0428 - Oral cavity and tongue - CS

Question 1

1a. Describe the boundaries of the oral cavity

Answer 1

Roof - palate (hard and soft)

Floor - muscular diaphragm (mylohyoid muscle) attached to the mandible and hyoid bone (and largely covered by the tongue

Anterior - teeth (in front of teeth is ‘vestibule’)

Laterally - buccinator muscles (anteriorly) and faucial arches (posterio-lateral)

“Back door” - faucial arches open posteriorly at the fauces

Question 2

1c. Describe surface features of the oral cavity

Answer 2

• Hard palate - thin bony plate of the skull, in roof of the mouth. Spans the arch formed by the upper teeth
• Soft palate - a thin layer of CT covered w mucous membrane
• Uvula - part of soft palate. Hangs down. Comes into contact w food bolus and sets off swallowing reflex
• Palatine tonsils - the ‘bulgy bit’ between the anterior faucial arch and the posterior faucial arch
• Posterior faucial arch - also called the palatopharangeal arch (because it’s defined by the edge of the palatopharangeus muscle which goes from the soft palate to the anteriolateral wall of the pharynx)
• Anterior faucial arch - also called the palatoglossal arch (because defined by the edge of the palatoglossus muscle)
• Fauces - posterior opening

Question 3

1e. Describe the surface features of the tongue

Answer 3

• Posterior ⅓ faces posteriorly into the oropharynx and is covered in tonsillar structures - ‘lingual tonsils’
• Anterior ⅔ is within the oral cavity. Has most of the taste buds

Comprises: Rough surface of the tongue is due to papillae (contain sensory receptors for taste and mechano-reception)

(Taste receptors are also present on the soft palate)

Under the tongue is the frenulum (flap of skin running anterior-posteriorly, pulled taught when you left up your tongue)

Ducts of the submandibular and sublingual (salivary glands) open under the tongue

Question 4

2. Describe in general terms, the major features of the dentition

Answer 4

• Enamal outer surface
• Dentin - under the enamel
• Pulp cavity - running in between layers of dentin, space in which branches of nerves and blood vessels run through to supply the dentin (not the enamel)

Question 5

3. Generally discuss the intrinsic muscles of the tongue

Answer 5

Intrinsic muscles - remain entirely within the tongue - no external attachments. Fibres are arranged in x-y-z planes to effect changes of shape of the tongue needed for speech, chewing

Question 6

3. List the four external muscles of the tongue and their functions

Answer 6

Tongue is a muscular structure attached to the mandible and hyoid bone

Extrinsic muscles:

1. Genioglossus - biggest. Fan shaped. Protrudes and depresses the tongue
2. Styloglossus - elevates the posterior end of tongue (eg in swallowing)
3. Hyoglossus - depresses the tongue
4. Palatoglossus - elevates the posterior end (eg in swallowing)

Question 7

Which cranial nerve supplies the intrinsic muscles of the tongue?

Answer 7

Hypoglossal (XII)

Question 8

Which cranial nerves supply the extrinsic muscles of the tongue?

Answer 8

all XII EXCEPT palatoglossus (cranial XI carried in X)

Question 9

4. Describe the attachments, actions and nerve supply of muscles comprising the floor of the mouth (suprahyoid muscles)

Answer 9

The “Suprahyoid group”

1. Mylohyoid m (“forms a sling”) - tenses floor of mouth, supports weight of tongue
2. Geniohyoid m (above mylohyoid) - draws hyoid bone forward
3. Stylohyoid m (pierced by digastric) - elevates the hyoid, draws it posteriorly
4. Digastric m (“2 bellies”) - elevates the hyoid, tenses the floor of the mouth

All innervated by V3 and VII EXCEPT geniohyoid (which is innervated by C1 hitchhiking via XII)

Question 10

4b. How is the tongue anchored in the mouth?

Answer 10

Tongue posteriorly anchored into the hyoid bone and soft palate and anteriorly to the mandible through external muscles of the tongue:

• genioglossus muscle (‘root’ of the tongue) and mylohyoid m both and attach to the mandible and hyoid
• styloglossus m - attach the tongue to the styloid processes of temporal bone
• hyoglossus - attaches the tongue to the hyoid
• palatoglossus - attaches tongue to soft palate

Tongue tethered anteriorly by the frenum

Question 11

4c. Which muscles control movements of the tongue?

Answer 11

Changing of shape of tongue for speaking and chewing- internal tongue muscles

Protruding the tongue - genioglossus

Depressing the tongue - genioglossus, hyoglossus

Drawing the tongue backwards (as in swallowing) - styloglossus

Elevating posterior end of the tongue (as in swallowing) - styloglossus, palatoglossus

Question 12

5. Describe the sensory innervation of the tongue, palate and epiglottal region

Answer 12

Ant 2/3 - V3 (touch), VII (taste)

Post 1/3 - IX (touch), IX (taste)

Epiglottis & vallecula - X (touch), X (taste)

Soft palate - V2 (touch), IX (taste)

Question 13

6d. Describe the sensory and secretomotor nerves of the parotid gland and the paths taken by the nerves involved

Answer 13

Parotid gland innervated by IX (glossopharangeal) which gets there by 1st joining with the V trigeminal nerve, then branching off as the auriculotemporal nerve to supply the parotid gland

VII nerve passes through but does not innervate the parotid gland

Question 14

6c. Describe the sensory and secretomotor nerves of the sublingual and submandibular salivary glands and the paths taken by the nerves involved

Answer 14

Sublingual and submandibular glands innervated by:

1. Occulomotor nerve, V3 lingual branch (pain fibres)
2. Facial nerve VII (both parasympathetic, secretomotor) via corda timpini branch (which comes via the tympanic membrane).

Both nerve branches above join together before supplying sublingual and submandibular glands. Parasympathetic fibres branch off, synapse in the submandibular ganglion, then post-ganglionic parasympathetic fibres branch off to supply glands