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oesophagus and diaphragm, the cardiac orifice is the most fixed part of the stomach.
It is situated at the level of the body of the 10th or llth dorsal vertebra,
in front and to the left side of the aorta, and behind a notch in the posterior
surface of the left lobe of the liver. It lies, on an average, about 4 or 5 inches
posterior to the interval between the ensiform process and the inner end of the 7th
left costal cartilage. It appears from the researches of Braune and v. Gubaroff that
the cardiac orifice may have a valvular action independent of its muscular fibres.
Thus, after dividing the thorax horizontally some distance above the diaphragm,
and filling the stomach with fluid by injecting from the cut end of the oesophagus,
they found that the gastric contents were retained, although the oesophagus was not
ligatured. After piercing the diaphragm the oesophagus turns somewhat abruptly
to the left side to open into the stomach, and it is probable that when the stomach
is distended this bend is increased so as to obstruct the return of its contents into
the oesophagus.

Pylorus. From what has already been said regarding the movements of the
stomach, it is evident that the position of the pylorus in relation to the
anterior surface of the abdomen must vary considerably. As a rule, both in the
empty and in the distended state of the stomach it is overlapped in front by the
liver, which thus separates it from the abdominal wall. When the stomach is empty
the pylorus is in, or close to. the median plane, and an inch or so below the ensiform



THE STOMACFI.



73




process ; but, as already mentioned, it is found two or three inches to the right
of the median plane when the stomach is distended. Occasionally the pylorus
lies directly against the abdominal wall, just below the liver. The position
of the pyloric orifice can be recognized by a slight constriction on the outer;
surface of the organ, and also by a thickening of the wall, which can be
readily felt by taking it between the thumb and fore-finger. The closure of
this opsning is produced by the contraction of the circular muscular fibres,
which are well developed in this situation, and form a distinct projection
towards the orifice. This contraction at the pylorus is sometimes associated with
a similar condition of the muscular fibres of the stomach for an inch or more
from the pylorus, while the rest of the stomach is dilated. Viewed from its
duodenal side the closed pylorus presents some resemblance to the external os

Fig. 88. SECTION THROUGH PYLORIC PART OF

STOMACH AND COMMENCEMENT OP DUODENUM,
FROM A SPECIMEN HARDENED IN SITU. (J. S. ) \

a, a, a, longitudinal folds of the mucous mem-
brane in pyloric part of stomach ; b, section of
mucous membrane ; c, circular muscular fibres of
stomach, the longitudinal fibres are just visible to
the naked eye as a narrow line external to the
circular fibres ; D, duodenum ; p, pyloric orifice.



uteri, but the opening is stellate or
rounded. When the stomach and duo-
denum are distended and dried the open-
ing of the pylorus is usually circular, about half an inch in diameter, and bounded
by an annular projection. When distended and hardened with alcohol the annular
fibres at the orifice appear in section as a sharply marked band of considerable
thickness, producing a sharp prominence of the mucous membrane into the interior.

Borders. The borders of the stomach are termed the small and great curva-
tures. They give attachment to folds of peritoneum, between the layers of which
bloodvessels and lymphatics reach the organ. The small curvature is readily
recognized by its giving attachment to the small or gastro-hepatic omentum. It
passes from the cardiac orifice at first downwards and a little to the left, and then
turns somewhat abruptly to the right, to end at the upper border of the pylorus.
Near this opening it often has one or two depressions with intervening convex pro-
minences. The great curvature is four or five times as long as the small, and consists
of an upper, a left, and a lower portion. Traced from the oesophageal orifice it will be
found to pass to the left, forming an upwardly directed convexity, where it encircles
the upper part of the fundus. On the left side of the fundus it first passes nearly
straight downwards, and then turns to the right to end at the pylorus. The lower
part of the great curvature forms a convexity directed downwards ; it gives attach-
ment to the great or gastro-colic omentum, and usually has the transverse colon just
below it. Towards the pylorus its general curve may be interrupted by one or two
depressions.

Surfaces. The surfaces of the stomach are usually termed anterior and posterior,
but as already mentioned, the anterior surface looks more or less upwards and the
posterior downwards. Usually flattened when the stomach is empty, they become
convex on distension, so that in this condition the distinction between the borders
and surfaces of the organ is ill-defined. Behind the cardiac orifice there is a small
area of the stomach which is uncovered by peritoneum, and lies in direct contact with
the diaphragm (see fig. 87), and also often with the upper part of the left supra-
renal capsule. The reflection of the peritoneum at .the boundaries of this area from
the stomach to the diaphragm is called the gastro-phrenic ligament. With this
exception both surfaces of the stomach are entirely covered by peritoneum. On the



74 ORGANS OF DIGESTION.

posterior aspect near the left part of the great curvature the gastro- splenic omentum
is attached.

