Taste is sensed by taste buds located in the mouth. There are about 10,000 taste buds located in the papillae and walls of the tongue. Taste buds contain taste receptor cells that detect the five basic taste modalities: sweet, sour, salty, bitter, and umami. Taste information travels along cranial nerves to the brainstem and thalamus before reaching the primary gustatory cortex. All areas of the tongue can sense all tastes. Bitter is the most sensitive taste while sweet is the least. A 30% change in concentration is needed to detect an intensity difference. Abnormalities include ageusia (lack of taste), hypogeusia (diminished taste), and dys

1. Taste
Dr. Berjin
Jr Resident
Department of Physiology

2. • The sense organ for taste is the taste buds
• About 10,000 taste buds
• Receptors for taste are called taste receptors
or gustatory receptors or taste cells

3. Structure of taste bud
• Ovoid in shape
• Made up of 4 types of cells:
• - Basal cells
• - Dark cells
• - Light cells
• - Intermediate cells
• The taste cells have
microvilli that project into the
taste pore
• Afferent fibres arise from the taste cells, each taste bud
is innervated by about 50 nerve fibres

4. Location of taste buds
• Taste buds are located in the mucosa of the
• Epiglottis
• Palate
• Pharynx
• Walls of papillae of tongue

5. Types of papillae in the tongue
1.The Fungiform papilla
2.The Circumvallate papilla
3.Foliate papilla

6. Types of papillae in the tongue
• Fungiform papillae – rounded structures near
the tip of the tongue (about 5 taste buds
each)
• Circumvallate papillae – arranged in a V in the
back of the tongue (about 100 taste buds
each)
• Foliate papillae : posterior edge of the tongue
(about 100 taste buds each)

8. Taste Pathway

9. Taste pathway
• The sensory nerve fibers from the taste buds on the anterior two-
thirds of the tongue travel in the chorda tympani branch of the facial
nerve
• Taste sensations from the posterior third of the tongue reach the
brain stem via the glossopharyngeal nerve
• The fibers from other areas other than the tongue (eg, pharynx)
reach the brain stem via the vagus nerve
• The taste fibres in the three nerves unite in the gustatory portion of
the nucleus of the solitary tract (NTS) in the medulla oblongata

10. Taste pathway
• From the nucleus of solitary tract, axons of second-order
neurons ascend in the ipsilateral medial lemniscus and
pass directly to the ventral posteromedial nucleus of the
thalamus
• From the thalamus, the axons of the third-order neurons
pass to neurons in the anterior insula and the frontal
operculum (primary gustatory area in the parietal lobe) in
the ipsilateral cerebral cortex

11. Basic taste Modalities
• Sweet
• Sour
• Salty
• Bitter
• Umami - taste sensation triggered by monosodium
glutamate, pleasant & sweetish

12. Any special areas on the tongue for
each taste sensation?
• All taste sensations are sensed from all parts
of the tongue

13. Taste thresholds and intensity
discrimination
• Most sensitive to taste receptors – Bitter
• Least sensitive to taste receptors – sweet
• A 30% change in the concentration of the
substance being tasted is necessary before an
intensity difference can be detected

14. Abnormalities of taste
• Ageusia : absence of sense of taste
• Hypogeusia : diminished taste sensitivity
– Causes : Damage to the lingual or glossopharyngeal
nerves, Bell’s palsy
• Dysgeusia or parageusia : Unpleasant perception
of taste : can be caused by the above factors

15. • Ganong ‘s review of Medical Physiology