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The ultrastructure of the human circumvallate papilla. I. Cilia of the papillary crypt

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The Ultrastructure of the Human
Circumvallate Papilla
I. CILIA OF THE PAPILLARY CRYPT
CARL F. T. MATTERN, WENDELL A. DANIEL AND
ROBERT I. HENKIN1
U.S. Department of Health, Education and Welfare, Public Health Service,
National Institutes of Health, National Institute of Allergy and
Infectious Diseases, Lnboratoiy of Viral Diseases and 1 National
Heart Institute, Experimental Therapeutics Branch,
Bethseda, Wlnryland 20014
ABSTRACT
Cilia-bearing cells have been observed near the bottom of the crypt of
the human circumvallate papilla, between the lower taste buds and the duct of van
Ebner's gland. It is likely that they serve one or more of the following functions: cleansing the papillary crypt, circulation of tastants, and bathing the pores of the taste bud
in the various fluid secretions of the oral cavity.
The kinetosomes of these cells were observed to possess typical transitional fibers and
rootlets with periodic structure. In addition, a single, lateral, satellite-like projection
from the midregion of the kinetosome was connected to microtubules which coursed
deeply with the mitochondria-rich cytoplasm as did fine fibrils and some rootlets.
Human circumvallate papillae are tion of cilia in this location will be preslightly raised, verrucous structures which sented.
are located on the posterior third of the
MATERIALS AND METHODS
tongue, mainly in or near the sulcus terminalis. A trench or crypt surrounds each
Several circumvallate papillae were surpapilla as a circular invagination of the gically excised in toto from a 42 year old,
epithelium. On the lateral aspect of the Caucasian female who subsequently unpapilla as many as 100 taste buds may be derwent surgery for a malignant process
found opening into the crypt (fig. 1 ) . Von involving the maxillary sinus. Prior to opEbner's glands are serous glands which lie eration, detection and recognition threshamong lingual muscle fibers beneath the olds for four .qualities of taste (salt, sweet,
epithelium of the floor of the crypt. Their sour and bitter) were measured in the oral
branching ducts converge to empty into cavity by techniques previously described
the bottom of the papillary trench (Bloom in detail (Henkin et al., '63; Henkin and
and Fawcett, '68).
Christiansen, '67). These thresholds were
Motile cilia are found extensively within within normal limits for each quality.
the respiratory tract. Other cilia, apparThe excised papillae were immediately
ently serving some function in sensory re- immersed in 2.5% glutaraldehyde i n phosception, are found in the olfactory epi- phate buffer (pH 7.4). After fixation for
thelium and in other sensory organs of at least 24 hours (4°C) the papillae were
man and other animals. However, they sectioned radially into six portions, posthave not been demonstrated in the oral fixed i n 1 % osmium tetroxide (phosphate
cavity i n higher animals. This communica- buffered to pH 7.4), and embedded in
tion will demonstrate the presence of cilia- epon-araldite. Sections were cut with a diabearing cells near the floor of the crypt of mond knife, stained successively with uracircumvallate papillae i n the vicinity of nyl acetate and lead citrate, and examined
both the taste buds and the ducts of von in RCA EMU 3E or 3H electron microEbner's glands. Some ultrastructural de- scopes.
tails of these ciliated cells will also be described. Hypotheses concerning the funcReceived Oct. 27, '69. Accepted Jan. 14. '70.
ANAT. REC., 167: 175-182
175
176
C . F. T. MATTERN, W. A. DANIEL A N D R. I. H E N K I N
RESULTS
of this row is virtuallv imaossible to determine by electron microscopy, and we have
been unable to identify these cells by light
microscopy. We have observed as many as
seven consecutive cilia-bearing cells in one
section. Cilia-bearing cells have been observed in three of six portions into which
a single papilla had been divided. They are
located approximately 0.25 to 0.50 m m
beneath the lowest taste buds.
The cytoplasm of the cilia-bearing cells
stains less densely and their mitochondria
are more numerous and more elongated
than the adjacent epithelial cells. About
280 cilia and kinetosomes are seen in the
large cluster (fig. 3 ) which represents the
cilia of a single cell. Numerous microvilli
are interspersed with the cilia.
I n figures 4 and 5 some details of the
kinetosome are seen. In addition to the
rootlet with its typical periodic structure
each kinetosome has a single lateral projec,
A typical circumvallate papilla is shown
schematically in figure 1. The lingual surface consists solely of epithelium which extends into the crypt. Over a substantial
portion of the lateral surface of the papilla
numerous taste buds open into the crypt
through pores. Internally the buds are continuous with unmyelinated nerves which
are present within the lamina propria along
with blood vessels, lymphatics, other unmyelinated nerve fibers and collagenous
stroma. The ultrastructure of the human
circumvallate taste bud will be the subject
of a subsequent communication.
