoglossus muscle extend from and to?

Answer 15

The hyoglossus muscle extends from the hyoid bone to the inferolateral aspect of the tongue (ignore the styloglossus muscle)

Question 16

During its course to the oral cavity and anterior tongue, what does CN XII cross? What muscles does the hypoglossal nerve activate to protrude and retract the tongue, respectively?

Answer 16

1) During its course to the oral cavity and anterior tongue, CN XII crosses the external carotid artery
2) The hypoglossal nerve activates the bilateral genioglossus and hyoglossus muscles to protrude and retract the tongue, respectively

Question 17

Why is an exogenous airway inserted into a patient under general anesthesia?

Answer 17

1) When the genioglossus muscle is paralyzed, the tongue has a tendency to fall posteriorly, obstructing the airway and presenting the risk of suffocation
2) Total relaxation of the genioglossus muscles occurs during general anesthesia; therefore, an airway is inserted in an anesthetized person to prevent the tongue from relapsing

Question 18

What is the clinical sign of unilateral hypoglossal nerve injury?

Answer 18

The tongue deviates to the paralyzed side during protrusion because of the action of the unaffected genioglossus muscle on the other side

Question 19

Where do ducts of the sublingual and submandibular salivary glands open onto? What forms the muscular component of the floor and where are these muscles in relation to the genioglossus muscle of the tongue?

Answer 19

1) Ducts of the sublingual and submandibular salivary glands open onto the mucosa of the oral cavity floor
2) The geniohyoid and mylohyoid muscles, which are inferior to the genioglossus muscle of the tongue, form the muscular component of the floor

Question 20

Where do the muscles of the oral cavity floor extend from and to? They are part of the suprahyoid group that collectively has what function? What is another suprahyoid muscle that is two-bellied?

Answer 20

1) The muscles of the oral cavity floor extend from the mandible to the hyoid bone
2) They are part of the suprahyoid group that collectively elevates the hyoid bone and larynx during swallowing
3) The two-bellied digastric muscle is another suprahyoid muscle

Question 21

What generates the nerve to the mylohyoid muscle and what two muscles does this nerve provide motor fibers to? Like the thyrohyoid muscle of the infrahyoid group, what is the geniohyoid muscle innervated by?

Answer 21

1) The inferior alveolar nerve generates the nerve to the mylohyoid that provides motor fibers of CN V3 to the mylohyoid and anterior belly of the digastric muscle
2) Like the thyrohyoid muscle of the infrahyoid group, the geniohyoid muscle is innerved by C1

Question 22

Where does the posterior belly of the digastric muscle extend from? What is immediately anterior to the mastoid process and what does this allow CN VII to innervate?

Answer 22

1) The posterior belly of the digastric extends from the mastoid process of the temporal bone
2) The stylomastoid foramen is immediately anterior to the mastoid process; thus, CN VII innervates the posterior belly of the digastric

Question 23

Where does the sublingual gland reside? Where does the submandibular gland reside in relation to the mandible? Along with the parotid gland, how much saliva do the three pairs of salivary glands produce per day?

Answer 23

1) The sublingual gland resides in the mucosa of the oral cavity floor
2) The submandibular gland resides in the mucosal floor partly medial and partly inferior to the mandible
3) Along with the parotid, the three pairs of salivary glands produce 1L saliva/day

Question 24

What type of fibers do the chorda tympani contain that synapse in the submandibular ganglion and where is this ganglion located? What are postsynaptic fibers of this nerve transported by to reach the submandibular and sublingual glands?

Answer 24

1) The chorda tympani contains presynaptic parasympathetic fibers from CN VII that synapse in the submandibular ganglion, which is located in the mucosa of the floor of the oral cavity
2) Postsynaptic fibers are transported by branches of the lingual artery to the submandibular and sublingual glands

Question 25

What is the soft palate joined to the tongue and pharynx by? What muscles form these arches?

Answer 25

1) The soft palate is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal arches
2) The arches are formed by the slender palatoglossus and palatopharyngeus muscles

Question 26

What muscle actions occur by the palatoglossus, the tensor palatine and levator palatine muscle, and the muscular core of the uvula during swallowing?

Answer 26

During swallowing, the palatoglossus elevates the posterior tongue, the tensor palatine and levator palatine muscles tense and elevate the soft palate, and the uvula is pulled superiorly by its muscular core (the palatopharyngeus muscle contributes to the wall of the pharynx and will be studied later)

Question 27

What nerve supplies the 4th and 6th pharyngeal arches? What are soft palate muscles derived from, what is the only muscle of the soft palate muscles that is not derived from this area and what is it derived from instead?

Answer 27

1) CN X supplies the 4th and 6th pharyngeal arches (5th arch degenerates)
2) The soft palate muscles are derived from myoblasts of the 4th and 6th arches, except the tensor palatine muscle that is derived from myoblasts of the 1st pharyngeal arch

Question 28

Why do the tensor palatine and levator palatine muscles have different innervations?

Answer 28

1) Both of these muscles have different origins
2) Tensor palatine 1st pharyngeal arch
3) Levator palatine 4th + 6th pharyngeal arch

Question 29

What is the most likely unilateral nerve deficit in a patient whose uvula deviates to the left during swallowing?

Answer 29

Right vagus nerve is damaged

Question 30

How do taste buds differ from the olfactory mucosa?

Answer 30

Unlike olfactory receptor cells, which are primary receptor neurons in olfactory mucosa, taste cells are epithelial cells that are contacted by synapses at their basal aspect by afferent nerve fibers