The anterior surface of the stomach is in contact with the under surface of the
left lobe of the liver and the diaphragm ; also, when distended, with the anterior

24 .




Fig. 89. VIEW OF THK STOMACH IN SITU AFTER REMOVAL OF THE LIVER AND THE INTESTINE (EXCEPT

THE DUODENUM AND COMMENCEMENT OF JEJUNUM). (Testut. )

A, diaphragm ; E, B', thoracico-abdominal parietes ; C, right kidney with c, its ureter ; D, right
suprarenal capsule ; E, left kidney with e, its ureter ; F, spleen ; G, G', aponeuroses of the transverse
abdominal muscles ; H, right quadratus lumborum muscle ; H', left ditto ; I, right psoas magnus and
parvus muscles ; I', left ditto ; K, oesophagus ; L, stomach ; M, duodenum ; N, jejunum ; the position
of the duodeno-jejunal junction behind the stomach is indicated by dotted lines. 1, termination of oeso-
phagus ; 2, great curvature of stomach ; 3, small curvature ; 4, fundus ; 5, antrum pylori ; 6, pyloric end ;
7, right vagus nerve ; 8, left ditto ; 9, thoracic aorta ; 9', abdominal aorta ; 10, inferior phrenic artery ;
11, cceliacaxis ; 12, hepatic artery ; 13, right gastro-epiploic ; 14, coronary artery ; 15, splenic artery ; 16,
16', superior mesenteric artery and vein ; 17, inferior mesenteric artery ; 18, spermatic arteries ; 19, gall
bladder ; 20, cystic duct ; 21, hepatic duct ; 22, inferior vena cava ; 23, portal vein ; 24, sympathetic cord.

abdominal wall and the quadrate lobe of the liver. Occasionally the transverse colon
is found in front of the stomach.

Posteriorly the stomach is in relation with the diaphragm, the spleen, the left
suprarenal capsule, the upper end of the left kidney, the pancreas, and the splenic
flexure of the colon. It is separated from the duodeno-jejunal junction and some
convolutions of the small intestine by the transverse mesocolon. The pyloric portion
of the stomach exhibits a tendency to sacculation owing to constrictions due to local
contractions of the muscular fibres. One or more of these constrictions are often
found on both the great and the small curvatures, but they seldom extend all round
the stomach, and can generally be obliterated by full distension. Occasionally, how-



THE STOMACH.



75



ever, a constriction occurs which is of a more permanent character, and partially
divides the stomach into two parts (hour-glass form).

Dimensions. These vary greatly in different subjects, and also according to the
state of distension of the organ. When moderately filled its length, measured from
the top of the fundus to the lowest part of the great curvature, is about 10 to 12
inches, and its diameter at the widest part from 4 to 5 inches. The distance



\




13 17 1G 19'

Fig. SO. VlEW OP THE LIVER, DUODKNUM, PANCREAS, SPLEEN, &C. THE GREATER PART OF THK
STOMACH HAS BEEN REMOVED TO SHOW ITS POSTERIOR RELATIONS J ITS POSITION IS INDICATED BY
A DOTTED OUTLINE. (Testut. )

A, inferior surface of liver ; B, right kidney ; C, C', right and left suprarenal capsules : D, left
kidney ; E, pancreas ; F, upper part of stomach ; Or, spleen ; H, duodenum with a, b, c, d, its four
portions ; I, jejunum ; K, duodeno-jejunal junction ; 1, lower end of oesophagus ; 2, pyloric orifice ; 3,
coeliac axis ; 4, coronai-y artery ; 5, hepatic artery ; 6, lobus Spigelii of liver ; 7, 7', splenic vessels ; 8.
left gastro-epiploic ; 9, right gastro-epiploic ; 10, superior mesenteric vessels ; 11, portal vein ; 12,
hepatic duct; 13, cystic duct ; 14, gall bladder ; 15, left crus of diaphragm ; 16, aorta ; 17, inferior
vena cava ; 18, inferior mesenteric vessels ; 19, 19', spermatic vessels.

between its two orifices varies from 3 to 6 inches. It weighs, when freed from other
parts, about 4|- ounces in the male and somewhat less in the female (Glendinning)
(about 200 grammes, Duroy). Its capacity is, on an average, about 5 pints (Brinton)
(2 to 3 litres).

