TBL27 - Pharynx

Question 1

What is the terminal end of the pharyngeal gut demarcated by? Where does the pharyngeal gut extend cranially from and to? What does the oropharyngeal membrane separate the endoderm-lined pharyngeal gut from?

Answer 1

1) The terminal end of the pharyngeal gut is demarcated by the lung bud
2) The pharyngeal gut extends cranially from the lung bud to the oropharyngeal membrane
3) The oropharyngeal membrane (not labeled) separates the endoderm-lined pharyngeal gut from the ectoderm-lined stomodeum, the primitive oral cavity

Question 2

What does degeneration of the oropharyngeal membrane establish continuity with? What is the fauces (throat) located between and what is it bounded by superiorly, inferiorly, and laterally?

Answer 2

1) Degeneration of the oropharyngeal membrane establishes continuity of the oropharynx with the oral cavity
2) The fauces (throat), the space between the oral cavity and oropharynx, is bounded superiorly by the soft palate, inferiorly by the root of the tongue, and laterally by the palatoglossal and palatopharyngeal folds

Question 3

What is the nasal cavity continuous with posteriorly and what is this structure incompletely separated from? What is the oropharynx continuous with distally, where is this structure in relation to the larynx, and what other structure does it join?

Answer 3

1) The nasal cavity is continuous posteriorly with the nasopharynx that is incompletely separated from the oropharynx
2) The oropharynx is continuous distally with the laryngopharynx, which is posterior to the larynx and joins the esophagus

Question 4

What does bisection of the posterior pharyngeal wall produce? What can the bilateral mucosa-lined piriform recesses in the laryngopharynx do?

Answer 4

1) Bisection of the posterior pharyngeal wall produces three pharyngeal segments
2) The bilateral mucosa-lined piriform recesses in the laryngopharynx can entrap swallowed objects

Question 5

What two arches is the tonsillar fossa located between? What is different in children and adults in regards to the palatine tonsil?

Answer 5

1) The tonsillar fossa is located between the palatoglossal and palatopharyngeal arches
2) The palatine tonsil fills the fossa in children but only small tonsillar remnants remain in adults

Question 6

What does invagination of the nonkeratinized stratified squamous epithelium of the oropharynx at the tonsillar fossa form and what function does this serve? What are tonsils and when do they form?

Answer 6

1) The nonkeratinized stratified squamous epithelium of the oropharynx is invaginated at the tonsillar fossa to form tonsillar crypts (arrows) that increase mucosal surface area covering the tonsil
2) Tonsils are aggregates of lymphoid nodules that form after the proliferation of activated lymphocytes in response to ingested pathogens

Question 7

What does the orifice of the pharyngotympanic (aka auditory) tube connect the nasopharynx with? Superior to the bony portion or torus of the auditory tube, what does the pharyngeal recess open onto and where?

Answer 7

1) The orifice of the pharyngotympanic (aka auditory) tube connects the nasopharynx with the middle ear (to be studied later)
2) Superior to the bony portion or torus of the auditory tube (remainder of the tube is cartilaginous), the pharyngeal recess opens onto the pharyngeal tonsil (aka adenoids) in the mucosa of the posterior wall of the nasopharynx

Question 8

What are the symptoms of palatine tonsillitis and when is tonsillectomy advised?

Answer 8

1) Sore throat (painful discomfort in the throat) and fever are symptoms
2) A tonsillectomy is advised only when swallowing and
breathing are compromised or when repeated episodes occur in a year

Question 9

What is adenoiditis and why can it necessitate mouth breathing? How can adenoiditis result in otitis media?

Answer 9

1) Inflammation of the pharyngeal tonsils (adenoids) is called adenoiditis, which can obstruct the passage of air from the nasal cavities through the choanae into the nasopharynx, making mouth breathing necessary
2) Infection spreading from the nasopharynx to the middle ear causes otitis media (middle ear infection), which may produce temporary or permanent hearing loss

Question 10

What three tonsils form an incomplete tonsillar ring around the lumen of the pharynx?

