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the superior part of the pancreas to the first part of the duodenum. It encloses the hepatic artery.
Size and Capacity of the Stomach.-Probably no organ in the body varies more in size within the limits of health than the stomach. Moreover, as its tissues change so rapidly after death, measurements made on softened and relaxed organs are not only worthless but quite misleading. Consequently it is difficult, perhaps impossible, to arrive at a correct estimate of its size and capacity.
The length of the stomach in the fully distended condition is about 10 to 11 inches (25 to 27.5 cm.), and its greatest diameter not more than 4 to 4 inches (10 to 11.2 cm.); whilst its capacity in the average state rarely exceeds 40 ounces, or 1 quart.
FIG. 922. THE COURSE OF THE LARGE INTESTINE. The jejunum and ileum have been removed.
The length has been estimated by different authorities at from 10 to 13 inches (26 to 34 cm.); its diameter, from 3 to 6 inches (8 to 15 cm.); and its capacity from 1 to 5 pints. The measurements of the capacity given by Dr. Sidney Martin are probably the most accurate he states that the capacity varies between 9 and 59 oz., with an average of from 35 to 40, or a little over a litre.
The distance in a direct line from the cardiac to the pyloric orifice varies from 3 to 5 inches (75 to 125 cm.), and that from the cardia to the summit of the fundus from 2 to 4 inches (6-2 to 100 cm.).
As regards the weight, the average of twelve wet specimens freed from their omenta was found to be 4 oz. (135 grms.), with a maximum of 7 oz. (19845 grms) and a minimum of 3 cz. cz. (99-22 grms.). Glendinning gives the weight as 4 oz.
In the child at birth the stomach is scarcely as large as a small hen's egg, and its capacity is about 1 oz. (28-3 grms.). In shape it corresponds pretty closely to that of the adult, and the fundus is well developed. It is vertical in position.
Displaced Stomach (Fig. 918).-As a result of disease, or of constriction of the superior part of the abdomen, the stomach is occasionally displaced in position and distorted. in shape, so that instead of running obliquely forwards, downwards, and to the right, it is placed nearly vertically along the left side of the vertebral column, in which direction it has a very considerable length. Its inferior part bends rather suddenly, and runs upwards
and to the right to join the pylorus, which is often placed quite superficially below the liver. As a result of the displacement, the left extremity of the pancreas is pushed downwards from the horizontal until it almost assumes a vertical position. The narrowing and inversion of the inferior margin of the thoracic framework at the same time constricts the stomach about its middle, and may lead to a bilocular condition.
Hour-glass or Bilocular Stomach.-This is a condition of the organ, by no means rare, in which the stomach is more or less completely separated into two divisions-a cardiac and a pyloric-the normal arrangement in certain rodents and other animals. As a rule the former division is the larger, but occasionally the two are nearly equal, or the pyloric portion may exceed the cardiac in size. Sometimes the condition is temporary, and the result of a vigorous contraction of the circular muscular fibres at the seat of constriction. In other cases it is
permanent, and may be due to cicatricial contraction after gastric ulcer, or to some other pathological condition. The condition is more frequent in the female than the male, and is rarely found in the foetus or child.
Position of the Stomach.-When empty, or nearly so, the stomach lies in the left hypochondrium and left part of the epigastrium, with its fundus directed posteriorly towards the diaphragm, its long axis lying almost in a horizontal plane and its pyloric part running to the right to join the duodenum. In this state the whole organ is narrow and attenuated, particularly the pyloric part, which is contracted, and resembles a piece of thick-walled small intestine.
When distended, both the cardiac and pyloric parts become full and rounded (Fig. 923). It still lies within the hypochondriac and epigastric regions; but in exceptional cases, or in extreme distension, it may pass down below the subcostal lane and reach into the umbilical and left lumbar regions. As a result of the
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general increase in length which takes place during distension, the pylorus is moved a variable distance to the right beneath the quadrate lobe of the liver, and at the same time the long axis of the whole organ becomes much more oblique, running forwards, downwards, and to the right. Finally there is developed a special dilatation of the pyloric part, known as the antrum pyloricum, which in extreme distension is carried so far to the right that it may even reach to the hypochondrium.
