Book 4 - Self Instructional Manual for Cancer Registrars - SEER ...

The organs of the digestive system perform the vital function of altering the food so that it canbe used as nourishment by the body cells. The process of changing the chemical and physicalcomposition of food so that it can be utilized by the body is called digestion. The digestive systemprovides the source of energy required for growth, maintenance, and function of the body. Thisenergy is derived from the assimilation of food by the cells of the body through a series of chemicalreactions called metabolism.The walls of most of the organs of the gastrointestinal tract are made up of three main layers oftissue:• A mucous lining called the mucosa. It consists of a surface epithelium, a lamina propria, and,in most of the length of the GI tract (lower esophagus, stomach, small intestine, colon, and rectum),a muscularis mucosae.° A submucosa of connective tissue in which are embedded blood and lymph vessels• A muscularis propria or muscular layerMost of the organs have a serosa or covering layer of visceral peritoneum which invests the organto a varying extent depending on the particular segment of the organ and its mesenteric attachments.The cecum, transverse colon and sigmoid are almost completely invested with peritoneum, while theascending colon and descending colon are covered only on their anterior surfaces. The posteriorportions of these two segments of the colon are covered by loose areolar tissue.Study the diagram below carefully so that you will recognize the names of the various tissue layersof the organ wall. The depth of invasion of a neoplasm into the various layers of the wall is animportant measure of the spread of the tumor. You will utilize this information in Book 6 when youstudy extent of disease and the staging of malignant tumors.Figure 20. STRUCTURE OF INTESTINAL WALLMuse tar m m o ae I,_',_,'_,W_ ,'?%z'_._'tff._d_• " , '"? "."" "'_' . ......' "?'.,/.i,;j _ _vma.rJ ., "."' "'"" _"" 'to )-_""_"J• _ :'.".'_'_":_"I. -" _'j "MuseulLar|s proprJLa : , • , . ' .... :; ....... = o- _,," o, ,Longlt_dknst Layer _ '_ =-_eroma