« PrécédentContinuer »
The pylorus rests on the neck of the pancreas below and posteriorly, and is overlapped by the liver above and anteriorly. When the stomach is empty the pylorus is usually placed near (i.e. within inch, 12 mm. of) the median plane, below the left lobe or sometimes the quadrate lobe of the liver, and at the level of the first lumber vertebra, or the fibro-cartilage between this and the second lumbar. During distention it is pushed over beneath the quadrate lobe for a variable distance, but very rarely more than 1 or 2 inches to the right of the median plane. Its average position can be marked on the surface of the body by the intersection of two lines; one drawn horizontally half-way between the top of the sternum and the pubic crest (Addison), the other drawn vertically a little way (inch, 12 mm.) to the right of the median plane.
During the earlier stages of gastric digestion the sphincter pylori is strongly contracted and the aperture firmly closed, but it opens intermittently to allow of the passage of properly digested portions of the food. As digestion advances the sphincter probably relaxes somewhat but in hardened bodies a really patent pylorus is rarely or never found, which would seem to Pyloric sphincter Longitudinal muscular coat
FIG. 917.-LONGITUDINAL SECTION THROUGH THE PYLORIC CANAL AND COMMENCEMENT
indicate that the pylorus is normally closed, or nearly so, and that its opening is an active rather than a passive condition, as in the case of the anal canal.
As regards its size, the pylorus is stated to be about inch (12.5 mm.) in diameter, but there is no doubt that this represents neither its full size nor its calibre when at rest. Foreign bodies with a diameter of to 1 inch have been known to pass through the pylorus without giving rise to trouble, even in children. On the other hand, when at rest, with an empty stomach and duodenum, the aperture is practically closed.
Curvatura Ventriculi Minor. The lesser curvature is directed towards the liver, and corresponds to the line along which a fold of peritoneum called the hepato-gastric ligament is attached to the stomach, between the pyloric and œsophageal orifices (Fig. 916). The fold connects the stomach and liver, and between its two layers the gastric vessels run along the curvature of the stomach.
While the lesser curvature is, on the whole, concave, it consists of two portions which meet and form a sharp angle, called the incisura angularis, situated nearer the pyloric than the cardiac end, though its position varies with the condition of the stomach. The superior or left portion is nearly vertical, and continues the direction of the right margin of the oesophagus, while the inferior or right portion is more nearly horizontal, when viewed from the front. The depth and acuteness of the angle between these two segments varies with the degree of distension of the stomach. When the pyloric portion of the stomach is full, the inferior portion of the lesser
curvature becomes distended, and that portion of the border becomes convex in outline.
The lesser curvature does not form a straight line along the surface of the stomach, for at the left end it turns forwards somewhat on to the anterior surface of the stomach, to the place where the cardiac orifice is situated. In length, the lesser curvature measures some 3 to 4 inches.
Curvatura Ventriculi Major.-The greater curvature of the stomach is usually over three times as long as the lesser curvature, and corresponds to a line drawn from the cardia over the summit of the fundus (Fig. 916), and then along the most projecting portion of the stomach as far as the pylorus. In general, it is directed to the left and forwards, but at its beginning, near the cardia, it of course looks in a different direction. The great curvature corresponds in the greater part of its length to the attachment of the gastro-splenic
and gastro-colic ligaments, folds of peritoneum passing to the spleen and to the transverse colon respectively; and in close relation to it, between their layers, run the right and left gastro-epiploic vessels.
This border of the stomach, like the lesser curvature, does not present a uniformly curved outline. Towards the pylorus a notch is often found, called the sulcus intermedius. The portion Transverse to the right of this sulcus is known as the pyloric canal.
On the left side of this notch, the greater curvature bulges forwards, forming a chamber called the antrum pyloricum, and the projecting rounded prominence which it forms is, in some phases of digestion, marked off from the rest of the body of the stomach by a temporary indentation. Other indentations which are sometimes found on the greater curvature, or the body of the
colon Position of umbilicus
FIG. 918.-ABDOMEN OF FEMALE, SHOWING DISPLACEMENTS
RESULTING FROM TIGHT LACING.
stomach, are probably due to The liver is much enlarged, and extends on the left side to the
temporary peristaltic waves of contraction.
Paries Anterior.-The anterior surface of the stomach is
ribs, where it was folded back on itself for over an inch. The pyloric end of the stomach and the beginning of the duodenum are quite superficial below the liver, and all the viscera are displaced downwards. (From a photograph of a body hardened by injections of formalin.)
more convex and more extensive than the posterior. It lies, when the organ is distended, in contact with the inferior surface of the left lobe of the liver medially, the vault of the diaphragm laterally, and the anterior abdominal wall below (Fig. 916). When the stomach is empty, on the other hand, the transverse colon doubles up in front of it, and separates its anterior surface from the liver and diaphragm and abdominal wall.
Paries Posterior. The posterior surface looks downwards and posteriorly. It is more flattened than the anterior, and is moulded by the structures upon which it rests.
Thus, to the left is a flattened area, passing on to the fundus, which is in contact with the diaphragm and the spleen. To the right of the fundus, the posterior surface is divisible into two areas, lying in different horizontal planes, a superior and an inferior, separated by a slight ridge. The superior portion, nearly vertical, lies in contact with the left kidney and supra-renal gland and the diaphragm; and the inferior portion, more horizontal, is in contact with the pancreas,
transverse mesocolon, and transverse colon.
