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The Digestive System
Chapter 19
| Term | Definition |
|---|---|
| gastrointestinal (GI) tract | A continuous tube that extends from the mouth to the anus |
| accessory digestive organs | Teeth,tongue, salivary glands, liver, gallbladder, and pancreas |
| ingestion | This process involves taking foods and liquids into the mouth (Eating) |
| secretion | Each day, cells within the walls of the GI tract and accessory organs secrete a total of about 7 liters of water, acid, buffers, and enzymes into the lumen of the tract |
| mixing and propulsion | alternating contraction and relaxation of smooth muscle in the walls of the GI tract mix food and secretions and propel them toward the anus. (Motility) |
| digestion | Mechanical and chemical processes break down ingested food into small molecules |
| mechanical digestion | the teeth cut and grind food before it is swallowed, and then smooth muscles of the stomach and small intestine churn the food |
| chemical digestion | the large carbohydrate, lipid, protein, and nucleic acid molecules in food are broken down into smaller molecules by digestive enzymes |
| absorption | the entrance of ingested and secreted fluids, ions, and small molecules that are products of digestion into the epithelial cells lining the lumen of the GI tract |
| defecation | wastes, indigestible substances, bacteria, and cells shed from lining of the GI tract, and digested materials that were not absorbed leaved the body through the anus |
| mucosa, submucosa, muscularis, and serosa | four layers of the GI tract |
| mucosa | A layer of epithelium, areolar connective tissue (propia), smooth muscle (lamina muscularis mucosae) that increases surface area for digestion and absorption and protects GI against pathogens |
| submucosa | Areolar connective tissue that binds the mucosa and muscularis |
| muscularis | skeletal muscle that forms the external anal sphincter, mouth, pharynx, and upper esophagus |
| serosa and peritoneum | membrane that secretes a slippery, watery fluid that allows the tract to glide easily against other organs |
| greater omentum | drapes over the transverse colon and small intestine like a "fatty apron" |
| mesentery | A part of the peritoneum that binds the small intestine to the posterior abdominal wall |
| oral cavity | cheeks, hard and soft palates, and tongue |
| hard palate | consists of the maxillae and palatine bones, forms most of the roof of the mouth |
| soft palate | muscles in the mouth |
| uvula | projections of the soft palate, prevents entry of food and liquids into the nasal cavity |
| lingual frenulum | a fold of mucous membrane in the midline of the undersurface of the tongue, limits the movement of the tongue posteriorly |
| papillae | projections on the upper surface and sides of the tongue |
| parotid, submandibular, sublingual | 3 salivary glands |
| parotid glands | located inferior and anterior to the ears between the skin and masseter muscle |
| submandibular glands | found in the floor of the mouth |
| sublingual glands | beneath the tongue and superior to the submandibular glands |
| saliva | 99.5% water, 0.5% solutes. Water helps dissolve foods so they can be tasted and begins digestion. Solutes begin digestion of starches in the mouth |
| salivary amylase | breaks down starch in the mouth |
| salivation | secretion of saliva |
| mastication | mechanical digestion consisting of chewing |
| bolus | end product of mastication |
| pharynx | a funnel-shaped tube that is composed of skeletal muscle and lined by mucous membrane |
| esophagus | a muscular tube lined with stratified squamous epithelium, transports food to the stomach and secretes mucus |
| upper esophageal sphincter and lower esophageal spincter | 2 sphincters at the end of the esophagus |
| upper esophageal sphincter | regulates movement of food from the pharynx into the esophagus |
| lower esophageal sphincter | regulates movement of food from the esophagus to the stomach |
| voluntary, pharyngeal, and esophageal | 3 stages of swallowing |
| voluntary stage | bolus is forced to the back of the mouth cavity and into the oropharynx by the movement of the tongue |
| pharyngeal stage | breathing is temporarily interrupted when the soft palate and uvula move upward to close off the nasopharynx and the epiglottis seals of the larynx |
| esophageal stage | food is pushed through the esophagus by peristalsis |
| peristalsis | muscular contractions along the esophagus |
| stomach | mixing chamber and holding reservoir |
| rugae | large folds of the mucosa |
| mucous neck cells | secrete mucus |
| chief cells | secrete pepsinogen |
| pepsinogen | inactive form of pepsin |
| parietal cells | produce hydrochloric acid which kills microbes and converts pepsinogen into pepsin |
| gastric juices | the secretions of the mucous, chief, and parietal cells |
| G cells | secrete the hormone gastrin |
| mixing waves | gentle, rippling peristaltic movements of the muscularis |
| chyme | bolus mixed with gastric juices |
| gastric emptying | mixing wave forces a small amount of chyme through the the partially closed pyloric sphincter into the duodenum |
| pancreatic duct | secretions pass from the the pancreas to the duodenum; unites the common bile duct from the liver and gallbladder, forming a common duct to the duodenum |
| acini | pancreatic cells arranged in clusters, exocrine |
| pancreatic juice | cells within acini secrete a mixture of fluid and digestive enzymes, contains water, salt, sodium bicarbonate, and enzymes |
| pancreatic islets | 1% of the other pancreatic cells, endocrine. Secrete glucagen, insulin, somastatin, and pancreatic polypeptide |
| pancreatic amylase | breaks down starch in pancreas |
| trypsin, chymotrypsin, and carboxypeptidase | protein-digesting enzymes |
| pancreatic lipase | digests tryglycerides |
| ribonuclease and deoxyribonuclease | digests nucleic acids |
| enterokinase | activated form of trypsin |
| liver | weighs 1.4 kgs and is the second largest organ in the body |
| gallbladder | pear-shaped sac that hangs from the lower front margin of the liver |
| lobules | units of the liver |
| hepatocytes | specialized cells that make up lobules |
| sinosoids | highly permeable capillaries |
| emuslification | the breakdown of large lipid globules into a suspension of small lipid globules, and absorption of lipids following their digestion |
| bilirubin | principal bile pigment |
| absorptive cells | found in the small intestine, contain microvilli and digest and absorb nutrients in small intestinal chyme |
| s cells, CCK cells, and K cells | secrete hormones into the bloodstream such as secretin, cholecystokinin (CCK), and glucose-dependent insulinotropic peptide (GIP) |
| duodenal glands | secrete an alkaline mucus |
| circular folds | permanent ridges of the mucosa and submucosa that enhances absorption by increasing surface area |
| villi | fingerlike projections of the mucosa |
| lacteal | lymphatic capillary |
| microvilli | tiny projections of the plasma membrane |
| intestinal juice | secreted by the intestinal glands, contains mucus, alkaline |
| segmentations | localized contractions that slosh chyme back and forth |
| maltase | splits maltose into two molecules of glucose |
| sucrase | breaks sucrose into a molecule of glucose and a molecule of fructose |
| lactase | digests lactose into a molecule of glucose and a molecule of galactose |
| peptidases | enzymes produced by absorptive cells that line the villi |
| micelles | tiny droplets that include some bile salt molecules along with the long chain fatty acids, monoglycerides, cholesterol, and other dietary lipids |
| chylomicrons | large spherical particles that are coated with proteins |
| mass peristalsis | a strong peristaltic wave that begins in the middle of the colon and drives the colonic contents into the rectum |
| defecation reflex | result of mass peristalsis |
| cephalic phase | smell, sight, sound, or thought of food activates neural centers in the brain, leading to salivation |
| gastric phase | gastrin is released |
| intestinal phase | slows digestion |
Created by:
pontarelli
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