Shape and Position of the Stomach as seen by X-Ray Examination.-Examination of the stomach by means of X-rays after a "bismuth meal" has given important information about the shape and position of the stomach in the living, and about the changes which occur as the stomach fills and empties.
These examinations corroborate, in great part, the conclusions which have been arrived at by the study of formalin specimens so far as the shape of the stomach, and its division into parts, is concerned. In regard, however, to the position and direction of the stomach, X-rays show that the stomach in the living, and especially in the erect attitude, is more vertical than it is after death, and when the body is examined in the horizontal position. In the upright position, in fact, the long axis of the organ appears to be nearly vertical. The general shape and position of the stomach in the vertical position, moderately distended, is shown in Fig. 923. From this it will be seen that not only is the body of the stomach nearly vertical, but that the greater curvature reaches down to the umbilicus, and may descend even beyond it. The pyloric part is directed upwards, as well as backwards, and the pylorus is not usually the lowest point of the stomach.
The other anatomical features of the stomach described above are well brought out. Thus the fundus is a hemispherical dome, lying to the left of the terminal portion of the œsophagus, and continuous in outline with the body of the stomach. It usually contains gas, and appears translucent to X-rays. The body is of uniform outline, and the pyloric part is marked off from it by the incisura angularis, on the lesser curvature. Further, the pyloric part shows division into pyloric antrum and pyloric canal. The incisura angularis and sulcus intermedius are distinct.
The position of the stomach is greatly influenced by attitude and by the condition of the abdominal muscles. Contraction of the abdominal muscles can elevate the stomach from 5 to 13 cm., or 2 to 5 inches, and the change from the horizontal to the erect attitude alters the height of the inferior border from 2 to 10 cm. This sinking which occurs in the alteration from the horizontal to the erect attitude, accounts largely for the differences found between the stomach seen in the postmortem room or on the operating table and the stomach displayed by means of X-rays. Thus, if the stomach figured on p. 1167 be considered fixed at the cardiac end, and somewhat fixed at the pylorus, and the pyloric antrum and greater curvature should sink downwards, the shape, as seen from the front, would closely resemble the X-ray appearances found often in the living.
The empty stomach is a contracted tubular organ, except at the fundus, where it appears to be always dilated. When food is taken, when the individual is standing or sitting, it runs down to the point where the gastric walls are in contact with one another. The distal portion of the stomach dilates for some distance, or at least as far as the pyloric canal.
As the stomach becomes filled the whole of the body of the organ becomes dilated, but the fundus and cardiac portion more particularly so, and these two latter regions act as a storehouse.
There is no definite division of this portion from the remainder of the stomach by a permanent sphincter, but the peristaltic waves of contraction begin about the middle of the organ, and form a fleeting constriction between the two parts.
As peristalsis goes on, the tubular pyloric part relaxes somewhat. The waves of peristalsis here become so deep as to divide this portion into chambers. The food substances are forced through the pylorus by successive waves of peristalsis, and in the form, usually, of jets which impinge against the posterior aspect of the duodenal wall.
Should there be undigested masses, the pyloric valve relaxes to allow them also to pass into the duodenum.
STRUCTURE OF THE STOMACH.
The stomach wall is composed of four coats-namely, from without inwards: (1) Tunica serosa, (2) tunica muscularis, (3) tela submucosa, and (4) tunica mucosa (Fig. 924). Tunica Serosa. The serous coat is formed of the peritoneum, the relations of which to the stomach have already been described. It is closely attached to the subjacent muscular coat, except near the curvatures, where the connexion is more lax; and it confers on the stomach its smooth and glistening appearance.
