description will here begin with the oesophagus or gullet.
The oesophagus (Gr. oiso, I will carry, and fagein, to
eat), a muscular tube lined with mucous membrane, stretches
from the lower limit of the pharynx, at the level of the
cricoid cartilage, to the cardiac orifice of the stomach.
It is about 10 in. long (25 cm.) and half to one inch in
diameter. At first it lies in the lower part of the neck,
then in the thorax, and lastly, for about an inch, in the
abdomen. As far as the level of the fourth or fifth thoracic
vertebra it lies behind the trachea, but when that tube ends,
it is in close contact with the pericardium, and, at the level
of the tenth thoracic vertebra, passes through the oesophageal
opening of the diaphragm (q.v.), accompanied by the two
vagi nerves, the left being in front of it and the right
behind. In the abdomen it lies just behind the left lobe of the
liver. Both in the upper and lower parts of its course it lies
a little to the left of the mid line. Its mucous membrane is
thrown into a number of longitudinal pleats to allow stretching.
The stomach (Gr. stomachos) is an irregularly pear-shaped
bag, situated in the upper and left part of the abdomen.
It is somewhat flattened from before backward and so has
an anterior and posterior surface and an upper and lower
border. When moderately distended the thick end of the
pear or fundus bulges upward and to the left, while
the narrow end is constricted to form the pylorus, by
means of which the stomach communicates with the small
intestine. The cardiac orifice, where the oesophagus
enters, is placed about a third of the way along the upper
border from the left end of the fundus, and, between it and
the pylorus, the upper border is concave and is known as
the lesser curvature. From the cardiac to the pyloric
orifice, round the lower border, is the greater curvature.
The stomach has in front of it the liver (see fig. 1), the
diaphragm and the anterior abdominal wall, while behind it
are the pancreas, left kidney, left adrenal, spleen, colon and
mesocolon. These structures form what is known as the stomach
chamber. When the stomach is empty it contracts into a tubular
organ which is frequently sharply bent, and the transverse
colon ascends to occupy the vacant part of the stomach chamber.
The last inch of the stomach before reaching the pylorus is
From A. Birmingham; Cunningham's Text-Book of Anatomy.
FIG. 1.--The Abdominal Viscera in situ, as seen when the abdomen
is laid open and the great omentum removed (drawn to scale from a
photograph of a male body aged 56, hardened by formalin injections).
The ribs on the right side are indicated by Roman numerals;
it will be observed that the eighth costal cartilage
articulated with the sternum on both sides. The subcostal,
intertubercular, and right and left Poupart lines are drawn
in black, and the mesial plane is indicated by a dotted
line. The intercostal muscles and part of the diaphragm
have been removed, to show the liver and stomach extending up
beneath the ribs. The stomach is moderately distended, and
the intestines are particularly regular in their arrangement.
usually tubular and is known as the pyloric canal. Before
reaching this there is a bulging known as the pyloric vestibule
(see D. J. Cunningham, Tr. R. Soc. of Edinib. vol. xlv.
pt. 1, No. 2). The pylorus is an oval opening, averaging
half an inch in its long axis but capable of considerable
distension; it is formed by a special development of the
circular muscle layer of the stomach, and during life is
probably tightly closed. The mucous membrane of the stomach
is thrown into pleats or rugae when the organ is not fully
distended, while between these it has a mammillated appearance.
Superficial to the mucous coat is a sub-mucous, consisting
of loose connective tissue, while superficial to this are
three coats of unstriped muscle, the inner oblique, the middle
circular and the outer longitudinal. The peritoneal coat is
described in the article on the coelom and serous membranes.
The small intestine is a tube, from 22 to 25 ft. long,
beginning at the pylorus and ending at the ileo-caecal
valve; it is divided into duodenum, jejunum and ileum.
The duodenum is from 9 to 11 in. long and forms a horseshoe
or C-shaped curve, encircling the head of the pancreas. It
differs from the rest of the gut in being retroperitoneal.
Its first part is horizontal and lies behind the fundus of
the gall-bladder, passing backward and to the right from the
pylorus. The second part runs vertically downward in
front of the hilum of the right kidney, and into this part
the pancreatic and bile ducts open. The third part runs
horizontally to the left in front of the aorta and vena
cava, while the fourth part ascends to the left side of
the second lumbar vertebra, after which it bends sharply
downward and forward to form the duodeno-jejunal flexure.
The jejunum forms the upper two-fifths of the rest of
the small intestine; it, like the ileum, is thrown into
numerous convolutions and is attached by the mesentery to the
posterior abdominal wall. (See COELOM AND SEROUS MEMBRANES.)
The ileum is the remaining three-fifths of the small
intestine, though there is no absolute point at which the
one ends and the other begins. Speaking broadly, the jejunum
occupies the upper and left part of the abdomen below the
subcostal plane (see ANATOMY: Superficial and Artistic),
the ileum the lower and right part. About 3 ft. from its
termination a small pouch, known as Meckel's diverticulum,
is very occasionally found. At its termination the ileum
opens into the large intestine at the ileo-caecal valve.