Variations according to age. In the new-born child the stomach is small
and usually empty. Its general form and position are very similar to that of the
empty and contracted stomach in the adult, but in consequence of the large size of
the left lobe of the liver the whole of its anterior surface is covered by this organ.
When it becomes distended the movement of its pyloric portion towards the right
side is probably impeded by the large size of the liver.



76



ORGANS OF DIGESTION.




STRUCTURE OF THE STOMACH.

The stomach has four coats, named, in order from without inwards, the serous,
muscular, areolar or submucous, and mucous tunics (fig. 91).

The external or serous coat (s), derived from the peritoneum, is a thin,
smooth, transparent, and elastic membrane, which closely covers the entire viscus,
excepting along its two curvatures, and a small area near the cardiac end. Along
the line of these curvatures the attachment is looser, leaving an interval occupied
by the larger blood-vessels.

The second, or muscular coat, is composed of plain muscular tissue, forming

Fig. 91. SECTION THROUGH THE COATS OF THE STOMACH.
Diagrammatic. (Mall.)

m., mucous membrane ; e., epithelium ; d., orifice of gland
duct; m.m., muscularis mucoste ; sm., submucous coat; c.m.,
circular muscular layer ; l.m., longitudinal muscular layer ; s.,
serous coat.

three sets of fibres, disposed in layers, and named,
from their direction, the longitudinal, the circular,
and the oblique fibres.

The first or outermost layer consists of the longi-
tudinal fibres (fig. 91, l.m., fig. 92, A), which are in
direct continuity with those of the oesophagus. They
spread out in a radiating manner from the cardiac
orifice, and are found in greatest abundance along the
curvatures, especially the lesser one. On the anterior
and posterior surfaces they are very thinly scattered,
or scarcely to be found, but towards the pylorus are
well marked and form a thick uniform layer, which,
passing over the pylorus, becomes continuous with the
longitudinal fibres of the duodenum.

The second set consists of the circular fibres
(fig. 91, c.in,., fig. 92, B) which form a complete layer
over the whole extent of the stomach. They com-
mence by small and thinly scattered rings at the
extremity of the great cul-de-sac, describe larger and
larger circles as they surround the body of the stomach
at right angles to its curved axis, and towards the
pyloric end again form smaller rings, and at the same
time become much thicker and stronger than at any
other point. At the pylorus itself they are gathered
into a thick bundle (fig. 88, in section), which forms, within a circular fold of
mucous membrane, a well-marked projection the pyloric sphincter. Some of the
circular fibres appear to be continued from those of the oesophagus, spreading from
its right side.

The innermost muscular layer is incomplete, and consists of the oblique fibres
(fig. 92, c). These are continuous with the circular fibres of the gullet, on the
left of i he cardiac orifice, where they form a considerable stratum ; from that place
they descend obliquely upon the anterior and posterior surfaces of the stomach,
where they spread out from one another, and, taking the direction of the circular
fibres, gradually disappear on the greater curvature.

The submucous coat of the stomach is a distinct layer connecting the muscular
and mucous coats (fig. 91, s.m.). It consists of areolar tissue, in which occasional





THE STOMACH.



77



fat-cells may be found ; and it is the seat of division and passage of the blood-
vessels.

The internal coat or mucous membrane is a smooth, soft, ratner~thick and
pulpy membrane, which in the fresh state has generally a somewhat pink hue owing



Fig. 92. SKETCH OF THE AR-

RANGEMKNT OF THE FIBRES IN
THE MUSCULAR COAT OF THE

STOMACH. (Allen Thomson. )
J

A, external layer of longitu-
dinal fibres, as seen from the
outside ; B, middle layer of cir-
cular fibres as seen on removing
the longitudinal layer ; C, oblique
fibres exposed by removing some
of the fibres of the circular layer,
the cut edges of which are seen
below'the small curvature.

c, the cardiac end ; p, the
pyloric end ; in A, are shown the
stronger longitudinal fibres pass-
ing along the small and large cur-
vatures, and all round the pyloric
end, and radiating from the end
of the gullet over the front (and
back) of the stomach ; in B, the
nearly uniform layer of circular
fibres, in two sets crossing each
other very obliquely at o, and at
the cardiac end becoming con-
centric to the centre of the great
cul-de-sac ; in C, the obliquo
fibres, ob, oV , which form a con-
tinuation of the circular fibres of
the gullet (ce), and spread from
the left side of the cardia,
gradually merging into the deeper
circular fibres, with which finally
they entirely blend.



to the blood in its capillary
vessels. In infancy the
vascular redness is more
marked.

The mucous membrane
is thickest in the pyloric
region, and thinnest in the
great cul-de-sac. It always
becomes thinner in old age.

