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The utricular fold in the adult human ear.

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THE TJTRICULAR FOLD I N THE ADULT HUMAN EAR1
BARRY JOSEPH ANSOX AND JOHN GORDON WILSOhDepurtments of Anatomy and Oto-lnryngology, Northwestern Unicersity
Medical School
ONE PLATE
(mi70
FIGURES)
The utricular fold, which was seen, apparently for the first
time, by Bast2 in a 183-mm. human fetus, has been described
by the present writers in the preceding number of this journal
as observed in the two-year-old child. Now, its discovery in
the adult human ear seems to establish the structure as a
permanent feature of the membranous labyrinth in man.
Tlic fold has been found in series of sections from eleren
adult ears in Doctor Wilson’s collection. The specimens
were secured a number of years ago, at which time they were
fixed in 10 per cent formalin t x o o r three hours after the
subject’s death; they were stored in formalin until recently,
when they were decalcified in 3 per cent nitric acid in 10 per
cent formalin, cut as celloidin sections 30 p thick, and stained
with haematoxylin and eosin. The fold in one series only has
been selected f o r description here, although, in general, its
features as seen in sections are similar throughout the lot of
specimens.
The fold represents, as it does likewise in the child, the
posteromedial wall of the utricle as this is applied to the
adjacent wall of the endolymphatic duct (fig. 1). These two
epithelial layers, separated by a stratum of connective tissue,
are carried backward as a shank of diminishing thickness
into a foot-like free extremity; in curving lateralward the foot
Contribution no. 144 from the Anatomical Laboratory of N o r t h w s t e n i
University Medical School.
T. H. Bast, Anat. Rec., vol. 40, 1928, pp. 61-64.
“31
is luought near the posterior wall of the utricle and in that
location constitutes the anterior boundary of the utriculoendolymphatic duct. The fold is twice as long (1.52 mm.)
and one-half again as thick (0.18 mm.) a s the same structuro
in the child; its width is slightly increased.
Tlic plane of sectioning is such that through three sections
tlie 1)rojection appears as a true fold, beneath whose distal
c.iitl there is a direct communication between utricle and endolymphatic duct; through eight additional sections, only a port ioii of this communication-the
utriculo-endolymphatic duct
-exists, so that the free end of tlie shank with its foot, or the
foot alone, then occurs a s a short flap of tlie utricular wall.
Fa r t h e r i n either direction in the series, it becomes a n undertaut ridge, then merely a terrace of gradually decreasing
height, which finally merges into the utricular wall.
The fold is covered with cuboidal epithelial cells (fig. a ) ,
somewlist flattened on a p a r t of that aspect wliich faces the
cridolympliati(~duct ; the nuclei a r e correspondingly round or
oval. The cells possess a well-defined cuticular border on
their free surfatv, -cvhicli is continuous with a similar interc~ellalarsubstance and a thinner basement membrane.
‘The core of the fold is made up of areolar tissue, rather
wlliilar and loosely arranged. The cells generally consist
of a vc~rythin rim of cytoplasm wliich encloses a n oval nucleus
mid is carried out into fine processes; a few, however, possess
chlongate shrunken nuclei like those of adult connective tissue ;
fewer still seem to b~ typical fibroblasts. I n the shaft the
wlls a r e placed with their long axes u p and down; in the
fool they extend across the fold, and so are cut transversely.
l a the proximal fourth of tlie fold the areolar tissue passes
into a very coilcentrate fibrous feltwork, which suggests the
d l a g e n o u s groundwork of developing bone or, because of the
abseiice of osteoblasls, it spear-shaped projection of periosteal
tissue. This is continuous with a projection of the O S S C O ~ S
.i\.all wliich, as a spicule, extends to, but not into, the fold
proper.
1)lood ressel courses just beneath the epithelium
on 1 ho ut ricwlnr aspcct of thc core.
PLATE
w r of L:
Iiumnn :rclult.
sac., sacculns
A c t . , scltla tgmp:iiii
~c.v., scala vestibuli
utr., utriculus
wst., x estibulutn
p11c:t 1ltrlcul:Irls
Z’l.llt,.,
ABBRh,VIhlTO.h, b
b.st., basis stapedis
c’.t., CAT urn tgnipaiii
rise., duetus endolympliatieus
m a t . , meatus acustieus intrrnus
’1 J., ner vus cochlcae
3%5.
6.m., ba5is modioli
x
1 Section shows tlie u t r i c t h r fold %\it11its foot-likc c,.\treniity applied to the
utrieuhr wall. and its relation to utriclc :mil endolyniplratie duct. x 12.
2 Portion of the same scotion a t increnscil magnification, showing tlie free
end of the utricular fold w i t h its epithelial covering and enclosed areolar tissue.
1’~iototiiicrogr:tplis. llorimiital scvtion of the intcrnal
EAPLANATION OF b”IGCIRL6
01
01
tu
I
UTI%lOULA&FOLD IN TEE ADULT IIUMAN EAR
HAlLBY JOSEI’H LlBoh’ A1D JOIIN QORDON WlLSON
2
PLATE 1
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