L46. Oral Cavity and Oropharynx

Question 1

What forms the roof of the mouth?

Answer 1

Part of the roof is formed by the superior alveolar arch

The HARD PALATE (which is formed by palatine process of the maxilla and also by the horiztonal process of the palatine bone

and

Posteriorly, the SOFT PALATE and uvula

Question 2

The alveolar arches also have another name based on what anchors into them. What is this name and function?

Answer 2

The dental arches

They house the teeth

Question 3

What is the floor of the oral cavity made up of?

Answer 3

It is formed mainly by a diaphrgam muscle bridging the rami of the mandible (ie. closing the hole in the inferior part of the mandible)

Question 4

What are the main muscles that make up the floor of the oral cavity. Describe their origins and insertions and draw their arrangement

Answer 4

• The main muscle is the mylohyoid bone that connects the internal surface of the mandible to the superior surface of the hyoid bone
• The digastic muscles sit anteriorly to the mylohyoid bone and consists of two muscular bellies united by an intermediate rounded tendon. They run from the mandible all the way back to the temporal bone.
• The geniohyoid muscle lies internal to the mylohyoid bone, running in the midline from the geniotubercles of the mandible to the hyoid bone

Question 5

Describe the major divisions of the tongue

Answer 5

The tongue is divided roughly into 2 main divisions: anterior 2/3rds and the posterior 1/3rd

The delination between them is by a V shaped groove called the sulcus terminalis which has its apex pointing posteriorly

Question 6

What is the depression at the apex of the sulcus terminalis of the tongue called? What is the function?

Answer 6

The foramen caecum is an embryonlogical remnant of where the thyroglossal duct developed before it descended into the neck as the thyroid gland. Once the thyroid develops, the duct closes leaving this depression.

Question 7

Describe the posterior third of the tongue

Answer 7

It is very nodular as it contains a lot of lymphoid tissue called the lingual tonsil (group of tissues) directly under the mucosa of the tongue

Question 8

What are the 4 main papillae on the surface of the tongue, describe their location

Answer 8

1. Fungiform papillae: over the anterior part of the tongue (mainly the outskirts)
2. Vallate papillae (also called circumvalate): line the anterior aspect of the sulcus terminalis
3. Foliate papillae: Lining the posteriolateral aspect next to the sulcus terminalis
4. Filliform papillae: over the medial part of the anterior 2/3rds of the tongue

Question 9

Describe the shape and function of the 4 different papillae on the surface of the tongue

Answer 9

Name

Shape

Function

Vallate

Large and Round (only 10-14 per person)

Contain taste buds

Fungiform

Look like mushrooms, small and red

Contain taste buds

Foliate

Short vertical folds; Ridges and Grooves

Contain taste buds

Filliform

Small, pointy projections

Roughens the tongue to help grip the food bolus

Question 10

What is the significance of the papillae in terms of function?

Answer 10

They contain the taste buds, specialised sensory cells that sit deep in the walls of the papillae

Question 11

Are taste buds present in all the types of papillae of the tongue?

Answer 11

No

Taste buds are only present in circumvalate, fungiform, and foliate papillae (and soft palate) but not filiform papillae.

Question 12

What is the main function of the extrinsic muscles of the tongue as a group?

Answer 12

They alter the position of the tongue

Question 13

What are the 4 main external muscles of the tongue? Describe their attachments and their function

Answer 13

Name

Attachment

Function

Hypoglossus

Attaches from the base of the tongue to the hyoid bone

Contraction depresses the tongue into the oral cavity

Palatoglossues

Attaches to the soft palate

Contraction elevates the tongue

Styloglossus

Attaches to the styloid processes of the temporal bone

Contraction retracts the tongue (pulls it into the mouth)

Genioglossus

Attaches to the genial tubercle in the midline of the mandible

Contraction pulls the tongue forward and out of the mouth (protraction)

Question 14

Describe the innervation of the external muscles of the tongue

Answer 14

All of the muscles are innervated by CN XII - hypoglossal nerve (except palatoglossus which is innervated by the vagus)

Question 15

Describe what damage to the hypoglossal nerve (a LMN lesion on one side) would appear when asking the patient to stick their tongue out

Answer 15

The tongue deviates to the side of lesion

This is because normally sticking out the tongue (genioglossus muscle) is achieved by pushing the two halves of the muscle against each other to achieve protraction. But if one side has lost innervation then the working side is able to push against it unopposed so the tongue deviates to the side of the lesion.

Question 16

What is the function of the intrinsic muscles of the tongue as a whole?

Answer 16

They contract against each other to alter the shape of the tongue

Question 17

What are the intrinsic muscles of the tongue?

Answer 17

They are all named by the projection/orientation of the muscle fibres.

They all have attachments within the tongue and form the body of the tongue.

Question 18

What innervates the intrinsic muscles of the tongue?

Answer 18

They are all innervated by the CN XII

Question 19

Describe the somatic motor innervation to the tongue

Answer 19

The whole tongue is innervated by the hypoglossal nerve, except the palatoglossus muscle (innervated by a branch of vagus)

Question 20

Describe the somatic sensory innervation to the tongue

Answer 20

• The posterior third recieves almost all sensory innervation by the glossopharyngeal nerve IX (taste and general somatic sensation)
• Anterior 2/3rds from the lingual nerve; a branch of the mandibular division of the trigeminal nerve (V3)

Question 21

Describe the special sensory innervation to the tongue (taste)

Answer 21

• Posterior third recieves almost all sensory innervation by the glossopharyngeal nerve
• Anterior 2/3rds: taste mediated by the chordae tympani, a branch from the facial nerve and has the tortuous course through the middle ear

Question 22

What is important to note about teeth and pain?

Answer 22

Dental pain can refer to lots of other parts of the head because of shared nerve supply and vice versa.