It is connected with the
muscular coat by means of
the intervening submucous
layer so loosely as to allow
of considerable movement
or displacement. In con-
sequence of this, and of the

want of elasticity of the mucous membrane, the internal surface of the stomach,
when that organ is in an empty or contracted state, is thrown into numerous
convoluted ridges, rugce, which are produced by the wrinkling of the mucous,
together with the areolar coat, and are entirely obliterated by distension of the




78 ORGAN'S OF DIGESTION.

stomach. These folds are most evident along the greater curvature, and have a
general longitudinal direction.

On examining the gastric mucous membrane closely with the aid of a simple
lens, it is seen to be marked throughout, but more plainly towards the pyloric
extremity, with small depressions which have a polygonal figure, and vary from
about 0'1~2 to 0'25 mm. across, being larger and more oblong near the pylorus.
They are the enlarged mouths or ducts of the tubular glands with which the mucous
membrane of the stomach is beset (fig. 91).

Towards the pyloric region of the stomach these depressions are larger and
deeper, and their margins are elevated into pointed processes, which resemble,
especially in vertical section, rudimentary villi, but the perfect forms of those
appendages exist only in the small intestine, and make their appearance in the
duodenum, immediately beyond the pylorus (fig. 91).

Epithelium of the surface. The thick stratified epithelium of the oesophagus
passes abruptly at the cardia into a simple layer of columnar epithelium, which
completely covers the inner surface of the stomach, and extends to a variable
distance into the mouths of the gastric glands. The transition of the stratified
into the columnar epithelium occurs quite suddenly, the lowermost columnar cells
of the stratified epithelium passing into the single columnar layer of the gastric
surface, and all the other layers of the stratified epithelium ceasing abruptly.

The epithelial cells of the surface of the stomach differ in some respects from
the columnar epithelium of the intestine. They are more elongated in form, and

Fig. 93. EPITHELIUM OF THK SURFACE OF THE STOMACH EXAMINED FRESH
(Heidenhain). HIGHLY MAGNIFIED.

in inactive conditions of the organ they exhibit two parts, the
attached end of the cell being granular, the free part that turned
towards the cavity of the organ occupied by a clear, muco-
albuminous substance (mucigen). Moreover, there is no striated border as in the
intestinal cells. The clear substance swells and is discharged from the cell during
digestion, leaving empty the part of the cell which contained it, and a similar change
is produced by water and various other reagents. Between the smaller ends of the
columnar cells, small, round, or oval cells occur, sometimes in small nests (Watney).

Gastric glands. As was first shown by Sprott Boyd, the surface of the stomach
within the depressions above mentioned is dotted with small round apertures, which
are the openings of minute glandular tubules, placed perpendicularly to the surface.
On making a vertical section of the membrane, and submitting it to microscopic
examination, it is seen to consist almost entirely of these small tubules, arranged
parallel with each other (fig. 91). Each mouth or duct, together with the tubules
which open into it, constitutes a gastric gland.

Some of the glands may be simple, consisting of a single tubule throughout, but
most are cleft into two or three tubules, or even, by the branching of these, eventually
into six or eight. The glands have externally a basement membrane, composed of
flattened cells joined edge to edge, and with processes which on the one side join the
re ti form tissue of the mucous membrane, and on the other side, more delicate, extend
in amongst and support the enclosed epithelium cells.

Two kinds of glands are distinguished, which differ from one another both in
the character of the enclosed cells, and, it is believed, in the nature of their secre-
tion. Those of the one kind (fig. 94), are simpler in structure than the others,
and being found most numerously in the pyloric region, they have been named
pyloric glands. These are distinguished by the large size and depth of the gland-
mouth as compared with the tubules which open into it, and by the character of




THE STOMACH.



79



the epithelium lining the tubules. The mouth of the gland is lined throughout
by an epithelium which is continuous with and similar to the columnar epithelium
which covers the general surface of the stomach. But in the tubulcs~of the gland
the lining cells are shorter and more cubical, and are uniformly finely granular
throughout ; moreover they are filled with secretion of a different nature from that of
the surface epithelium.

Amongst the cells of these glands there are occasionally found others which are
characterised by becoming darkly stained with osmic acid (Nussbaum). They have





Fig. 94. A PVLORIC GLAND, FROM A SECTION OF THE DOG'S STOMACH. (Ebstein. )

m, mouth ; n, neck ; tr, a deep portion of a tubule cut transversely.

