Oral Cavity

Question 1

The oral cavity (commonly called mouth) represents the first part of the digestive tube, serving as the entrance of the alimentary canal and initiating the digestive process by salivation and propulsion of the alimentary bolus into the pharynx. State other functions of the oral cavity.

Answer 1

1. Secondary respiratory conduit.
2. Site of sound modification for the production of sound.
3. A chemosensory organ.
4. [Diagram: Anatomy of Oral Cavity]

Question 2

State the extents of the oral cavity.

Answer 2

Anteriorly: at the lips (through the oral fissure to the face)
Posteriorly: oropharyngeal isthmus/isthmus of the fauces
[Diagram]

Question 3

The oral cavity is divided into 2 parts by the upper and lower dental arches (formed by the teeth and their bony scaffolding). Name them.

Answer 3

☞ Vestibule of the mouth
☞ Oral cavity proper

Question 4

What forms the:
(a) roof of the oral cavity?
(b) lateral walls of the oral cavity?
(c) floor of the oral cavity?

Answer 4

(a) palate
(b) cheeks
(c) diaphragma oris

Question 5

The vestibule is bound externally by the lips and the cheeks, and internally by the gums and teeth. The entire vestibule is lined by mucous membrane except the teeth. When the mouth is closed, the vestibule communicates on each side with the oral cavity proper through a small gap behind the 3rd molar tooth and ramus of mandible called ______________________.

Answer 5

retromolar region
[Figure 1]
[Figure 2] [Figure 3] [Figure 4]

Question 6

What is the clinical significance of the gap located in the back of the lower vestibule [retromolar space]?

Answer 6

instrumentation during dental procedures

Question 7

Lips
They are musculofibrous folds that surround the oral fissure (aperture). There are the external (skin) and internal (mucous membrane) surfaces of the lips. Click on the image in the Answer section to appreciate some of the parts of the lips.

Answer 7

[Image]

Further notes:
☞ The red hue on the vermillion zone is due to rich vascular bed visible through the thin moist epithelium.
☞ The internal aspect of each lip is connected to the corresponding gum by a median fold of the mucous membrane called frenulum of the lip.

Question 8

List the structures in the lip from superficial to deep.

Answer 8

1. Skin.
2. Superficial fascia.
3. Orbicularis oris muscle.
4. Submucosa containing mucous glands.
5. Mucous membrane.

Question 9

Describe the blood supply and lymphatic drainage of the lips.

Answer 9

Blood Supply
Each lip is supplied by labial branches of facial artery. Each lip has an arterial arch formed by the end-on anastomosis between labial branches of the facial arteries. When this arterial arch is cut, blood spurts from both ends with equal force. The veins correspond to the arteries and drain into the facial vein.

Lymphatics
☞ The lymphatics from the central part of the lower lip drain into submental lymph nodes.
☞ The lymphatics from lateral parts of lower lip and whole of upper lip drain into submandibular lymph nodes.

Question 10

Describe the nerve supply of the lips.

Answer 10

☞ The lips have rich sensory supply from trigeminal nerve.
☞ The upper lip is supplied by labial branches of the infraorbital nerve (a branch of the maxillary division) and lower lip by the mental nerve (a branch of the inferior alveolar nerve, which is a branch of the posterior division of the mandibular division).
☞ The red portions of lip are highly sensitive and represented by a large area in the sensory cortex of cerebral hemisphere.

Question 11

List the 7 layers of the cheek from superficial to deep.

Answer 11

1. Skin.
2. Superficial fascia containing some muscles of facial expression, viz. zygomaticus major, risorius.
3. Buccal pad of fat.
4. Buccopharyngeal fascia.
5. Buccinator muscle between the alveolar processes of both jaws.
6. Submucosa containing buccal (mucus) glands.
7. Mucus membrane.

Further notes:
☞ The last five layers of the cheek are pierced by the parotid duct.
☞ The lymphatics from the cheek drain into the submandibular and preauricular lymph nodes.

Question 12

The gums are composed of fibrous tissue covered with a smooth vascular mucous membrane. They envelop the alveolar processes of the jaws and the necks of the teeth. At the necks of the teeth, the fibrous tissue of gum becomes continuous with the periodontal membrane, which attaches the teeth to their sockets. The gum/gingiva has 3 parts. Name them.

