Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
47
Fordøielsesorganerne.
Indgangen til Svælget, det saakaldte Atrium, har en
stærk Sphincter, der dannes af Spiserorets Ringmuskler,
idet disse forlænge sig op over den midterste Del af
Mundskiven, i hvis Centrum Atriet tindes. Dette er forsynet
med skarpt fremragende Længdefolder, der dog ganske ud- *
slettes, naar Mundaabningen er tilstrækkelig udvidet. Disse
Folder blive ved Sphincters Sammentrækning saa skarpe,
at enkelte Forfattere, f. Ex. Risso, har kaldt dem" Tænder.
Svælget er cylindrisk, omtrent 10""" langt, strækker
sig mindst 5 ""* bagenfor Vandkarringen, er meget muskulos,
har en mere eller mindre intens brun Farve, og et smukt
netformigt Udseende. Det er bundet til Kalkringen ved 5
dobbelte Længderækker af Muskelbaand. Disse bestaa af
en eller tiere Muskelbundter, som ere sammenbundne ved
et stærkt tibrillært Bindevæv. Rækkerne synes at følge
Kropsfeltcrne, saa at 3 falder paa Bugfladen og 2 paa
Rygsiden. I hver Række er der omtrent 10 Muskelbaand, der
ere bredest udad mod Kalkringen, hvor do inserere sig paa
Siden af Radialstykkerne.
Svælget bestaar af de samme Hudlag, som hele den
øvrige Tarmkanal, kun træde enkelte Lag i Svælget frem
med større Styrke, end paa de øvrige Steder. Svælgets
ydre Flade er beklædt med et flimrende Epithel, der
egentlig er Peritonealovertrækket; under dette tindes et
temmelig tyndt, gjennemsigtigt Bindevæv, som er sparsomt paa
Fibre, og hvori der ikke kunde iagttages Celler. Dette
ydre Bindevævslag støder umiddelbart til Muskelhudens
Ringinuskler, som her slutte sig tiet til hverandre, uden
dog at være anderledes sammenhængende, end at der
imellem hver Ringmuskel sees en fin Stribe af Bindevæv.
Længdemusklerne staa noget hengere fra hverandre, og idet
de overskjære Ringmusklerne, faar Muskelhuden et gittret
Udseende, ikke ulig Sipunkelhuden. Flere af
Længdemusk-lernes Fibre anastomosere med hverandre.
Indenfor Længdemusklerne tindes atter en
Bindevævs-hud, der bestaar af to Lag; det ydre Lag, der støder
umiddelbart til Længdemusklerne. er stærkt tibrilhert og
optages næsten ganske af en rig. netformig Karudbreduing;
det indre Lag er meget tykkere, temmelig gjennemsigtigt,
og i dette sees yderst fine Kalkkorn. hist og her enkelte
Fibre, og endelig en Mængde spredte, aflange klare Celler,
som indeslutte 8—12 gjennemsigtige Moleküler, de samme,
som tidligere ere omthlte i Hudens indre, hyaline
Bindevævslag. Paa dette indre Bindevævslag hviler Epithelet,
som er meget tykt. bestaar af tiere Lag lange Celler
(Cy-linderepithel). og udgjor den egentlige Slimhud, som her
danner tætstaaende Længdefolder, der rage ind i Svadget.
Hvor dette gaar over i Maven tindes udvendig en
ludsnøring.
Digestive Organs.
The entrance to the gullet, or atrium, as it is
called, has a powerful sphincter, the annular muscles of
the ojsophagus being prolonged up over the medial portion of
the oral disk, in the centre of which the atrium is located.
The latter is furnished with acuminate projecting
longitudinal folds, which, however, entirely disappear when the oral
aperture is sufficiently distended. On the contraction of
the sphincter, these folds assume so acuminate an
appearance, that some authors, Risso for instance, have given
them the name of teeth.
The oesophagus is cvlindric in form, about 10""" long,
extends 5"" at least behind the water-vascular ring, is
remarkably muscular, of a more or less deep-brown colour, and
has a fine reticulated appearance. It is webbed to the
calcareous ring by 5 double longitudinal series of muscular
bands, which consist of one or more fascicles of muscles,
webbed together by a strong tibrillous layer of connective
tissue. These series would seem to accompany the sections of the
body, so that 3 belong to the ventral and 2 to the dorsal
surface. Each series is furnished with about 10 muscular
bands, broadest externally towards the calcareous ring,
where they issue from the sides of the radial segments.
The oesophagus is composed of the same tegumentary
layers as the intestinal canal; but several of the
pharyngeal layers exhibit greater density than do those of the
latter organ. The outer surface of the oesophagus is invested
with a vibratile epithelium, in a strict sense the peritoneal,
tunic; beneath the latter extends a rather thin translucent
layer of connective tissue, sparingly furnished with fibres, and
in which’ no cells could be detected. This outer layer of
connective tissue is connate with tjje annular muscles of the
muscular tunic, between each pair of which, though their
arrangement here is comparatively close, may be discerned
a slender filament ol’ connective tissue. A somewhat wider
space intervenes between the longitudinul muscles, which, on
their intersecting the annular muscles, give to the skin a shiny,
glittering appearance, not unlike that characterising the
muscular tunic in Sipwmihis. Several of the fibres, in the
longitudinal muscles anastomose one with the other.
Underneath the longitudinal muscles extends another
stratum of connective tissue, composed of two layers ; the outer
layer, contiguous to the longitudinal muscles, is exceedingly
tibrillous, and almost entirely composed of a reticulate
vascular assemblage; in the inner layer, which is much thicker,
are seen exceedingly minute calcareous granules, here and
there, too, a few fibres, and. widely dispersed, numbers of
bright elliptic-shaped cells, containing from 8 to 12
translucent molecules, similar to those, already described, in the
inner hyaline layer of connective tissue. Over this inner layer
of connective tissue extends the epithelium, which is very
thick, consisting of several layers of elongate cells (the
cvlindric epithelium), and constitutes the mucous integument,
which here fonns closely arranged longitudinal folds,
projecting into the oesophagus. On the outer surface of the latter,
where it opens into the stomach, is seen a constriction.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
