Taste buds and there function

 TASTE BUDS

Sense organs for taste or gustatory sensation are the taste buds. Taste buds are ovoid bodies with a diameter of 50 μ to 70 μ. In adults, about 10,000 taste buds are present and the number is more in children. In old age, many taste buds degenerate and the taste sensitivity decreases.

SITUATION OF TASTE BUDS

Most of the taste buds are present on the papillae of tongue. Taste buds are also situated in the mucosa

of epiglottis, palate, pharynx and the proximal part of esophagus.

Types of papillae located on tongue:

1. Filiform papillae

2. Fungiform papillae

3. Circumvallate papillae.

1. Filiform Papillae

Filiform papillae are small and conical-shaped papillae, situated over the dorsum of tongue. These

papillae contain less number of taste buds (only a few).

2. Fungiform Papillae

Fungiform papillae are round in shape and are situated over the anterior surface of tongue near the tip.

Numerous fungiform papillae are present. Each papilla contains moderate number of taste buds (up to 10).

3. Circumvallate Papillae

Circumvallate papillae are large structures present on the posterior part of tongue and are many in number. These papillae are arranged in the shape of ‘V’. Each papilla contains many taste buds (up to 100).

STRUCTURE OF TASTE BUD

Taste bud is a bundle of taste receptor cells, with supporting cells embedded in the epithelial covering

of the papillae. Each taste bud contains about 40 cells, which are the modified epithelial cells.

Cells of taste bud are divided into four groups:

Type of Cells in Taste Bud

1. Type I cells or sustentacular cells

2. Type II cells

3. Type III cells

4. Type IV cells or basal cells.

Type I cells and type IV cells are supporting cells. Type III cells are the taste receptor cells. Function

of type II cell is unknown. Type I, II and III cells have microvilli, which project into an opening in epithelium

covering the tongue. This opening is called taste pore. Neck of each cell is attached to the neck of other. All the cells of taste bud are surrounded by epithelial cells. There are tight junctions between epithelial cells and the neck portion of the type I, II and III cells, so that only the tip of these cells are exposed to fluid in oral cavity.

APPLIED PHYSIOLOGY – ABNORMALITIES OF TASTE SENSATION

AGEUSIA

Loss of taste sensation is called ageusia. Taste buds in anterior two thirds of the tongue are innervated by the chorda tympani branch of facial nerve. Chorda tympani nerve receives taste fibers from tongue via

lingual branch of mandibular division of trigeminal nerve. So, the lesion in facial nerve, chorda tympani or

mandibular division of trigeminal nerve causes loss of taste sensation in the anterior two third of the tongue. Lesion in glossopharyngeal nerve leads to loss of taste in the posterior one third of the tongue.

Temporary loss of taste sensation occurs due to the drugs like captopril and penicillamine, which

contain sulfhydryl group of substances.

HYPOGEUSIA

Hypoguesia is the decrease in taste sensation. It is due to increase in threshold for different taste sensations. However, the taste sensation is not completely lost.

TASTE BLINDNESS

Taste blindness is a rare genetic disorder in which the ability to recognize substances by taste is lost.

DYSGEUSIA

Disturbance in the taste sensation is called dysgeusia. It is found in temporal lobe syndrome, particularly

when the anterior region of temporal lobe is affected. In this condition, the paroxysmal hallucinations of

taste and smell occur, which are usually unpleasant.

 

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