Answer 12

1. Free part (free gingiva), which surrounds the neck of tooth like a collar.
2. Attached part (attached gingiva), which is firmly attached to the alveolar process.
3. Interdental part (interdental gingiva), which is the extension of the attached gingiva between the teeth.
4. [Image]

Question 13

The oral cavity proper has a roof and a floor. Posteriorly the oral cavity communicates with the oropharynx through oropharyngeal isthmus (also called isthmus of fauces). Boundaries of the oropharyngeal isthmus?

Answer 13

Superiorly: Soft palate
Inferiorly: Dorsal surface of the pharyngeal part of tongue
Laterally (on each side): Palatoglossal arches

[Diagram]

Question 14

Necessities of the palatoglossal arches?

Answer 14

The approximation of these arches shuts off the mouth from oropharynx and is essential to deglutition.

Question 15

Click on Answer to view a diagram showing the floor of the oral cavity. Appreciate the lingual frenulum, sublingual papilla and sublingual fold.

Answer 15

[Diagram 1] [Diagram 2]

Further notes:
☞ The sublingual papilla is the opening of the submandibular duct. Where is the parotid papilla located?
☞ Many structures in the oral cavity are termed by their relationship to the tongue, palate, cheeks, and lips. The structures closest to the tongue are termed ‘lingual’. Those closest to the palate are termed ‘palatal’. Those closest to the cheeks are termed ‘buccal’. And those closest to the lips are termed ‘labial’.

Question 16

What is Ludwig’s angina?

Answer 16

Ludwig’s angina is a cellulitis of the floor of the mouth, usually due to infection from a carious molar tooth, causing inflammatory edema of the floor of the mouth. It spreads to the submandibular and submental regions producing diffuse swelling in these regions also. The tongue is pushed upwards due to edema of the floor of the mouth, resulting in difficulty in swallowing.

[Diagram]

Question 17

The paralingual space is found in the floor of the mouth. State its boundaries.

Answer 17

mylohyoid muscle, lateral margin of the tongue, hyoid bone, and oral mucosa

Question 18

State the contents of the paralingual space. What is its clinical significance?

Answer 18

1. Sublingual gland.
2. Lingual nerve.
3. Submandibular duct.
4. Deep lingual vein.
5. Lingual artery.
6. Lymph nodes.

The mylohyoid line divides the floor of the mouth into a submandibular space below and a paralingual space above the line.

[11 minute video: Dissection of Paralingual Space]

Clinical significance: spread of infections to other spaces that it communicates with, tumours affecting structures there, etc.

Question 19

(a) The posterior part of the tongue forms the ________________ wall of the oropharynx.
(b) The tongue is separated from the teeth by a deep ________________ sulcus, which is filled by palatoglossal fold/arch posterior to the last molar tooth.

Answer 19

(a) anterior
(b) alveololingual

Question 20

Features on the oral part of tongue?
Features on the pharyngeal part of tongue?

Answer 20

Features on the oral part of tongue:
1. A median furrow, representing the bilateral origin of the tongue.
2. Large number of papillae.

Features on the pharyngeal part of tongue:
1. A large number of lymphoid follicles, which together constitute the lingual tonsil.
2. A large number of mucus and serous glands.

Note:
The furring or coating of tongue bears no relation to digestive disturbances as generally thought, but is usually due to smoking, respiratory tract infection, fever, or oral infection.

Question 21

Click on Answer to view linked images and diagrams the of topography of the tongue.

Answer 21

[1] [2] [3] [4] [5] [6]

Question 22

The musculature of tongue consists of intrinsic and extrinsic muscles.
List the intrinsic muscles of the tongue, stating the locations and actions.

Answer 22

1. Superior longitudinal
   Location: Beneath the mucous membrane.
   Actions:
   ☞ Shortens the tongue
   ☞ Makes the dorsum concave
2. Inferior longitudinal
   Location: Close to inferior surface between genioglossus and hyoglossus
   Actions:
   ☞ Shortens the tongue
   ☞ Makes the dorsum convex
3. Transverse
   Location: Extends from median septum to the margin
   Action: Makes the tongue narrow and elongated
4. Vertical
   Location: At the border of the anterior part of the tongue
   Action: Make the tongue broad and flattened.
5. [Diagram] [Diagram 2]
6. [3-minute Video]

Question 23

Genioglossus
1. Origin
2. Insertion
3. Action

Answer 23

1. Origin: Superior genial tubercle
2. Insertion:
   ☞ Whole of the tongue (fibres radiate from the tip to the base)
   ☞ Hyoid bone (lowest fibres)
3. Action: Protrusion of tongue
4. [Diagram]

Note: The extrinsic muscles of the tongue of both sides act together for example genioglossus muscle of both sides, etc.