The caecum is a blind sac occupying the right iliac fossa and
extending down some two or three inches below the ileo- caecal
junction. From its posterior and left surface the vermiform
appendix protrudes, and usually is directed upward and to the
left, though it not infrequently hangs down into the true
pelvis. This worm-like tube is blind at its end and is
usually 3 or 4 in. long, though it has been seen as long as 10.
in. Its internal opening into the caecum is about 1 in. below
that of the ileum. On transverse section it is seen to be
composed of (1) an external muscular coat, (2) a submucous
coat, (3) a mass of lymphoid tissue, which appears after
birth, and (4) mucous membrane. In many cases its lumen is
wholly or partly obliterated, though this is probably due to
disease (see R. Berry and L. Lack, Journ. Anat. & Phys.
vol. H. p. 247). Guarding the opening of the ileum into
the caecum is the ileo-caecal valve, which consists of two
cusps projecting into the caecum; of these the upper forms a
horizontal shelf, while the lower slopes up to it obliquely.
Complete absence of the valve has been noticed, and in one
such case the writer found that no abdominal inconvenience had
been recorded during life. The caecum is usually completely
covered by peritoneum, three special pouches of which are
often found in its neighbourhood; of these the ileo-colic is
just above the point of junction of the ileum and caecum, the
ileocaecal just below that point, while the retro-caecal is
behind the caecum. At birth the caecum is a cone, the apex
of which is the appendix; it is bent upon itself to form a
U, and sometimes this arrangement persists throughout life
(see C. Toldt, ``Die Formbildung d. menschl. Blinddarmes,''
Sitz. der Wiener Akad. Bd. ciii. Abteil. 3, p. 41).
The ascending colon runs up from the caecum at the level of the
ileo-caecal valve to the hepatic flexure beneath and behind the
right lobe of the liver; it is about 8 in. long and posteriorly
is in contact with the abdominal wall and right kidney. It is
covered by peritoneum except on its posterior surface (see fig. 1).
The transverse colon is variable in position, depending largely
on the distension of the stomach, but usually corresponding
to the subcostal plane (see ANATOMY: Superficial and
Artistic). On the left side of the abdomen it ascends to the
splenic flexure, which may make an impression on the spleen (see
DUCTLESS GLANDS), and is bound to the diaphragm opposite the
eleventh rib by a fold of peritoneum called the phrenico-colic
ligament. The peritoneal relations of this part are
discussed in the article on the coelom and serous membranes.
The descending colon passes down in front of the left kidney
and left side of the posterior abdominal wall to the crest
of the ilium; it is about 6 in. long and is usually empty and
contracted while the rest of the colon is distended with gas;
its peritoneal relations are the same as those of the ascending
colon, but it is more likely to be completely surrounded.
The iliac colon stretches from the crest of the ilium
to the inner border of the psoas muscle, lying in the left
iliac fossa, just above and parallel to Poupart's ligament.
Like the descending, it is usually uncovered by peritoneum
on its posterior surface. It is about 6 in. in length.
The pelvic colon lies in the true pelvis and forms a
loop, the two limbs of which are superior and inferior
while the convexity reaches across to the right side of the
pelvis. In the foetus this loop occupies the right
iliac fossa, but, as the caecum descends and enlarges
and the pelvis widens, it is usually driven out of this
region. The distal end of the loop turns sharply downward
to reach the third piece of the sacrum where it becomes the
rectum. To this pelvic colon Sir F. Treves (Anatomy of
the Intestinal Canal, London, 1885) has given the name
of the omega loop. Formerly the iliac and pelvic colons
were spoken of as the sigmoid flexure, but Treves and T.
Jonnesco (Le Colon pelvien pendant la vie intra-uterine,
Paris, 1892) have pointed out the inapplicability of the
term, and to the latter author the modern description is due.
The rectum, according to modern ideas, begins in front of
the third piece of the sacrum; formerly the last part of the
O (or omega) loop was described as its first part. It ends
in a dilatation or rectal ampulla, which is in contact with
the back of the prostate in the male and of the vagina in the
female and is in front of the tip of the coccyx. The rectum
is not straight, as its name would imply, but has a concavity
forward corresponding to that of the sacrum and coccyx.
When viewed from in front three bends are usually seen, the
upper and lower of which are sharply concave to the left,
the middle one to the right. At the end of the pelvic colon
the mesocolon ceases, and the rectum is then only covered
by peritoneum at its sides and in front; lower down the
lateral covering is gradually reflected off and then only
the front is covered. About the junction of the middle and
lower thirds of the tube the anterior peritoneal covering
is also reflected off on to the bladder or vagina, forming
the recto-vesical pouch in the male and the pouch of
Douglas in the female. This reflexion is usually about 3
in. above the anal aperture, but may be a good deal lower.
The anal canal is the termination of the alimentary tract,
and runs downward and backward from the lower surface of
the rectal ampulla between the levatores ani muscles. It
is about an inch long and its lateral walls are in contact,
so that in section it appears as an antero-posterior slit
(see J. Symington, Journ. Anat. and Phys. vol. 23, 1888).
Structure of the Intestine.--The intestine has four coats:
serous, muscular, submucous and mucous. The serous or
peritoneal coat has already been described wherever it is
