568
UNIT 3
Regulation and Integration of the Body
15
Gustatory Epithelial Cells
Te
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
to the surface of the epi-
thelium, where they are bathed by saliva. Te gustatory hairs are
the sensitive portions (
receptor membranes
) of the gustatory epi-
thelial cells. Coiling intimately around the gustatory epithelial
cells are sensory dendrites that represent the initial part of the
gustatory pathway to the brain. Each afferent fiber receives sig-
nals from several gustatory epithelial cells within the taste bud.
Tere are at least three kinds of gustatory epithelial cells. One
kind forms traditional synapses with the sensory dendrites and
releases the neurotransmitter serotonin. Te other two kinds
lack synaptic vesicles, but at least one releases A±P that acts as a
neurotransmitter.
Basal Epithelial Cells
Because of their location, taste bud cells
are subjected to friction and are routinely burned by hot foods.
Luckily, they are among the most dynamic cells in the body, and
they are replaced every seven to ten days.
Basal epithelial cells
act as stem cells, dividing and differentiating into new gustatory
epithelial cells.
Taste Buds and the Sense of Taste
Te word
taste
comes from the Latin
taxare
, meaning “to touch,
estimate, or judge.” When we taste things, we are in fact inti-
mately testing or judging our environment, and the sense of
taste is considered by many to be the most pleasurable of the
special senses.
Location and Structure of Taste Buds
Most of our 10,000 or so
taste buds
—the sensory organs for
taste—are located on the tongue. A few taste buds are scattered on
the soF palate, inner surface of the cheeks, pharynx, and epiglottis
of the larynx, but most are found in
papillae
(pah-pil
9
e), peglike
projections of the tongue mucosa that make the tongue surface
slightly abrasive. ±aste buds are located mainly on the tops of the
mushroom-shaped
fungiform papillae
(fun
9
jĭ-form) (which are
scattered over the entire tongue surface) and in the epithelium of
the side walls of the
foliate papillae
and of the large round
val-
late papillae
(val
9
āt). Te vallate papillae are the largest and least
numerous papillae, and 7 to 12 of them form an inverted V at the
back of the tongue
(Figure 15.22a, b)
.
Each flask-shaped taste bud consists of 50 to 100
epithelial
cells
of two major types:
gustatory epithelial cells
and
basal epi-
thelial cells
(²igure 15.22c).
(a) Taste buds are associated with
fungiform, foliate, and vallate papillae.
(b) Enlarged section of a
vallate papilla.
Fungiform
papillae
Taste bud
Vallate papilla
Epiglottis
Palatine tonsil
Foliate
papillae
Lingual tonsil
Taste fibers
of cranial
nerve
Connective
tissue
Gustatory
epithelial
cells
Taste
pore
Gustatory
hair
Stratified
squamous
epithelium
of tongue
(c) Enlarged view of a taste bud (210
m
).
Basal
epithelial
cells
Figure 15.22
Location and structure of taste buds on the tongue.
(For a related image,
see
A Brief Atlas of the Human Body
, Figure 62.)
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