ANATOMY AND PHYSIOLOGY. THE stomach, the widest and most dilatable part of the alimentary canal, has a form which varies somewhat in different individuals. Removed from the body, and moderately distended, it generally takes the shape here represented (Fig.1)—a shape best described as that of a bent cone, the concave aspect of which receives a tube at one fourth of the distance from its base. In it we distinguish an anterior and a posterior surface; a superior and an inferior border; a right and a left extremity; and lastly, the cardiac and pyloric apertures, by which it communicates with the oesophagus and duodenum respectively, and thus becomes continuous with the remainder of the digestive canal. The description of these parts varies with the state of the organ. Thus, when empty and uncontracted, the stomach is flattened vertically; its anterior and posterior surfaces touching each other, while its upper and lower margins really deserve the title of " borders." But when the organ is distended, any transverse vertical section becomes almost a circle, its borders and surfaces merging into each other. Its uppermost part, however, is still distinguishable as the lesser curvature (a, e, b, Fig. 1), and its lower as the greater curvature (g, d, f, c, b). The general concavity of the former curve is especially marked in its first three-fifths, at the end of which part (e) it usually becomes slightly convex. A shallow notch (c) often divides the greater curvature into two portions opposite this point, and, with the latter, defines the commencement of the pyloric pouch (c, b, b, e). The cardiac pouch, great or splenic extremity (d) is the part to the left of the cardia or œsophageal opening (a), beyond which it projects for about three inches. At this aperture the œsophagus dilates gradually, so as to resemble an inverted funnel. To the right of the oesophagus, the stomach expands slightly, to reach its maximum diameter at about the Stomach, as seen by inflating it, and dissecting off its peritoneum, its longitudinal, and part of its transverse, muscular coat. a, g, Cardia; b, b, pylorus; a, e, b, lesser curvature; g, d, f, c, b, greater curvature; g, d, to near f, cardiac sac; c, b, b, e, pyloric sac. (Above a, g are seen the transverse fibres of the oesophagus; and below these, the uppermost of the oblique fibres of the stomach, passing towards c. Covering the pyloric sac are seen the transverse fibres. The dotted line, a, e, b, shows how extreme distension of the stomach tends to affect the lesser curvature.) middle of the organ (f). Beyond this point it tapers away to the pylorus (b, b), where a sudden constriction marks the site of the valve. The dimensions of the organ are even more variable than its form. In the healthy middle-aged male, the moderately distended stomach is about thirteen to fifteen inches long; and its diameter, at the widest part five, near the pylorus two, inches. Its total surface is about one and a quarter square feet; its capacity about 175 cubic inches, or five pints; its weight seven ounces.' The attachment of the stomach is effected chiefly by the continuity of its extremities with the more fixed duodenum 1 For women and children, these estimates require a proportionate reduction. They are increased by habitual distension, and by the relaxation of old age; diminished by habitual exercise, or by the practice of taking very small meals (as in dilative emphysema of the lungs). and œsophagus. The former tube is connected with the posterior wall of the belly; the latter perforates the diaphragm, so as to enter the abdomen about one inch in front of the left border of the aorta, by an aperture which is everywhere muscular, though close to the posterior border of the tendon. The fixation of the stomach is also aided by certain processes of peritoneum. To the left of the œsophagus, the short phrenogastric omentum passes from the diaphragm to the cardiac pouch, which it reaches somewhat posteriorly. Still lower down, the stomach is united to the spleen by the gastro-splenic omentum. The lower border of the organ gives off the great omentum; this descends for some distance towards the bottom of the belly, and is then reflected upwards to the anterior border of the transverse colon, which it splits to enclose. The upper border of the stomach is attached by means of the gastro-hepatic or small omentum, which descends from the transverse fissure of the liver. All of these folds are double; though the four layers of the reflected omentum majus are often inseparably united to each other. Situation-The stomach is placed almost transversely in the upper part of the abdominal cavity, in which it passes from the left to the right side, as well as downwards, and slightly forwards. This direction results from its situation relatively to the œsophagus and duodenum; since it is joined by the former at its highest part, and near its left extremity, while the latter is immediately prolonged from its right or pyloric end. In this course from left to right, the stomach successively occupies the left hypochondriac and the epigastric regions; and, just at its termination, it reaches the right hypochondrium. Its anterior surface is therefore in contact with the diaphragm, where this muscle lines the cartilages of the left false ribs, and with the wall of the abdomen. Its posterior surface lies upon the pancreas, the aorta, and the crura of the diaphragm, where these parts cover the spine. Its left extremity is in contact, above, with the diaphragm; below with the spleen; and, posteriorly, it reaches the left supra-renal capsule and kidney. Its upper border is in apposition to the liver; viz., to its left lobe, to the lobulus Spigelii, and to part of the lobulus quadratus. Its lower border is parallel, and close to, the transverse colon. |