Dr. Dharmakanta Kumbhakar
Taste is the perception of sweet, sour, bitter or salty by the tongue. In the tongue, the sweet sensitivity is greatest at the tip, sour at the sides, bitter at the back, while salt sensitivity is more homogeneous but greatest in the tip. The mid-dorsum of the tongue is insensitive to all tastes. The taste receptor cells are chemoreceptors which are stimulated by substances (Tastants) dissolved in the oral fluids are located in the taste buds.
In humans, the total number of taste buds is about 10,000 which decrease in the old age. The taste buds are located in the papillae along the lateral margin and dorsum of the tongue, at the junction of the dorsum and the base of the tongue, and in the palate, pharynx and epiglottis. Individual taste buds can respond exclusively to salt, sweet, bitter or sour substances or to some combination of two, three or four of the basic taste stimuli.
Disorders of the sense of taste may be categorised as:
(1) Total Ageusia: The total absence of gustatory function or inability to detect the qualities of sweet, salt, bitter or sour.
(2) Partial Ageusia: The ability to detect some of but not all qualitative gustatory sensations; specific ageusia- inability to detect the taste quality of certain substances.
(3) Total Hypogeusia: Decreased sensitivity to all tastants; partial hypogeusia- decreased sensitivity to some tastants.
(4) Dysgeusia or Phantogeusia: Distortion in the perception of a tastant, i.e. the perception of the wrong quality when a tastant is presented or the perception of a taste when there has been no tastant ingested. Electrogustometry is an electric taste testing to identify taste deficits in specific quadrants of the tongue.
Disorders of the sense of taste are caused by:
(1) Conditions that interfere with the access of the tastant to the receptor cells in the taste buds (transport gustatory losses- due to drugs, heavy metal intoxication, radiation therapy, sjogren’s syndrome, xerostomia).
(2) Injured receptor cells (sensory gustatory losses due to aging, candidiasis, antithyroid and antiepileptic drugs, endocrine disorders, oral neoplasms, pemphigus, radiation therapy, herpes virus infections).
(3) Damage gustatory afferent nerves and central gustatory pathways (neural gustatory losses due to hypothyroidism, diabetes mellitus, oral neoplasms, oral surgery, radiation therapy, renal diseases, stroke and other CNS disorders, trauma, upper respiratory infections).
(Dr. Dharmakanta Kumbhakar can be reached at 9864517168 or by e-mail at email@example.com.)