Gastrointestinal System
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Digestive System
It can be helpful to think of the digestive system as a tube running through the body with an opening at each end, the mouth at the top and the anus at the bottom. The tube isn’t a neat, constant shape throughout its course. It swells into
Mouth and Esophageal Motility
Mastication, or chewing, mixes food with salivary mucus. This action subdivides food and exposes ingested starch to salivary amylase to begin the digestive process. Mastication is not essential for normal GI function but facilitates the process. Swallowing propels food from the mouth into the esophagus. The initiation
Gastric Motility
Stomach The stomach is anatomically and functionally divided into the fundus, body, and antrum. The fundus and body are highly distensible and act as reservoir for the ingested meal. A 1.5 L volume increase causes only a small increase in pressure in the lumen of the stomach.
Small Intestinal Motility
The small intestine is divided into duodenum, jejunum, and ileum, with the duodenum and jejunum being the major site of digestion and absorption. Chyme takes 2 to 4 hours to move through the 5 m of the small intestine. Segmentation, which mixes intestinal contents and enhances contact
Colonic Motility
The colon reabsorbs salts and water. About 1500 mL of fluid enters the colon each day, but only 50 to 100 mL of fluid is excreted in feces. Anatomically, the colon is divided into the cecum, ascending colon, transverse colon, and descending colon. Segmental contraction of the
