Human physiology . stine indicates that the functional adaptability of this organ,which is the principal factor in digestion, is much greater than weshould suppose a priori. VI. Owing to its muscular coats the intestine is an organ ofmovement, with the office of gradually driving forward the chyme 232 PHYSIOLOGY rilAi1. or alimentary pulp, in order to mix it with the digestive secretions,to facilitate the absorption of the products of digestion, and finallyto expel the undigested and imabsorbed residues of food, alongwith the excreta that collect in the gut. The several parts of the intestine,
Human physiology . stine indicates that the functional adaptability of this organ,which is the principal factor in digestion, is much greater than weshould suppose a priori. VI. Owing to its muscular coats the intestine is an organ ofmovement, with the office of gradually driving forward the chyme 232 PHYSIOLOGY rilAi1. or alimentary pulp, in order to mix it with the digestive secretions,to facilitate the absorption of the products of digestion, and finallyto expel the undigested and imabsorbed residues of food, alongwith the excreta that collect in the gut. The several parts of the intestine, morphologically speaking,show a gradual differentiation, from which a correlative differentia-tion of function may be argued. The duodenum is distinguishednot only by the absence of a mesentery, and by being only partiallycovered witli peritoneum, but also by presenting the widest andmost muscular part of the small intestine. Its total length variesbetween 25 and 30 cm., its breadth from approximately 35 to 50 FIG. 75.—Auerbachs plexus between the two muscular coats of the intestine. Gold chloride method. (Cadiat.) The remainder of the small intestine, which has a mesentery, isarbitrarily divided into jejunum (upper f) and ileum (lower f),which have no distinct morphological boundaries. But the portionbetween the commencement of the jejunum and the end of theileum (where the ileo-caecal valve is situated) gradually alters instructure and appearance, so that the two ends of the segmentcan be readily distinguished. The jejunum is larger and moremuscular; the ileum is narrower with thinner and paler coats, thevalvulae conniventes are smaller and gradually disappear at thelower end, the villi are shorter, the groups of Peyers patcheslarger and more numerous. Owing to all these differentialcharacters, any part of the jejunum weighs more than a corre-sponding portion of the ileum. The diameter of the jejunum isabout 325 cm., that of the ileum 260 cm. They vary consider-ably i
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectphysiology, bookyear1
