The digestive tract is a long, continuous tube of varying diameter extending from the lips to the anus. It includes oral cavity,esophagus, stomach, small intestines, large intestine and appendix. The oral cavity The oral cavity is lined by mucosa. There are a tongue and 32 permanent teeth in the oral cavity.

Fig ． 1 ．

Fig ． 2 ．

Except the oral cavity, the wall of the digestive tract consists of four layers: mucosa, submucosa, muscularis and adventitia. The mucosa consists of epithelium, lamina propria and muscularis mucosa.

Fig ． 3 ． Cross section of esophagus(HE stain,low mag.) Tunica muscularis submucos a mucosa

Fig ． 4 ． Stomach (HE stain,low mag.) mucos a submucos a Tunica musculari s

Fig ． 5 ． Stomach(HE stain,high mag.) Gastric pit Gastric gland

Parietal cell Neck mucous cell Fig ． 6 The mucosa of gastric fundus : fundic glands

Fig 7 ． Parietal cell Active cell Resting cell

Fig ． 8 parietal cell

Chief cells Fig ． 9 The mucosa of gastric fundus : fundic glands

Fig ． 10 Chief cell ZG: Zymogen granules

The small intestines include duodenum, jejunum and ileum. There are plica circulares and villi on the mucosa of the small intestines.

Villus Fig ． 11 Small intestine (jejunum)

Striated border Fig ． 12 Villus of small intestine(HE stain,high mag.) Central lacteal Goblet cell Columnar cell

Fig ． 13 Villus of small intestine(HE stain,high mag.) Central lacteal Striated border

Fig ． 14 absorptive cell

Fig ． 15 small intestine gland Paneth cell: acidophilic granules

Fig ． 16 Paneth cell: Secretory granules

Fig ． 11 Longitudinal section of Colon(HE stain,low mag.) Tunica muscularis mucosa submucosa

Intestinal gland epithelium Fig 12 Mucosa of Colon (HE stain,high mag.)

Fig 13 Mucosa of Colon (HE stain,high mag.) Intestinal gland

Fig ． 14 Cross section of appendix(HE stain,low mag.) Arrowhead:lymphoid nodule Intestinal gland muscularis mucosa