Question 24

Hyoglossus
1. Origin
2. Insertion
3. Actions

Answer 24

1. Origin: greater cornu and adjacent part of the body of hyoid [Diagram: hyoid bone]
2. Insertion: side of tongue (posterior half) between styloglossus laterally and inferior longitudinal muscle medially.
3. Actions:
   ☞ Depresses the sides of the tongue
   ☞ Makes the dorsal surface convex
4. [Diagram]

Question 25

Styloglossus
1. Origin
2. Insertion
3. Action

Answer 25

1. Origin: Tip of styloid process and adjacent part of the stylohyoid ligament
2. Insertion: Side of tongue (whole length), interdigitating posteriorly with the fibres of hyoglossus
3. Action: Draws the side of the tongue upwards and backwards
4. [Diagram]

Question 26

Palatoglossus
1. Origin
2. Insertion
3. Actions

Answer 26

1. Origin: Oral surface (inferior surface) of palatine aponeurosis of palate
2. Insertion: Side of tongue (at the junction of its oral and pharyngeal parts)
3. Actions:
   ☞ Pulls up the root of the tongue
   ☞ Approximates palatoglossal arches to close the oropharyngeal isthmus
4. [Diagram 1] [Diagram 2]

Note:
The right and left palatoglossus muscles create ridges in the lateral pharyngeal wall, referred to as the palatoglossal arches (anterior faucial pillars). These pillars separate the oral cavity and the oropharynx — the muscle functions as an antagonist to the levator veli palatini muscle.

The levator veli palatini is a muscle of the soft palate. Its primary function is to elevate the soft palate during swallowing, helping to prevent food from entering the nasopharynx. It is innervated by the pharyngeal branch of the vagus nerve.

Question 27

What muscles produce the following movements of tongue:
1. Protrusion (most important movement)
2. Retraction
3. Depression
4. Elevation (of posterior one-third)
5. Changes in shape

Answer 27

1. Protrusion (most important movement): Genioglossus muscles (of both side acting together)
2. Retraction: Styloglossus muscles (of both sides acting together)
3. Depression: Hyoglossus muscles (of both sides acting together)
4. Elevation (of posterior one-third): Palatoglossus muscles (of both sides acting together)
5. Changes in shape: Intrinsic muscles

Question 28

Which is the safety muscle of the tongue? Why is it called this?

Answer 28

Genioglossus.
Reason: The two genioglossi form the bulk of the tongue and are responsible for the protrusion of the tongue. If these muscles are paralyzed, the tongue will fall back into the oropharynx and obstruct the air passage causing choking and death. For the same reason during anesthesia, the tongue is pulled forwards to clear the air passage.

Question 29

The genioglossi are commonly used for clinical testing of the hypoglossal nerve. Explain.

Answer 29

The muscles of both sides acting together protrude the tongue whereas one muscle acting alone deviates the tongue to the opposite side. Therefore, when patient is asked to protrude his tongue, the tongue deviates to the paralyzed side (i.e., the side of lesion of the hypoglossal nerve).

NOTE: A question based on this explanation can be, State the anatomical basis of deviation of the tongue to the side of lesion of the hypoglossal nerve.

Question 30

State the arterial supply of the tongue.

Answer 30

1. Branches of lingual artery (chief artery of tongue); the deep lingual arteries to the anterior part [they are from which part of the lingual artery?] and dorsal lingual arteries [from which part of the lingual artery?] to the posterior part.
2. Tonsillar branch of the facial artery
3. Ascending pharyngeal artery
4. [Video: lingual artery]: starts from 3:23

Further notes:
The deep lingual artery anastomoses with its fellow of the opposite side near the tip of the tongue. It is the only significant anastomoses across the midline of the tongue.

Question 31

State the venous drainage of the tongue.

Answer 31

1. Deep lingual vein is the principal vein of the tongue and is visible on the inferior surface of the tongue near the median plane through thin mucous membrane in life. [Image]
2. Venae comitantes accompanying the lingual artery. They are joined by dorsal lingual veins.
3. Venae comitantes accompanying the hypoglossal nerve.

These veins unite at the posterior border of the hyoglossus to form the lingual vein, which drains into either common facial vein or internal jugular vein.

Question 32

Describe the lymphatic drainage of the tongue.

