Olfactory and Gustatory System I: Anatomy, Physiology and control

Question 1

Name parts of the Olfactory and Gustatory System

Answer 1

Tongue
Pharynx 
epiglottis
Larynx 
Trachea
oesophagus
Cerebrum 
Nasal Cavity
Cribriform plate
Frontal sinus
Nasopharynx
Cerebellum 
Brainstem
Oropharynx
Hard palate
soft palate
External nares
Buccal cavity
Lyssa 
Frenulum
Vomeronasal Organ
Tongue
Pharynx epiglottis
oesophagus

Question 2

Design of the tongue:

Answer 2

• Intrinsic musculature
• Extrinsic musculature
• Contains taste buds, salivary glands

Question 3

Intrinsic musculature of the tongue

Answer 3

The intrinsic muscles only attach to other structures in the tongue. There are four paired intrinsic muscles of the tongue and they are named by the direction in which they travel: the superior longitudinal, inferior longitudinal, transverse and vertical muscles of the tongue. These muscles affect the shape and size of the tongue – for example, in tongue rolling – and have a role in facilitating speech, eating and swallowing.

Motor innervation for the intrinsic muscles of the tongue is via the hypoglossal nerve (CNXII).

Question 4

Extrinsic musculature of the tongue

Answer 4

Genioglossus

Attachments: Arises from the mandibular symphsis. Inserts into the body of the hyoid bone and the entire length of the tongue.
Function: Inferior fibres protrude the tongue, middle fibres depress the tongue, and superior fibres draw the tip back and down
Innervation: Motor innervation via the hypoglossal nerve (CNXII).

Hyoglossus

Attachments: Arises from the hyoid bone and inserts into the side of the tongue
Function: Depresses and retracts the tongue
Innervation: Motor innervation via the hypoglossal nerve (CNXII).
Styloglossus

Attachments: Originates at the styloid process of the temporal bone and inserts into the side of the tongue
Function: Retracts and elevates the tongue
Innervation: Motor innervation via the hypoglossal nerve (CNXII).

Palatoglossus

Attachments: Arises from the palatine aponeurosis and inserts broadly across the tongue
Function: Elevates the posterior aspect of the tongue
Innervation: Motor innervation via the vagus nerve (CNX).
All of the intrinsic and extrinsic muscles are innervated by the hypoglossal nerve (CN XII), except palatoglossus, which has vagal innervation (CN X).

Question 5

Innervation of tongue

Answer 5

• Rostral two thirds of the tongue general sensory innervation is relayed by the lingual branch of the mandibular nerve, V3, and the chorda tympani relays the special sensation of taste.
• Caudal third of the tongue sensory innervation by the glossopharyngeal nerve and to a small extent by the vagus nerve.
• Intrinsic and extrinsic muscles of the tongue are innervated by the hypoglossal nerve.

Question 6

Filiform papillae

Answer 6

Filiform papillae are the most numerous of the lingual papillae. They are fine, small, cone-shaped papillae covering most of the dorsum of the tongue. They are responsible for giving the tongue its texture and are responsible for the sensation of touch.

They offer additional protection to the mucosal surface of the tongue. In addition to the filiform papilla the mucosa of the tongue may be keratinised to varying degrees dependant on the abrasiveness of the diet

Question 7

Foliate papillae

Answer 7

The foliate papillae are involved in the sensations of taste and have taste buds embedded in their surfaces. The foliate papillae are clustered into two groups positioned on each side of the tongue

Question 8

Circumvallate papillae

Answer 8

Circumvallate papillae are located at the base of your tongue. They’re large and round, and they house several thousand taste buds.

Question 9

Taste buds

Answer 9

The taste buds are embedded in the epithelium of the tongue and make contact with the outside environment through a taste pore. Slender processes (microvilli) extend from the outer ends of the receptor cells through the taste pore, where the processes are covered by the mucus that lines the oral cavity. At their inner ends the taste receptor cells synapse, or connect, with afferent sensory neurons, nerve cells that conduct information to the brain. Each receptor cell synapses with several afferent sensory neurons, and each afferent neuron branches to several taste papillae, where each branch makes contact with many receptor cells. The afferent sensory neurons occur in three different nerves running to the brain—the facial nerve, the glossopharyngeal nerve, and the vagus nerve. Taste receptor cells of vertebrates are continually renewed throughout the life of the organism.

Question 10

Vomeronasal Organ

Answer 10

• Detects oestrus
• Links Taste and Smell
• Can detect hormone and pheromone
levels by licking
• Flehmen response

Question 11

Clinical test of olfactory function

Answer 11

• Smell can be tested by seeing a response to an invisible smell, (often blindfolded).
• Gustatory