A section nearly perpendicular to the
epithelial surface of the crypt is presented
in figure 2, and one tangent to the surface
in figure 3 . Cilia bearing cells are seen surrounded by epithelial cells and they appear
to be arranged in a double row. The extent
A
Fig. 1 Schematic drawing of a circumvallate papilla. L, lingual surface; E, epithelium; B, taste
buds; P, taste pores; C, cilia; D, duct of von Ebner’s gland, G ; L. P. lamina propria containing nerves,
N. Blood vessels, lymphatics, unmyelinated nerve fibers not related to the taste buds and the collagenous stroma are not shown for purposes of ciarity.
CILIA OF THE CIRCUMVALLATE PAPILLA
177
Fig. 2 A section nearly perpendicular to the epithelial surface showing two cilia-bearing cells. C,
cilia; K, kinetosomes; MV, microvilli; M, mitochondria. x 6,500.
tion which i s reminiscent of satellite structures frequently seen around centrioles
(Fawcett, '66). In addition, near the cell
membrane the kinetcisomes demonstrate
transitional fibers which appear as nine
radiating spokes and which presumably attach to the inner surface of the cell.
A number of microtubules are also seen
in figure 4 apparently coursing from the
kinetosome to a n unknown region deeper
within the cytoplasm. As may be seen in
figure 6 one or possibly more microtubules
appear to arise from or attach to the lateral
satellite.
In several sections we have observed
large rootlet structures deep in the cytoplasm of cilia-bearing cells. Such a rootlet
is seen near the nucleus in figure 7.
178
C. F. T. M A T T E R N , W. A. D A N I E L AND R. I. HENKIN
Fig. 3 A section nearly tangent to the epithelial surface of cilia-bearing cells. Legends a s in figure 2. >: 7,000.
In other cilia-bearing cells both microtubules and fine fibrils are interspersed with
mitochondria and in some instances the
fine fibrils are closely applied to mitochondria.
DISCUSSION
To our knowledge this is the first demonstration of the presence of locomotor cilia
on the tongue of vertebrates. In the human
circumvallate papilla these cilia-bearing
Fig. 4 Higher magnification of a section similar to figure 2. C, cilia; MV, microvilli; K, kinetosomes; R, rootlets; S, satellite-like, lateral projection; MT, microtubules; M. mitochondria. x 26,200.
Fig. 5 Higher magnification of a portion of figure 3. In addition to numerous cilia, microvilli,
and kinetosomes, in cross section, satellite-like lateral projections ( S ) and superficial transitional
fibers ( T ) are apparent. x 15,000.
180
C . F. T. MATTERN, W . A. DANIEL AND R. I. HENKIN
Fig. 6 Three views of kinetosomes ( K ) and lateral satellites ( S ) with attached microtubules (arrows), left x 26,100, center and right X 46,500.
Fig. 7 Kinetosomal rootlets (R) deep in the cytoplasm are seen near the nucleus ( N ) of a ciliabearing cell. x 28,000.
CILIA OF THE CIRCUMVALLATE PAPILLA
cells probably serve one or more of three
functions : ( 1) removal of detritus and general cleansing of the crypt of the papilla;
(2) assistance in the process of taste by
circulation of tastants; and (3) circulation
of the serous secretion of von Ebner's
gland and other oral fluids which bathe
the pores of these taste buds. Taste buds
must be continually bathed in order for
normal taste acuity to be maintained. This
suggests an important relationship between
cilia-bearing cells and oral secretions. This
is supported by observations made in patients with Sjoegren's syndrome (rheumatoid arthritis with xerostomia and xerophthalmia) which indicate both a decreased
taste acuity and absence of oral fluids
(Henkin unpublished observations).
As yet it is not possible to deduce the
specifk function of the complex structures
associated with the kinetosomes. These include the periodic rootlets, the lateral,
satellite-like projections with attached microtubules passing into the mitochondriarich cytoplasm, and the fine filaments seen
in proximity to the mitochondria. Similar
periodic rootlets are commonly associated
with kinetosomes throughout the animal
kingdom and microtubules are often associated with centrioles and kinetosomes,
181
either directly or through satellites. The
presence of mitochondria in proximity to
these complexes suggests a role in supplying ATP as the energy source of cilia and
flagella (Sleigh, '62).
In a wide variety of systems these various structures have been implicated in a
number of roles: support, coordination of
cilia, ciliary bending, contraction or flexion
and other specialized functions. However
their speciflc structural-functional relationships are not completely understood
(Sleigh, '62).
LITERATURE CITED
Bloom, W., and D. W. Fawcett 1968 A textbook
of histology. W. B. Saunders Co., Ninth edition,
Philadelphia.
Fawcett, D. W. 1966 An atlas of fine structure.
W. B. Saunders Co., Philadelphia.
Henkin, R. I., and R. L. Christiansen 1967
Taste localization on the tongue, palate and
pharynx of normal man. J. Appl. Physiol.. 22:
316.
Henkin, R. I., J. R. Gill, Jr., and F. C. Bartter
1963 Studies in taste thresholds in normal
man and in patients with adrenal cortical insufficiency: The role of adrenal cortical steroids
and of serum sodium concentration. J. Clin.
Invest., 42: 727.
Sleigh, M. A. 1962 The biology of cilia and
flagella. Permagon Press Ltd., Oxford.
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