Answer 10

The lingual tonsil of the posterior tongue, the palatine tonsils, and the pharyngeal tonsil form an incomplete tonsillar ring around the lumen of the pharynx

Question 11

Where does lymph from the tonsillar ring drain into and what are these lymph nodes a part of?

Answer 11

Lymph from the tonsillar ring drains into the jugulodigastric (aka tonsillar) lymph nodes, which are part of the deep cervical nodes associated with the IJV

Question 12

Where does the salphingopharyngeal fold descend from and into? What is the fold formed by and what is this muscular sheet posterior to?

Answer 12

1) The salphingopharyngeal fold descends from the torus of the auditory tube into the oropharynx
2) The fold is formed by the salpingopharyngeus muscle, the thin unlabeled muscular sheet posterior to the palatopharyngeus muscle to which it blends

Question 13

What three muscles form the inner longitudinal muscle layer of the pharyngeal wall? What three parts does the outer circular muscle layer consist of? Where does the superior constrictor reside in and where do the middle and inferior constrictors reside in?

Answer 13

1) The salpingopharyngeus and palatopharyngeus join the stylopharyngeus muscle to form the inner longitudinal muscle layer of the pharyngeal wall
2) The outer circular muscle layer consists of the superior, middle, and inferior pharyngeal constrictors
3) The superior constrictor resides in the naso- and oropharynx, and the middle and inferior constrictors reside in the laryngopharynx

Question 14

Summarize muscular contributions to the three serial stages of swallowing.

Answer 14

Stage 1: voluntary; the bolus is compressed against the palate and pushed from the mouth into the oropharynx, mainly by movements of the muscles of the tongue and soft palate
Stage 2: involuntary and rapid; the soft palate is elevated, sealing off the nasopharynx from the oropharynx and laryngopharynx. The pharynx widens and shortens to receive the bolus of food as the suprahyoid muscles and longitudinal pharyngeal muscles contract, elevating the larynx
Stage 3: involuntary; sequential contraction of all three pharyngeal constrictor muscles creates a peristaltic ridge that forces the food bolus inferiorly into the esophagus

Question 15

Where do CN IX and CN X exit the cranial cavity? What two pharyngeal arches is CN X derived from? What are muscles of the pharyngeal wall derivatives of and what kind of innervation do these muscles receive from the vagus nerve?

Answer 15

1) CN IX and CN X exit the cranial cavity via the jugular foramen in the cranial base
2) CN X is the nerve of the 4th and 6th pharyngeal arches
3) Like the muscles of the soft palate, muscles of the pharyngeal wall (except the stylopharyngeus) are derivatives of the 4th and 6th arches; thus, the muscles receive somatic motor fibers from the vagus nerve

Question 16

What cranial nerve supplies the 3rd pharyngeal arch? What do myoblasts of the 3rd pharyngeal arch form and where does this muscle receive somatic motor fibers from?

Answer 16

1) CN IX supplies the 3rd pharyngeal arch
2) Myoblasts of the 3rd arch form the stylopharyngeus muscle; thus, the muscle receives somatic motor fibers from the glossopharyngeal nerve

Question 17

What sensations do somatic sensory fibers of CN IX convey from the pharyngeal mucosa to the brain? What does CN IX also provide somatic sensory fibers to?

Answer 17

1) Somatic sensory fibers of CN IX convey sensations of touch, pain, and temperature from the pharyngeal mucosa to the brain
2) CN IX also provides somatic sensory fibers to the posterior tongue

Question 18

What forms the pharyngeal nerve plexus? How many sensory ganglia is CN IX made up of? What type of sensations do these ganglia convey and where do they convey them from and to?

Answer 18

1) Motor fibers of CN X and motor and sensory fibers of CN IX form the pharyngeal nerve plexus
2) CN IX is made up of two sensory ganglia
3) One ganglion conveys somatic sensations from the pharyngeal mucosa and posterior tongue to the brain
4) The other ganglion conveys taste sensations from the posterior tongue to the brain

Question 19

What are the afferent and efferent limbs of the gag reflex?

Answer 19

1) CN IX and CN X are responsible for the muscular contraction of each side of the pharynx
2) Glossopharyngeal branches provide the afferent limb of the gag reflex