The large Intestine is the site for absorption of water and elimination of solid waste. It contains the typical layers of the GI tract: mucosa, submucosa, muscularis externa and adventitia/serosa. The large intestine mucosa contains crypts, but no villi, and the lining epithelium is similar to that of the small intestine, containing simple columnar absorptive epithelial cells (colonocytes) and many goblet cells. The three regions (cecum, colon, and rectum) of the large intestine are similar histologically.

• Examine this section of colon, and identify the major layers and sublayers. Note that the muscularis externa of the large intestine differs from that of the small intestine because it contains an outside layer of three longitudinally oriented bands of smooth muscle, the teniae coli. Locate the myenteric plexi, which are distinct on this slide. The mucosa and submucosa are highly folded in this specimen. The mucosa is invaginated into many straight, tightly packed colonic glands, lined by columnar mucus-secreting cells. In the lumen, note the solid waste and indigestible material covered with mucus.

• Next, examine the images at the right and these two slides of colon at higher magnification (sample 1, sample 2). Locate the simple tubular colonic glands cut transversely. Note their small lumens, the lining epithelium containing colonocytes (C) or columnar absorptive cells and mucus-secreting goblet cells (G), and the many lymphocytes and capillaries in the surrounding lamina propria (LP).

• Examine the appendix in the images below and on these two slides (sample 1, sample 2) Note that its histology is similar to the rest of the large intestine, but that it contains abundant lymphatic nodules (LN).

• Finally, examine this specimen of the anal canal, noting its stratified squamous, keratinized epithelium and the smooth muscle of the internal anal sphincter and striated muscle of the external anal sphincter.
  
   

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