Fig. 95. A CARDIAC GLAND OF SIMPLE FORM, FROM THE BAT's STOMACH. (Langley. )

Osmic acid preparation.

c, columnar epithelium of the surface ; n, neck of the gland with central and parietal cells ; /, base
or fundus, occupied only by principal or central cells, which exhibit granules accumulated towards the
lumen of the gland.

been supposed to represent the parietal cells of the cardiac glands (see below), but
this is probably not the case.

In the glands of the second kind (figs. 91, 95, 96) which may be termed, from
the portion of the stomach where they occur most numerously, the cardiac glands
(fundus glands of Heidenhain, oxyntic * glands of Langley) the mouth, or part
lined with epithelium like that of the surface, is comparatively short, and into it
open two, three, or more tubules which are lined throughout and almost filled with
short columnar or polyhedral cells ; these cells are in most respects similar to the



* From 6us, acid ; since they contain the cells which are believed to produce the acid of the gastric
secretion.



80



ORGANS OF DIGESTION.



secreting cells of the pylori c glands, but are much more coarsely granular. They
were termed by Heidenhain the principal cells of the glands ; they are also known
as the central cells. Between these cells and the basement membrane of the tubule
other cells of a different nature are interpolated in the cardiac glands. These are the

Fig. 96. A CARDIAC GLAND FROM THE DOG'S

STOMACH. (Klein and Noble Smith.)
Highly magnified.

d, duct or mouth of the gland ; l>, base
or fundus of one of its tubules. On the
right the base of a tubule more highly mag-
nified ; c, central cell ; p, parietal cell.

superadded, parietal, or oxyntic cells.
They were long thought to be the
only cells of the cardiac glands, and
were on that account known as




Fig. 97. A GASTRIC GLAND I TIIK LUMKN
SHOWN BY CHROMATE OF SILVER. (E.

Miiller.)

The cells are not represented, but the ex-
tension of the lumen into the networks
surrounding the parietal cells is well shown.

"peptic cells," a term which must
now be entirely discarded.

The parietal cells are rather more
closely arranged in the neck of the
gland than elsewhere. They usually cease abruptly at the upper part of the neck, but
occasional cells may be found under the columnar epithelium of the mouth or
even of the general surface. In the human stomach they are only absent from the
glands which are quite near the pylorus.



THE STOMACH,



In some animals (porpoise, pig) the parietal cells lie each in a special pit formed by base-
ment membrane, and communicating with the rest of the gland only by a narrow orifice. In
the glandular stomach of birds they line secondary tubules which lead out of the~matn tubule.
this alone being lined by principal cells. In the frog and other amphibia the cardiac glands

Fig. 98. CROSS-SECTION OF CARDIAC

GLANDS FROM THE HUMAN STOMACH,
SHOWING THE CONDITION OF THE

CELLS DURING FASTING. (Bohm and

.1 oo

; /, lumen of gland ;
t, connective tissue



v. Davidoff.)

c, central cell
parietal cell ;




between glands.

have only parietal or oxyntic cells,
the principal cells being altogether
absent, but glands containing cells
which are similar in appearance and
function to the principal cells of the
stomach are found in the oesophagus.

The parietal cells have a finely
granular appearance in the fresh
condition, but in the gland hardened
in alcohol are much darker and more
granular-looking. This appearance

is due, according to Klein, not to the presence of actual granules within the cells, but to the
existence of a close and uniform intracellular network (fig. 96). They are more readily
stained than the principal cells.

Fine intercellular passages extend from the lumen of the gastric glands between the
lining epithelium cells, and in the case of the cardiac glands these passages pass to the parietal
cells and invest them with a pericellular network (E. Mtiller) (fig. 97).




P-



Fig. 99. CROSS-SECTION OF CARDIAC GLANDS FROM THE HUMAN STOMACH, SHOWING THE CONDITION OF

THK CKLLS DURING DIGESTION. (Bohm and V. Davidoff.) 4QO

(References as in Fig. 98.)

The cells of the gastric glands undergo changes during the functional activity of the
organ which are strictly comparable to the changes that have been described in the cells of the
serous salivary glands. The principal cells of the cardiac glands are enlarged and almost fill
the lumen of the tubule in the intervals of digestion, and in this so-called " resting" or " loaded '
condition they are in some animals granular throughout, while in others there is a small outer
zone clear of granules. But they become smaller and distinctly differentiated into two zones
during activity, some of the granules becoming dissolved and discharged with the secretion,

VOL. III., PT. 4.



ORGANS OF DIGESTION.



and the rest tending towards the lumen of the gland so as to leave the outer half or third of



Online LibraryJones QuainQuain's Elements of anatomy (Volume 3:4) → online text (page 10 of 44)