Question 23

What are the teeth?

Answer 23

From medial to lateral:

1. Two Incisors
2. One Canine
3. Two Premolars
4. Three Molars

Question 24

Each type of tooth has a shape adapted to function, describe these for each tooth

Answer 24

Tooth

Shape

Function

Incisors

Flat, sharp surface

Cuts through food

Canines

Pointy edge

Anchors onto food and tears it out

Pre-molars/molars

Flat cusps

Grinding and macerating food

Question 25

Where are the teeth embedded?

Answer 25

In the superior and inferior alveolar arches

Question 26

What is the significance of the wisdom teeth?

Answer 26

Adult teeth erupt in certain ages, but don’t do so completely sequentially. The Wisdom teeth are the third molars (often the last to erupt). By this stage, there is not much room at the back of the arches for the wisdom teeth, so they often grow into the 2nd molars and impact on them.

Question 27

Describe the nerve supply to the teeth

Answer 27

Upper teeth are supplied by the maxillary division of the trigeminal V2 and the lower teeth from the mandibular division V3

Question 28

Describe what kind of referred pain can occur in the upper teeth and in the lower teeth

Answer 28

Upper teeth: Dental pain can be referred to other branches of the maxillary nerve such as the maxillary sinus Lower teeth: From the auriculotemporal nerve (part of the external auditory meatus and temperomandibular joint, dental pain can refer to the ear)

Question 29

Describe the arterial supply to the teeth

Answer 29

The teeth are supplied by branches from the **external carotid artery**

Question 30

What is the main function of the salivary glands? ## Footnote List the three salivary glands

Answer 30

They **produce saliva**, which keeps the mouth and other parts of the digestive system **moist**. It also helps **break down carbohydrates** and **lubricates the passage** of food. It also has some **antimicrobial properties** 1. Parotid gland 2. Submandibular gland 3. Sublingual gland

Question 31

Describe the location of the parotid gland, the duct and its opening

Answer 31

* It sits anterior to the external auditory meatus. * The duct is superficial to the masseter muscle * The duct opens opposite the upper 2nd molar tooth.

Question 32

Describe the location of the submandibular gland, the duct and its opening

Answer 32

* It has 2 parts formbed by the wrapping of the gland around the free edge of the mylohyoid muscle: Inside the oral cavity and outside * The duct runs forward, perices the subligual gland and runs into the subligual papilla * The ducts open just lateral to the lingual frenulum

Question 33

Describe the location of the sublingual gland, the duct and its opening

Answer 33

* Runs along the floor of the mouth lateral to the tongue * It contains many ducts and openings directly into the mucosa info the floor of the mouth lateral to the tongue

Question 34

What are the major structures in the floor of the mouth?

Answer 34

Question 35

The floor of the mouth (mucosa under the tongue) is highly vascular. What implication does this have?

Answer 35

Very rapid drug absorption from the tongue

Question 36

Where does the oral cavity end?

Answer 36

By definition, it ends at the back of the dental/alveolar arches (boundary between oral cavity and oropharynx)

Question 37

What forms the following of the oropharynx... * Roof * Floor * Lateral walls

Answer 37

* Roof largely formbed by the soft palate * Floor by posterior third of the tongue and epiglottis. * Lateral walls contain the tonsils and related structures and mucosal arches

Question 38

Describe the arches of the oropharynx

Answer 38

They are formed by the mucosal folds of the muscles of the oral cavity and pharynx. * **Palatoglossal arch** anteriorly runs from the soft palate to the tongue. Formed by the underlying palatoglossal muscle. * **Palatopharyngeal arch** posteriorly runs from the soft palate to the pharynx formed by mucosa sitting over the palatopharyngeal muscle.

Question 39

What sits in between the two arches of the oropharynx?

Answer 39

The palatine tonsils

Question 40

What are the tubal tonsils, where are the located?

Answer 40

They are a small group of tonsils sitting over the cartilagenous part of the auditory tube

Question 41

What makes up the soft palate of the oropharynx?

Answer 41

It largely consists of muscle: * **musculus uvulae** (which sits in the midline) connected by the **palatine aponeurosis** connective tissue to the hard palate. * All lined by mucosa.

Question 42

"The soft palate is able to function in **two opposing ways"** ## Footnote What is meant by this statement?

Answer 42

The soft palate is able to: * Seal the nasal cavity during swallowing and coughing and suction actions by folding upwards * Aid sealing the oral cavity to allow unimpeded breathing during chewing by folding downwards

Question 43

What are the 5 muscles that support the structure of the soft palate and make it move? Label them on the following diagram

Answer 43

1. Tensor veli palatini 2. Levator veli palatini 3. Musculus uvulae 4. Palatoglossus 5. Palatopharyngeus

Question 44

What actions do each of the muscles have on the soft palate? What other structure do they move?

Answer 44

Two muscles sit on the superior and lateral aspects of the soft palate and hence **elevate it** * Tensor veli palatini pulls the soft palate up (Cartilagenous auditory tube and surrounding bones eg sphenoid) * Levator veli palatini pulls the the soft palate up (Cartilagenous auditory tube and petrous temporal bone) Midline muscle: musculus uvulae is the muscle that all the others attach to Contraction pulls the soft palate **downwards** * Palatoglossus * Palatopharyngeus They also are involved with the auditory tube above and the pharynx below

Question 45

What is the innervation of the muscles associated with the soft palate

Answer 45

All muscles innervated by pharyngeal branches of Vagus except for tensor veli palatini (CN V)

Question 46

What is Waldeyer's Ring?

Answer 46

Refers to all tonsilar tissue (coronal section has a complete ring of tissue guarding the oral cavity). * Pharyngeal * Tubal * Palatine * Lingual