Digestive System Terms


Alimentary canal: The continuous muscular digestive tube extending from the mouth to the anus, which includes the oral cavity, pharynx, esophagus, stomach, small and large intestines, rectum, and anal canal.


Chief cell of stomach: A cell in the gastric glands that secretes pepsinogen, the precursor of the enzyme pepsin.


Cholecystokinin (CCK): Hormone secreted by enteroendocrine cells in the duodenum that stimulates secretion of pancreatic juice rich in digestive enzymes, and stimulates gallbladder contraction to release bile.


Chyme: The semifluid mass of partly digested food that is passed from the stomach into the duodenum.


Duodenal gland: Gland in the submucosa of the duodenum that secretes an alkaline mucus to help neutralize the acid in chyme, and protect the mucosa from the action of digestive enzymes. Also called Brunner's gland.


Enteroendocrine cell of intestine: A cell of the mucosa of the small intestine that secretes the hormones cholecystokinin (CCK) and secretin.


Enteroendocrine cell of stomach: A cell in the gastric glands of the pyloric antrum of the stomach that secretes the hormone gastrin. Also called G cells


Epiglottis: Elastic cartilage at the back of the throat that covers the opening of the larynx during swallowing.


Esophagus: The gullet; a hollow muscular tube that connects the pharynx to the stomach.


Gallbladder: A pear-shaped organ on the inferior surface of the liver that stores and concentrates bile until needed for digestion; it contracts and releases bile into the duodenum when stimulated by cholecystokinin.


Gastric glands: Glands in the mucosa of the stomach composed of cells that empty their secretions into narrow channels called gastric pits.


Gastrin: Hormone secreted by enteroendocrine cells in the stomach that increases gastric motility, and stimulates parietal cells to increase HCl secretion.


Gastrointestinal tract: The stomach, small intestine, and large intestine. Also called GI tract or digestive tract.


Ileocecal sphincter: Valve at the junction of the small and large intestines.


Large intestine: The terminal portion of the GI tract, extending about 1.5 meters (5 feet) from the ileocecal valve to the anus; it comprises the cecum, colon, rectum, and anal canal; it absorbs water and electrolytes to produce feces.


Liver: The largest gland in the body; it produces and secretes bile to help digest fat; it receives and detoxifies most absorbed nutrients through the hepatic portal vein; it stores glycogen; it serves in the metabolism of protein, carbohydrate, and fat.


Mesenteries: Double-layered extensions of the peritoneum that support most organs in the abdominal cavity, and suspends the small intestine from the posterior body wall; retroperitoneal organs are found posterior to the mesentery, lying against the dorsal abdominal wall.


Oral cavity: The cavity with boundaries of the lips, cheeks, palate, and tongue; lined with stratified squamous epithelium; it functions in the mechanical breakdown of food and begins chemical digestion of carbohydrates.


Pancreas: A retroperitoneal gland located behind the stomach, between the spleen and the duodenum; its exocrine function is to secrete pancreatic juice with digestive enzymes and bicarbonate ions into the duodenum; its endocrine function is to secrete insulin, glucagon, somatostatin, and pancreatic polypeptide into the blood.


Parietal cell: A cell in the gastric glands that secretes hydrochloric acid (HCl) and intrinsic factor.


Peristalsis: Progressive, wave-like contractions that move foodstuff through the alimentary tube organs, or that move other substances through other hollow body organs.


Peritoneum: Serous membrane lining the interior of the abdominal cavity and covering the surfaces of abdominal organs; the visceral peritoneum covers the external surfaces of most of the digestive organs, the parietal peritoneum lines the body wall of the abdominopelvic cavity, and the peritoneal cavity is the space in between that is filled with serous fluid; the lesser omentum extends from the liver to the lesser curvature of the stomach and the first part of the duodenum; the greater omentum descends from the greater curvature of the stomach and hangs down like an apron, anterior to the intestines.


Pharynx: The throat; a muscular tube that starts at the internal nares and runs partway down the neck, where it opens into the esophagus posteriorly and the larynx anteriorly; it is subdivided into the nasopharynx which is lined with ciliated pseudostratified columnar epithelium with goblet cells, and the oropharynx and laryngopharynx which are both lined with stratified squamous epithelium.


Pyloric sphincter: Valve that controls food movement from the stomach into the duodenum.


Salivary Glands: The largest glands of the oral cavity that secrete saliva containing acidic salt water, mucus, salivary amylase, lingual lipase, and the antimicrobial agents IgA, lysozyme and defensins; the paired parotid glands are inferior and anterior to the ear and secrete seromucous saliva through the parotid ducts; the paired sublingual glands are in the floor of the mouth beneath the tongue and secrete seromucous saliva through the sublingual ducts; the paired submandibular glands are in the neck and secrete seromucous saliva through the submandibular ducts.


Secretin: Hormone secreted by enteroendocrine cells in the duodenum that stimulates the secretion of pancreatic juice rich in bicarbonate ions, and stimulates the liver to increase bile output.


Segmentation: Localized mixing contractions in the intestine, which mix chyme with digestive juices.


Small intestine: The middle portion of the GI tract, extending about 6 meters (20 feet) from the pyloric valve to the ileocecal valve; it comprises the duodenum, jejunum, and ileum; it mixes food with pancreatic juice and bile for the final enzymatic breakdown of food molecules; it is the main site of nutrient absorption.


Stomach: The large, J-shaped digestive sac between the esophagus and the duodenum; it secretes hydrochloric acid and pepsin to begin the chemical breakdown of proteins and convert food into chyme; it comprises the cardiac region, fundus, body, and pyloric region.


Villi: Finger-like projections of the small intestinal mucosa that greatly increases its surface area for absorption.