The word taste comes from the Latin taxare, meaning “to
touch, estimate, or judge.”
• Most of the 10,000 or so taste buds are found on the tongue
• There are five basic taste sensations
– Sweet – sugars, saccharin, alcohol, and some amino acids
– Salt – metal ions
– Sour – hydrogen ions
– Bitter – alkaloids such as quinine and nicotine
– Umami – elicited by the amino acid glutamate
3. Taste buds
• Taste buds are found in papillae of the tongue mucosa
• Papillae come in three types: filiform, fungiform, and
circumvallate. Fungiform and circumvallate papillae
contain taste buds.
• Each flask-shaped taste bud consists of 50 to 100
epithelial cells of two major types:
1. Gustatory epithelial cells
2. Basal epithelial cells
4. The gustatory epithelial cells are the receptor cells for
taste the taste cells. Long microvilli called gustatory
hairs project from the tips of all gustatory epithelial cells
and extend through a taste pore.
Basal Epithelial Cells: This taste bud cells are subjected
to friction and are routinely burned by hot foods. They
are among the most dynamic cells in the body, and they
are replaced every seven to ten days
1. Vallate (circumvallate) papillae:- form an inverted V-shaped row
at the back of the tongue. Each of these papillae houses 100–30 taste
2. Fungiform papillae are mushroom-shaped elevations scattered
over the entire surface of the tongue that contain about five taste
3. Foliate papillae are located in small trenches on the lateral margins
of the tongue, but most of their taste buds degenerate in early
The entire surface of the tongue has filiform papillae. These pointed,
threadlike structures contain tactile receptors but no taste buds. They
increase friction between the tongue and food, making it easier for the
tongue to move food in the oral cavity.
8. Intrinsic Muscles
Superior longitudinal muscle:
Lies beneath mucous membrane
Shortens the tongue, make its dorsum concave
Inferior longitudinal muscle:
lying close to the inferior surface of the tongue
between genioglossus and hyoglossus
shortens the tongue, make its dorsum convex
extends from median septum to the margins
makes the tongue narrow and elongated
found at the borders of the anterior part of the tongue
makes the tongue broad and flattened
9. Extrinsic Muscles
origin: Upper genial tubercle of mandible
insertion: the fibres radiate widely to be inserted into the mucous membrane of
the tongue; the lowest fibres passing down to the hyoid body
origin: from the length of the greater horn of the hyoid bone and from lateral part
of its body
insertion: the fibres extend upward and its upper border interdigitating at right
angles with the fibres of styloglossus, and is attached to the side of the tongue
origin: from the front of the lower part of the styloid process and the upper part
of the stylohyoid ligament
origin: arises from the undersurface of the palatine aponeurosis
insertion: side of the tongue
10. Blood Supply and Venous Drainage
Tongue is supplied by the lingual artery
Drained through lingual vein
11. Physiology of Gustation
Chemicals that stimulate gustatory receptor cells are known as tastants.
Taste Transduction: Three different mechanisms underlie how we taste.
1. Salty taste is due to Na+ influx through Na+ channels, which directly
depolarizes gustatory epithelial cells.
2. Sour is mediated by H+, which acts intracellularly to open channels that allow
other cations to enter.
3. Bitter, sweet, and umami responses share a common mechanism, but each
occurs in a different cell. Each taste’s unique set of receptors is coupled to a
common G protein called gustducin. Activation leads to the release of Ca2+
from intracellular stores, which causes cation channels in the plasma
membrane to open, thereby depolarizing the cell and releasing the
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