Tunica Muscularis.-The muscular coat, which is composed of unstriped muscle, is thinnest in the fundus and body, much thicker in the pyloric portion, and very highly developed at the pylorus. It is made up of three incomplete layers-an external, stratum longitudinale; a middle, stratum circulare; and an internal of oblique muscular fibres, fibræ obliqua.
The stratum longitudinale consists of longitudinal fibres, continuous with those of the œsophagus on the one hand, and those of the duodenum on the other (Fig. 926, A). They are most easily demonstrated on the lesser curvature, where they can be traced down from the right side of the œsophagus. Over the greater curvature and on the two surfaces they are present as an extremely thin and irregular sheet. Towards the pylorus the longitudinal fibres grow much thicker, and also much tougher and more closely united, and they take part in the formation of the pyloric valve.
A specially condensed band of these can be often made out both on the front and back at the antrum pyloricum, the form of which is said to be due to their presence. These bands are known as the ligamenta pylori (pyloric ligaments).
FIG. 925.-MUSCULAR COAT OF THE STOMACH, seen from within after removal of the mucous and submucous layers. The anterior half of the stomach is shown, viewed from behind (Cunningham).
The stratum circulare is composed mainly of circular fibres, continuous with the more superficial of the circular fibres at the lower end of the oesophagus (Fig. 925). They begin as a set of U-shaped bundles which loop over the lesser curvature at the right of
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the cardia, and pass downwards and to the left on both surfaces. Further to the right these looped fibres are succeeded by circles which surround the organ completely. Traced towards the narrow end of the stomach, the circular bundles grow thicker, and at the pylorus they undergo a further increase, giving rise to the pyloric sphincter which surrounds the orifice as a thick muscular ring.
The fibre obliqua, forming the inner layer, consist of fibres which are arranged on the fundus and adjacent parts of the stomach, in much. the same manner as those of the middle layer are on the body and pyloric part of the organ (Fig. 926, C). They are continuous above with the deeper circular fibres of the inferior end of the oesophagus, and form U-shaped bundles which loop over the stomach immediately to the left of the cardia, and run very obliquely downwards and to the right for a considerable distance on both surfaces of the organ. These looped fibres, as they pass to the left, gradually become less oblique, and finally form circles which surround the wide end of the stomach completely, even as far as the summit of the fundus. The oblique fibres can be most readily shown by removing the circular fibres on either surface below the cardia. When traced towards the right, they will be found to terminate by turning down and joining the fibres of the circular layer.
Tela Submucosa. The submucous coat is a layer of strong but loose connective tissue, which lies between and unites the muscular and mucous coats (Fig. 924). It is more loosely attached to the muscular and more closely to the mucous coat, and it forms a bed in which the vessels and nerves break up before entering the mucous membrane.
Tunica Mucosa.-If examined in the fresh state soon after death, the mucous coat is of a reddish-gray colour and of moderate consistence. When examined some time after death, the colour turns to a darker gray, and the whole membrane becomes softer and more pulpy. It is thicker (over 2 mm.) and firmer in the pyloric than in the cardiac part, and is thinnest at the fundus, where it often shows signs of post-mortem digestion. When the stomach is empty all three outer coats, which are extensile, contract; whilst the inextensile mucous coat, as a result of its want of elasticity, is thrown into numerous prominent folds or ruga, which project into the interior and, as it were, occupy the cavity of the contracted organ. These are, in general, longitudinal in direction, with numerous cross branches, and they are largest and most numerous along the greater curvature. They disappear when the stomach is distended.
When the surface of the mucous coat is examined in a fresh stomach, it is seen to
926. THE THREE LAYERS OF THE MUSCULAR COAT OF THE STOMACH. A, External or longitudinal layer; B, Middle or circular layer; C, Internal or oblique layer. a, Longitudinal fibres of oesophagus; b, Superficial circular fibres of esophagus passing into circular fibres of stomach in B; c, Deep circular fibres of esophagus passing into oblique fibres of stomach in C; d, Oblique fibres forming rings at the fundus; e, Submucosa.