Answer 32

The lymphatics emerging from the tongue are grouped into the following four sets:
1. Apical vessels: They drain the tip and inferior surface of the tongue into submental lymph nodes after piercing the mylohyoid muscle. Their efferents go to the submandibular nodes mainly, some cross the hyoid bone to reach the jugulo-omohyoid nodes.
2. Marginal vessels: They drain the marginal portions of the anterior two-third of the tongue—unilaterally into submandibular lymph nodes and then to the lower deep cervical lymph nodes, including jugulo-omohyoid.
3. Central vessels: They drain the central portion of the anterior two-third of the tongue (i.e., area within 0.5 inch on either side of midline). They pass vertically downwards in the midline of the tongue between the genioglossus muscles and then drain bilaterally into the deep cervical lymph nodes.
4. Basal vessels: They drain the root of the tongue and posterior one-third of the tongue bilaterally into upper deep cervical lymph nodes, including jugulodigastric.

Question 33

Describe the nerve supply of the tongue.

Answer 33

Motor supply: All the muscles of tongue (intrinsic and extrinsic) are supplied by the hypoglossal nerve except palatoglossus which is supplied by superior laryngeal branch of CN X.
Sensory supply:
Anterior two-third of the tongue is supplied by:
(a) lingual nerve carrying general sensations, and
(b) chorda tympani nerve carrying special sensations of taste.
Posterior one-third of the tongue is supplied by:
(a) glossopharyngeal nerve, carrying both general and special sensations of taste, and
(b) posteriormost part (base of the tongue), supplied by the internal laryngeal branch of the superior laryngeal nerve carrying special sensations of taste.

Question 34

What is the anatomical basis of the pattern of innervation to the tongue?

Answer 34

Different embryological origins of development of the mucosa of tongue (ant. 2/3 from 1st and 2nd branchial arch and posterior 1/3 from largely 3rd and 4th branchial arches) and musculature of tongue from occipital myotomes.

Question 35

The roof of the oral cavity proper has two components, which are?

Answer 35

the bony hard palate (anterior four-fifth) and the musculofibrous soft palate (posterior one-fifth).

Question 36

Name the two bones that form the hard palate.

Answer 36

Palatine processes of the maxillae
Horizontal plates of the palatine bones
[Diagram]

Question 37

List the features on the inferior surface of the hard palate. If foramina are mentioned, state the contents passing through them.

Answer 37

(a) Incisive fossa, into which open the incisive canal/foramen.
Structures passing through the incisive canal:
☞ Terminal parts of the nasopalatine nerve [branch of the maxillary nerve]
☞ Greater palatine vessels [branch of descending palatine artery]
(b) Greater palatine foramen
Structures passing through:
☞ Greater palatine neurovasculature
(c) Lesser palatine foramina
☞ Lesser palatine neurovasculature
(d) Posterior nasal spine.
(e) Palatine crest
(f) Masticatory mucosa. It presents:
✓ transverse masticatory ridges on either side of mid-line, and
✓ palatine raphe, a narrow ridge of mucous membrane extending anteroposteriorly in the midline from a little papilla overlying the incisive fossa.
(g) Intermaxillary suture

[Diagram 1] [Diagram 2] [Image]

Note:
The hard palate is lined by stratified squamous keratinised epithelium.

Question 38

State the arterial supply and venous drainage of the hard palate.

Answer 38

Arterial supply: Greater palatine arteries from the 3rd part of maxillary artery. Each artery emerges from greater palatine foramen and passes forwards around the palate (lateral to the nerve) to enter the incisive canal and pass up into the nose.
Venous drainage: The veins of hard palate drain into the pterygoid venous plexus (mainly) and pharyngeal venous plexus.

Question 39

State the nerve supply and lymphatic drainage of the hard palate.

Answer 39

Nerve supply: By greater palatine and nasopalatine nerves derived from pterygopalatine ganglion. The greater palatine nerve supplies whole of the palate except anterior part of palate behind incisor teeth (the area of premaxilla), which is supplied by nasopalatine nerves.
Lymphatic drainage: The lymphatics from the palate drain mostly into the upper deep cervical lymph nodes and few into retropharyngeal lymph nodes.

Question 40

The soft palate is a mobile muscular flap, which hangs down from the posterior border of the hard palate into the _____________ cavity like a curtain or velum. It separates the nasopharynx from oropharynx.

