Term
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Definition
-most nutrients we eat cannot be used in their existing form
–must be broken down into smaller components before our body can make use of them |
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Term
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Definition
–the physical breakdown of food into smaller particles
–cutting and grinding action of the teeth
–churning action of stomach and small intestines
–exposes more food surface to the action of digestive enzymes |
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Term
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Definition
–a series of hydrolysis reactions that breaks dietary macromolecules into their monomers (residues)
–carried out by digestive enzymes produced by salivary glands, stomach, pancreas and small intestine
•some nutrients are present in a usable form in ingested food
–absorbed without being digested
–vitamins, free amino acids, minerals, cholesterol, and water |
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Term
| results of chemical digestion |
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Definition
•polysaccharides into monosaccharides
•proteins into amino acids
•fats into monoglycerides and fatty acids
•nucleic acids into nucleotides |
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Term
| digestive tract (alimentary canal) |
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Definition
–30 foot long muscular tube extending from mouth to anus
–mouth, pharynx, esophagus, stomach, small intestine, and large intestine |
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Term
| gastrointestinal (GI) tract |
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Definition
| the stomach and intestines |
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Term
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Definition
| –teeth, tongue, salivary glands, liver, gallbladder, and pancreas |
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Term
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Definition
–lines the lumen and consists of:
–inner epithelium
–lamina propria
–muscularis mucosa
–mucosa-associated lymphatic tissue (MALT) |
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Term
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Definition
•simple columnar in most of digestive tract
•stratified squamous from mouth through esophagus, and in lower anal canal |
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Term
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Definition
| loose connective tissue layer |
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Term
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Definition
–thin layer of smooth muscle
-tenses mucosa creating grooves and ridges that enhance surface area and contact with food
-improves efficiency of digestion and nutrient absorption |
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Term
| mucosa-associated lymphatic tissue (MALT) |
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Definition
| the mucosa exhibits an abundance of lymphocytes and lymphatic nodules |
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Term
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Definition
–thicker layer of loose connective tissue
–contains blood vessels, lymphatic vessels, a nerve plexus, and in some places mucus secreting glands that dump lubricating mucus into the lumen
–MALT extends into the submucosa in some parts of the GI tract |
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Term
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Definition
| in some places, this layer thickens to form valves (sphincters) that regulate the passage of material through the tract |
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Term
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Definition
| responsible for the motility that propels food and residue through the tract |
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Term
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Definition
| composed of a thin layer of areolar tissue topped by simple squamous mesothelium |
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Term
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Definition
| a nervous network in the esophagus, stomach, and intestines that regulated digestive tract motility, secretion, and blood flow |
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Term
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Definition
| connective tissue sheets that loosely suspend the stomach and intestines from the abdominal wall |
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Term
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Definition
| a serous membrane that lines the wall of the abdominal cavity |
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Term
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Definition
| a ventral mesentery that extends from the lesser curvature of the stomach to the liver |
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Term
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Definition
| hangs from the greater curvature of the stomach |
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Term
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Definition
| extension of the mesentery that anchors the colon to the posterior abdominal wall |
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Term
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Definition
| when an organ is enclosed by mesentery on both sides |
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Term
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Definition
| when an organ lies against the posterior body wall and is covered by peritoneum on its anterior side only |
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Term
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Definition
| of the digestive tract are controlled by neural, hormonal, and paracrine mechanisms |
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Term
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Definition
–short (myenteric) reflexes
–long (vagovagal) reflexes |
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Term
| short (myenteric) reflexes |
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Definition
–stretch or chemical stimulation acts through myenteric plexus
•stimulates parastaltic contractions of swallowing |
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Term
| long (vagovagal) reflexes |
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Definition
| -parasympathetic stimulation of digestive motility and secretion |
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Term
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Definition
–chemical messengers secreted into bloodstream, and stimulate distant parts of the digestive tract
–gastrin and secretin |
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Term
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Definition
| –chemical messengers that diffuse through the tissue fluids to stimulate nearby target cells |
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Term
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Definition
| known as the oral, or buccal cavity, and is lined with stratified squamous epithelium |
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Term
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Definition
-the teeth
-masticate food into smaller pieces
–exposes more surface area for action of digestive enzymes speeding chemical digestion |
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Term
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Definition
| sticky residue on the teeth made up of bacteria and sugars |
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Term
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Definition
| calcified plaque; if in the gingival sulcus, it wedges the tooth and gum apart |
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Term
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Definition
| necessary if cavity reaches pulp |
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Term
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Definition
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Term
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Definition
| destruction of the supporting bone around the teeth which may result in tooth loss |
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Term
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Definition
| breaks food into smaller pieces to be swallowed and exposes more surface to the action of digestive enzymes |
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Term
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Definition
–begin starch and fat digestion
–cleanse teeth
–inhibit bacterial growth
–dissolves molecules so they can stimulate the taste buds |
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Term
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Definition
| enzyme that begins starch digestion in the mouth |
