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 Temporary food storage  mechanical and chemical breakdown of food ◦ Pepsin is secreted to break down protein  chyme (processed food) is the end result ◦ A combination of digestive enzymes, pepsin, HCl ◦ Sent to the small intestine © 2015 Pearson Education, Inc.

 C-shaped organ - left side of abdominal cavity  Sphincters control openings: ◦ Food enters at cardioesophageal sphincter ◦ Food exits at pyloric sphincter (valve)  Regions of the stomach: ◦ Cardial part (cardia)—near the heart ◦ Fundus—expanded portion lateral (left) to the cardiac region ◦ Body—midportion ◦ Pylorus—funnel-shaped terminal end © 2015 Pearson Education, Inc.

Esophagus Cardia Fundus Serosa Body Rugae of mucosa Pyloric sphincter (valve) Pylorus (a)

Fundus Body Rugae of mucosa Pyloric sphincter (b)

 Rugae allow stomach stretch  internal folds of the mucosa  present when the stomach is empty  Muscularis externa has a third oblique layer ◦ helps to churn, mix, and pummel the food © 2015 Pearson Education, Inc.

Esophagus Cardia Fundus Serosa Body Rugae of mucosa Pyloric sphincter (valve) Pylorus Oblique layer Circular layer Longitudinal layer Muscularis externa (a)

 lined with simple columnar epithelium  In addition, it contains ◦ gastric pits  house gastric glands  secrete gastric juice ◦ mucous cells produce bicarbonate-rich alkaline mucus that protect the stomach wall © 2015 Pearson Education, Inc.

 Gastrin – which promotes production of: ◦ Enzymes that break down proteins:  Pepsin  Rennin (present in infants) ◦ Hydrochloric Acid ◦ Intrinsic factor (a glycoprotein)- needed for vitamin B 12 absorption in the small intestine  Regulated by neural and hormonal factors  Most chemical digestion occurs in the pyloric region

Figure 14.4c Anatomy of the stomach. Pyloric sphincter Gastric pits Gastric pit Gastric gland Surface epithelium Parietal cells (secrete HCL) Gastric glands Chief cells Produce pepsinogen (pepsin ) Enteroendocrine cells (secrete gastrin)

 Food propulsion 1.Peristalsis: waves of peristalsis force food past the pyloric sphincter 2.Grinding: The pylorus regulates the flow of chyme into the small intestine 3 ml at a time  Retropulsion: peristaltic waves close the pyloric sphincter  this forces contents back into the stomach.  the stomach empties in 4–6 hours depending on meal quality  High fat = slow digestion © 2015 Pearson Education, Inc.