Answer 40

pharyngeal

[Image]: uvula, patalopharyngeal arch, palatine tonsils, palatoglossal arch
[Diagram]

Question 41

The soft palate consists of five pairs of muscles. List them. Which of the five is intrinsic?

Answer 41

1. Tensor palati (tensor veli palatini)
2. Levator palati (levator veli palatini)
3. Palatoglossus
4. Palatopharyngeus
5. Musculus uvulae - intrinsic
6. [Diagram: Muscles of Soft Palate]

Question 42

Tensor palati (thin triangular muscle)
1. Origin
2. Insertion
3. Actions
4. Innervation

Answer 42

1. Origin: Scaphoid fossa of sphenoid bone; fibrous part of pharyngotympanic tube (lateral side of PTT); spine of sphenoid
2. Insertion: Muscle descends, converges to form a tendon, which hooks around the pterygoid hamulus and then expands to form the palatine aponeurosis for attachment to:
   * Posterior border of the hard palate
   * Inferior surface of the hard palate behind the palatine crest
3. Actions:
   ☞ Tenses the soft palate
   ☞ Opens the pharyngotympanic tube
4. Innervation: Mandibular nerve [V3] via the branch to medial pterygoid muscle
5. [7-minute video: the veli palatini muscles]
6. [Diagram]

Question 43

Levator veli palatini/Levator palati
1. Origin
2. Insertion
3. Actions
4. Innervation

Answer 43

1. Origin: (a) Medial aspect of the cartilaginous part of the pharyngotympanic tube
   (b) Adjoining part of the petrous temporal bone (inferior surface of its apex anterior to carotid canal)
2. Insertion: Superior surface of palatine aponeurosis
3. Actions:
   ☞ Only muscle to elevate the soft palate above the neutral position to close the pharyngeal isthmus.
   ☞ Opens the pharyngotympanic tube.
4. Innervation: Vagus nerve [X] via pharyngeal branch to pharyngeal plexus
5. [7-minute video: the veli palatini muscles]

Question 44

Palatopharyngeus [consists of two fasciculi, which are separated by the levator palati]
1. Origin
2. Insertion
3. Actions
4. Innervation

Answer 44

1. Origin: (a) Anterior fasciculus: from posterior border of the hard palate
   (b) Posterior fasciculus: from superior surface of palatine aponeurosis
2. Insertion: median fibrous raphe of pharyngeal wall [a connective tissue band along the posterior pharyngeal wall]
3. Actions:
   ☞ elevates pharynx (during swallowing)
   ☞ moves palatopharyngeal arch toward midline
   ☞ depresses soft palate
4. Innervation: Vagus nerve [X] via pharyngeal branch to pharyngeal plexus
5. [Diagram 1] [Diagram 2] [Diagram 3]

Further notes:
As palatopharyngeus descends along the pharyngeal wall from its origin, it forms a notable projection called the palatopharyngeal arch. This arch is located posteriorly to the palatoglossal arch and anteriorly to the palatine tonsil.

Question 45

Musculus uvulae
[a longitudinal muscle strip, one on either side of the median plane within the palatine aponeurosis]
1. Origin
2. Insertion
3. Actions
4. Innervation

Answer 45

1. Origin: Posterior nasal spine of hard palate
2. Insertion: Connective tissue of uvula
3. Actions:
   ☞ Elevates and retracts uvula
   ☞ Thickens central region of soft palate
4. Innervation: Vagus nerve [X] via pharyngeal branch to pharyngeal plexus

Question 46

State the functions/role of the soft palate.

Answer 46

1. Separates the oropharynx from nasopharynx during swallowing so that food does not enter the nose.
2. Isolates the oral cavity from oropharynx during chewing so that breathing is not affected.
3. Helps to modify the quality of voice, by varying the degree of closure of the pharyngeal isthmus.
4. Prevents the damage of nasal mucosa during sneezing, by appropriately dividing and directing the blast of air through both nasal and oral cavities.
5. Prevents the entry of sputum into nose during coughing by directing it into the oral cavity.

Question 47

What is the clinical picture of a patient with palatal paralysis?

Answer 47

The paralysis of the muscles of soft palate (due to lesion of vagus nerve) produces:
☞ nasal regurgitation of liquids,
☞ nasal twang in voice,
☞ flattening of the palatal arch on the side of the lesion,
and
☞ deviation of uvula, opposite to the side of the lesion.

