The stomach participates in all digestive activities except ingestion and defecation. It vigorously churns food. It secretes gastric juices that break down food and absorbs certain drugs, including aspirin and some alcohol. The stomach begins the digestion of protein and continues the digestion of carbohydrates and fats. It stores food as an acidic liquid called chyme, and releases it gradually into the small intestine through the pyloric sphincter.
body
mid-portion of the stomach
cardia
(also, cardiac region) part of the stomach surrounding the cardiac orifice (esophageal hiatus)
cephalic phase
(also, reflex phase) initial phase of gastric secretion that occurs before food enters the stomach
chief cell
gastric gland cell that secretes pepsinogen
enteroendocrine cell
gastric gland cell that releases hormones
fundus
dome-shaped region of the stomach above and to the left of the cardia
G cell
gastrin-secreting enteroendocrine cell
gastric emptying
process by which mixing waves gradually cause the release of chyme into the duodenum
gastric gland
gland in the stomach mucosal epithelium that produces gastric juice
gastric phase
phase of gastric secretion that begins when food enters the stomach
gastric pit
narrow channel formed by the epithelial lining of the stomach mucosa
gastrin
peptide hormone that stimulates secretion of hydrochloric acid and gut motility
hydrochloric acid (HCl)
digestive acid secreted by parietal cells in the stomach
intrinsic factor
glycoprotein required for vitamin B12 absorption in the small intestine
intestinal phase
phase of gastric secretion that begins when chyme enters the intestine
mixing wave
unique type of peristalsis that occurs in the stomach
mucosal barrier
protective barrier that prevents gastric juice from destroying the stomach itself
mucous neck cell
gastric gland cell that secretes a uniquely acidic mucus
parietal cell
gastric gland cell that secretes hydrochloric acid and intrinsic factor
pepsinogen
inactive form of pepsin
pyloric antrum
wider, more superior part of the pylorus
pyloric canal
narrow, more inferior part of the pylorus
pyloric sphincter
sphincter that controls stomach emptying
pylorus
lower, funnel-shaped part of the stomach that is continuous with the duodenum
ruga
fold of alimentary canal mucosa and submucosa in the empty stomach and other organs
stomach
alimentary canal organ that contributes to chemical and mechanical digestion of food from the esophagus before releasing it, as chyme, to the small intestine
Watch this animation that depicts the structure of the stomach and how this structure functions in the initiation of protein digestion. This view of the stomach shows the characteristic rugae. What is the function of these rugae?
Answers may vary.
1. Which of these cells secrete hormones?
A) parietal cells
B) mucous neck cells
C) enteroendocrine cells
D) chief cells
C
2. Where does the majority of chemical digestion in the stomach occur?
A) fundus and body
B) cardia and fundus
C) body and pylorus
D) body
A
3. During gastric emptying, chyme is released into the duodenum through the ________.
A) esophageal hiatus
B) pyloric antrum
C) pyloric canal
D) pyloric sphincter
D
4. Parietal cells secrete ________.
A) gastrin
B) hydrochloric acid
C) pepsin
D) pepsinogen
B
1. Explain how the stomach is protected from self-digestion and why this is necessary.
The mucosal barrier protects the stomach from self-digestion. It includes a thick coating of bicarbonate-rich mucus; the mucus is physically protective, and bicarbonate neutralizes gastric acid. Epithelial cells meet at tight junctions, which block gastric juice from penetrating the underlying tissue layers, and stem cells quickly replace sloughed off epithelial mucosal cells.
2. Describe unique anatomical features that enable the stomach to perform digestive functions.
The stomach has an additional inner oblique smooth muscle layer that helps the muscularis churn and mix food. The epithelium includes gastric glands that secrete gastric fluid. The gastric fluid consists mainly of mucous, HCl, and the enzyme pepsin released as pepsinogen.