Page:The New International Encyclopædia 1st ed. v. 10.djvu/808

* INTESTINE. 718 INTESTINE. feet 4 inches in llie fi-malc. With the exception o; the (iuoUcnuiii, the small inlfslino lies in gen- «>ral in the fciilral pmt uf llii' abdominal cavity, Ixiundvd liy the large intesliiu- on either side and above. The jejunum and ileum are connected to the posterior alidnminal wall liya rellcxion of the peritoneum, called (li<> mesentery. The duodenum is about 10 inches loiif;, 1 1^ to 2 inelies in diam- eter, and curved like a horseshoe. The head of the pancreas is received into the curve. It is the part of the intestine which is continuous with the stomach at its pyloric extremity. The jeju- num is descrilied under its title. The jejunum and ileum vary much in the arraiijrement of their coils, and there is little regularity in their posi- tion beyond that already stated. The term ileum is applied to the last three-fifths of the small gut. It ends at the ilco-o;peal valve, through which the contents of the small intestine escape into the head of the colon. The small intestine has four coats: Serous or peritoneal, nuiscular, areolar or submucous, and mucous. The last is covere<l with minute prolongations called 'villi.' and line<l with columnar epithelium. There are few vnl- vulw coiinivcntei, or folds of nuieous membrane, in the ileum. Solitary glands alone or in aggre- gations (called Peyer's patches) are found in the lower part of the ileum. These are largely obliterated in typhoid fever. The large inle-stine is divided into the ctecuni ; the ascending, transverse, and descending colon; the sigmoid flexure; and the rectum. It is so placed as to encircle the small intestine. The c.TCum lies in the hollow of flic riglit iliac region. Prom this point the eohm rises to the liver, then crosses the abdominal cavity to the opposite side, passing below the stomach to the spleen; then. making a sharp turn, it descends to the left iliac fossa, where it forms a loop termed the sigmoid flexure (from its resembling the old Greek letter sigma ) ; and finally, now termed the rectum, cur'es back to the head of the sacrum, thence follows the concavity of the sacrum, and thence curves backward to the anus. .Vltached to the ca>cum, generally back of it, is a small, short, blind tube, about ,S to 4 inches long, opening into the gut, and termed the vermiform appendix (q.v.). The subdivisions of the large intestine are treated under their own titles. The constant motion of the intestine (peristalsis), by which its contents are conveyed along, is due to the con- tractions of the muscular fibres of the gut. See Digestion. hi.stolooy. The wall of the intestine is composed of four distinct coats, which from without inward are known as: (1) The serous coat. (2) the muscular coat, (3) the submucous coat, and (4) the mucous coat or mucous membrane. These coats present certain dilTcrences in structure in the two main di'isions of the intestine, the small in- testine and the large intestine. TiTE Small Intestixk. The serous coat of the small intestine consists of a single layer of epi- thelium or endothelium (forming the peritoneal surface) resting upon a thin layer of delicate connective tissue. ISencath this lies the muscular coat composed of (a) an outer portion in which the smooth muscles arc disposed longitudinally to the long axis of the intestines and consc- <)uently known as the longitudinal muscular coat, and (b) an inner or circular coat in which the nuiscle-cclls are disposed transversely to the axis of the intestines. The two layers of muscle are separated by more or less connective tissue. The subnnieous coat consists of loosely arranged bun- dles of fibrous and elas- tic connective tissue, with a rich plexus of blood-vessels, lymphat- ies, and nerves. Through the submucous coal are distributed, at varying intervals, cir- cumscribed m:isses of 1 y m p h o i d tissue or lymph - nodules. These may occur singly (soli- tary glands, or folli- cles), lying in both sub- iiuieosa and mucosa, and may even jjrojeet slight Iv from the free LonKttudinal section of 111] III a II Hill nil liiU'Htliios, Hliiiwiiif; Kfiifrai iflatloii of ttit' foliirt foiiHtitiitliiK til** vnlvuliB coDDlventes to the IIIUCOHII mill HUbllllllMlllHIHIUt. The latter eonHtltiit''H tlio llbrouH core over wliU'h the niueosa with itit villi uiid glaiiils ext4.*nd8. surface of the mucous membrane. Or else, instead of a single nodule, there may be a collection of nodules forming what is known as Peyer's patches, which are SECTION OF ^MAI.L 1STE8TINE OP X CAT. n. Mucous rfmt; f>, siihniucoui* coat; c, muHciilnrcoat; d, fl, I'l-yer's piit^^h, cut cro8«wlne. found mainly in the ileum. Usually from 20 to 30 nodules constitute a patch. Like the solitary nodules, they lie in both submucosa and mucosa and often project upward to the free surface of the intestine. Finally, the mucous membrane of the small intestine is thrown up into transverse or ob- lique folds, which involve also the submucous coat, and which are known as the viilviilw ronniicnlcH. In addition to this the mucous membrane over the valvula; is studded with niinvite projections known as villi, which are characteri.stic of the small intestine. The mucous membrane consists of three coats, the epithe- lial coat, the stroma, and the niuscularis mucosa?. The epithelial coat is eom- po.sed of a single layer of columnar epithelium, which covers the surface of the mucous membrane. Dis- tributed at interi'als among the columnar epithelial ISaK*-' '"^"='* ■"■ cells are clear, transparent cells, which, on account of their shape, are called goblet cells, or, because of their secretion, mucous cells. The epithelium rests upon a basement membrane, beneath which lies the stroma. The Longitudinal section of villus friiiii InteMtiiie of dof;, tiiij^hly nia^riiitli'd. a, CoJuinliar epltlti'lium containing poblet r-eils, h. and iniKfatory leu- roevte«(/;j; c, basement nienibrniie; fj, plate-like connective tissue ele- ments of core; p. blood- vesselfl; /; absorbffiit