[21-second video: Patient with paralysis of muscles of soft palate]: also in the video, notice the deviation of the patient’s uvula to the left

Question 48

What is the clinical significance of cleft palate?

Question 49

State the arterial supply, venous drainage and lymphatic drainage of the soft palate.

Answer 49

Arterial supply:
1. Lesser palatine branches of the maxillary artery.
2. Ascending palatine branch of the facial artery.
3. Palatine branches of the ascending pharyngeal artery.

Venous drainage: The venous blood from palate is drained into pharyngeal venous plexus and pterygoid venous plexus.

Lymphatic drainage: The lymphatics from soft palate drain into retropharyngeal and upper deep cervical lymph nodes.

Question 50

Describe the sensory innervation to the soft palate.

Answer 50

General sensations from palate are carried by:
☞ Lesser palatine nerves to the maxillary division of trigeminal nerve via pterygopalatine ganglion.
☞ Glossopharyngeal nerve.
Parasympathetic (to glands) and SA (taste on soft palate) fibers from a branch of the facial nerve [VII] join the nerves in the pterygopalatine fossa, as do the sympathetics (mainly to blood vessels) ultimately derived from the T1 spinal cord level.

Question 51

Describe the primary gustatory pathway of taste sensations from the:
a) anterior 2/3 of tongue except vallate papillae
b) posterior 1/3 of tongue including vallate papillae

Answer 51

a) anterior 2/3 of tongue ⇒ lingual nerve ⇒ chorda tympani nerve ⇒ geniculate ganglion ⇒ nervus intermedius ⇒ upper part of nucleus of tractus solitarius (aka gustatory nucleus)
b) posterior ⅓ of tongue ⇒ terminal branches ⇒ glossopharyngeal nerve ⇒ petrous ganglion (inferior ganglion of glossopharyngeal nerve) ⇒ central processes ⇒ gustatory nucleus

Question 52

Describe the primary gustatory pathway of taste sensations from the:
a) valleculae
b) soft palate

Answer 52

a) valleculae ⇒ internal laryngeal branch ⇒ vagus nerve ⇒ nodose ganglion ⇒ central processes ⇒ gustatory nucleus
b) soft palate ⇒ palatine nerves ⇒ greater petrosal nerve ⇒ geniculate ganglion ⇒ nervus intermedius ⇒ gustatory nucleus

Further notes:
Vallecula is a term that means depression in something. The epiglottic vallecula consists of a small mucosa-lined depression (vallecula) located at the base of the tongue just between the folds of the throat on either side of the median glossoepiglottic fold.
[Diagram 1: Epiglottic vallecula] [Diagram 2: Epiglottic vallecula] [Diagram 3: Epiglottic vallecula]

Question 53

Describe the pathway of the second order gustatory axons from the gustatory nucleus (upper part of solitary tract).

Answer 53

Second order gustatory axons start from the nucleus of the solitary tract and carry visceral impulses to the hypothalamus and the thalamus through the solitario- hypothalamic and solitariothalamic tracts, respectively. The fibres going to thalamus cross the midline and terminate in the ventral posteromedial nucleus (along with the trigeminal lemniscus). The nucleus of the solitary tract also sends fibres to the reticular formation, the general visceral efferent cranial nerve nuclei and to the autonomic nuclei (in the intermediolateral grey column) of the spinal cord.

Question 54

Describe the pathway of the third order gustatory axons.

Answer 54

Third order gustatory axons start from the ventral posteromedial nucleus of thalamus and radiate through the posterior limb of internal capsule to the inferior part of the postcentral gyrus of cerebral cortex and the insula. The ascending fibres ending in the hypothalamus, reach the limbic system, which allow autonomic reactions to taste.

Question 55

State the clinical relevance of the gustatory pathway.

Answer 55

Lesions of cranial nerves VII, IX, and X can affect taste sensation and result in ageusia (loss of taste), hypogeusia (decreased taste) or abnormal taste (dysgeusia).

Question 56

What is the gag/pharyngeal reflex? Why is it important?

Answer 56

Watch this 1:40 minute video first: [Video]
It is a protective reflex characterized by the elevation of the palate and contraction of the pharyngeal muscles with associated retching and gagging in response to stimulation of the mucous membrane of the oropharynx. It occurs when the palate, tonsil, posterior part of the tongue, or posterior pharyngeal wall are touched by unfamiliar objects such as swab, spatula, etc. The afferent limb of the reflex is provided by the glossopharyngeal nerve and efferent limb by the vagus nerve.