These structures constitute the
posterior wall of the bursa omentalis of the peritoneal cavity.
Between the two areas, the wall comes into contact with the splenic artery
as it runs along the superior border of the pancreas.
The different portions into which the stomach may be divided are as follows:
FIG. 919. THE VISCERA AND VESSELS ON THE POSTERIOR ABDOMINAL WALL. The stomach, liver, and most of the intestines have been removed. The peritoneum has been preserved on the right kidney, and also the fossa for the caudate lobe. When the liver was taken out, the vena cava was left behind. The stomach bed is well shown. (From a body hardened by chromic acid injections.)
Fundus Ventriculi.-The fundus is that portion of the stomach which lies above a horizontal plane drawn through the oesophageal opening. It is rounded or domeshaped. This shape seldom alters, whatever the condition of the stomach may be. It is usually filled with gas.
Corpus Ventriculi.-The body of the stomach extends from the fundus to
the incisura angularis on the lesser curvature, and to the notch on the greater curvature already described. It forms a rounded chamber, capable of great distension, but when the stomach is empty it contracts to a narrow tube-like structure. As the stomach is seldom completely empty, the body usually tapers from the fundus to the proximal end of the pyloric portion (Fig. 925).
Pars Pylorica. The pyloric portion of the stomach extends from the incisura angularis in the lesser curvature, and a variable and inconstant notch on the greater curvature, as far as to the pyloric orifice (Fig. 925).
It differs from the body of the stomach in being more tubular in shape, and possessing thicker walls.
It has been divided anatomically into two portions, the pyloric canal and the antrum pyloricum respectively.
The pyloric canal is a short more or less tubular portion rather more than an inch in length, extending from the sulcus intermedius on the greater curvature to the pyloric constriction. The proximal portion, called the pyloric antrum,
FIG. 920.-TRANSVERSE SECTION OF THE TRUNK AT THE LEVEL OF THE FIRST LUMBAR VERTEBRÆ. Showing relations of stomach, pancreas, kidneys, etc. From a subject ten years old.
is more expanded. It is not clearly demarcated from the body of the stomach by any constant line of division on the greater curvature. On the lesser curvature it extends from the incisura angularis to the pyloric canal, and it is occasionally pouched outwards on the side of the greater curvature so as to form a chamber or pouch, the "camera princeps" of His.
When the stomach has been removed, after the body has been hardened, a chamber or recess is exposed, known as the stomach chamber. It is (Figs. 920 and 921) a space in the upper and left portion of the abdominal cavity which is completely occupied by the stomach when that organ is distended, but into which the transverse colon also passes, doubling up in front of the stomach, when the latter is empty.
The chamber presents an arched roof, an irregularly sloping floor, and an anterior wall. The roof is formed partly by the visceral surface of the left lobe of the liver, and in the rest of
its extent by the left cupola of the diaphragm, which arches gradually downwards behind and on the left to meet the floor.
The floor or "stomach bed" (Fig. 921) is a sloping shelf on which the posterior surface of the stomach rests, and by which it is supported. The bed is formed posteriorly by the superior pole of the left kidney (with the supra-renal gland) and the gastric surface of the spleen; anterior to this, by the wide anterior surface of the pancreas; and more anteriorly still, by the transverse mesocolon running forwards above the small intestine, from the anterior edge of the pancreas to the transverse colon (Fig. 921), which completes the floor anteriorly.
Finally, the anterior wall of the stomach chamber is formed by the abdominal wall, between the ribs on the left and the liver on the right side.
This chamber is completely filled by the stomach, when that organ is distended. When, on the other hand, the stomach is empty and contracted, it still rests on the floor, or stomach bed, but occupies only the inferior portion of the chamber, whilst the rest of the space is filled by the transverse colon, which turns gradually upwards as the stomach retracts, and finally comes to lie both above and in front of that organ and immediately beneath the diaphragm-a fact to be remembered in clinical examinations of this region.
Peritoneal Relations.-The stomach is almost completely covered by
Facies anterior paucreatis
STOMACH CHAMBER VIEWED FROM THE FRONT AND FROM BELOW.
peritoneum the anterior surface being clothed by that of the general peritoneal sac, and the posterior surface by the anterior layer of the bursa omentalis (see p. 1162, From the lesser curvature the hepato-gastric ligament extends to the liver, whilst to the greater curvature the gastro-lienal and gastro-colic ligaments are attached Finally, a small peritoneal fold, known as the gastro-phrenic ligament, is found running from the stomach up to the diaphragm along the left side of the œsophagus.
A small irregularly triangular area (Fig. 919), about 2 inches wide and 1 inches from above downwards, during moderate distension of the stomach, on the posterior surface below and to the left of the cardia, is not covered with peritoneum, and over it the organ is in direct contact with the diaphragm, occasionally also with the superior extremity of the left kidney and the supr renal gland. From the left angle of this "uncovered area" the attachment of the gastro-lienal ligament starts; and at the right angle is the commencement of a fold through which the left gastric artery passes to the stomach. This fold is called the left gastro-pancreatic fold.
The right gastro-pancreatic fold is a fold of peritoneum passing from the right extremity of