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Term
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Definition
| enzyme that is activated by stomach acid and digests fat after the food is swallowed |
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Term
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Definition
| binds and lubricates the mass of food and aids in swallowing |
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Term
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Definition
| enzyme that kills bacteria |
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Term
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Definition
| an antibody that inhibits bacterial growth |
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Term
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Definition
| Na+, K+, Cl-, phosphate and bicarbonate |
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Term
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Definition
| a muscular funnel that connects oral cavity to esophagus and allows entrance of air from nasal cavity to larynx |
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Term
| lower esophageal sphincter |
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Definition
–food pauses at this point because of this constriction
-prevents stomach contents from regurgitating into the esophagus
-protects esophageal mucosa from erosive effect of the stomach acid |
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Term
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Definition
| burning sensation produced by acid reflux into the esophagus |
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Term
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Definition
| a complex action involving over 22 muscles in the mouth, pharynx, and esophagus |
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Term
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Definition
| pair of nuclei in medulla oblongata that coordinates swallowing |
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Term
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Definition
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Term
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Definition
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Term
| The two phases of swallowing |
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Definition
-buccal phase
-pharyngoesophageal phase |
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Term
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Definition
–wave of muscular contraction that pushes the bolus ahead of it
–an entirely involuntary reflex |
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Term
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Definition
–a muscular sac in upper left abdominal cavity immediately inferior to the diaphragm
–primarily functions as a food storage organ
-mechanically breaks up food particles, liquefies the food, and begins chemical digestion of protein and fat
-most digestion occurs after the chyme passes on to the small intestine |
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Term
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Definition
| soupy or pasty mixture of semi-digested food in the stomach |
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Term
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Definition
–parasympathetic fibers from vagus
–sympathetic fibers from celiac ganglia |
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Term
| simple columnar epithelium |
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Definition
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Term
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Definition
–depressions in gastric mucosa
–lined with simple columnar epithelium
–two or three tubular glands open into the bottom of each gastric pit |
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Term
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Definition
–found mostly in the upper half of the gland
–secrete hydrochloric acid (HCl), intrinsic factor, and a hunger hormone called ghrelin
-produce HCl and contain carbonic anhydrase (CAH) |
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Term
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Definition
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Term
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Definition
–most numerous
–secrete gastric lipase and pepsinogen
–dominate lower half of gastric glands
–absent in pyloric and cardiac glands |
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Term
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Definition
–concentrated in lower end of gland
–secrete hormones and paracrine messengers that regulate digestion |
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Term
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Definition
| 2 to 3 liters per day produced by the gastric glands; mainly a mixture of water, hydrochloric acid, and pepsin; has a high concentration of hydrochloric acid |
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Term
| Functions of Hydrochloric Acid |
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Definition
•activates pepsin and lingual lipase
•breaks up connective tissues and plant cell walls
–helps liquefy food to form chyme
•converts ingested ferric ions (Fe3+) to ferrous ions (Fe2+) |
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Term
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Definition
| digests dietary proteins into shorter peptide chains |
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Term
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Definition
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Term
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Definition
•gastric and pyloric glands have various kinds of enteroendocrine cells that produce as many as 20 chemical messengers
–some are hormones enter blood and stimulate distant cells
–others are paracrine secretions that stimulate neighboring cells
–several are peptides produced in both the digestive tract and the central nervous system –gut-brain peptides |
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Term
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Definition
-soon stomach shows a rhythm of peristaltic contractions controlled by pacemaker cells in longitudinal layer of muscularis externa
–as a parastaltic wave passes down the antrum, it squirts about 3 milliliters of chyme into the duodenum at a time
–allowing only a small amount into the duodenum enables the duodenum to:
-neutralize the stomach acid
-digest nutrients little by little |
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Term
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Definition
| the forceful ejection of stomach and intestinal contents (chyme) from the mouth |
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Term
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Definition
| in the medulla oblongata integrates multiple muscle actions |
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Term
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Definition
| thoracic expansion and abdominal contraction creates a pressure difference that dilates the esophagus |
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Term
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Definition
| thick, highly alkaline mucus resists action of acid and enzymes |
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Term
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Definition
| between epithelial cells prevent gastric juice from seeping between them and digesting the connective tissue of the lamina propria and beyond |
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Term
| epithelial cell replacement |
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Definition
-stomach epithelial cells live only 3 to 6 days
-sloughed off into the chyme and digested with the food
-replaced rapidly by cell division in the gastric pits |
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Term
| Protection of the Stomach |
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Definition
| breakdown of these protective measures can result in inflammation and peptic ulcer |
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Term
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Definition
| inflammation of the stomach which can lead to a peptic ulcers as pepsin and hydrochloric acid erode the stomach wall |
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Term
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Definition
| most ulcers are caused by this acid-resistant bacteria and can be treated with antibiotics and Pepto-Bismol |
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Term
| the three phases that gastric activity is divided into |
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Definition
–cephalic phase
–gastric phase
–intestinal phase |
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Term
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Definition
-stomach being controlled by brain
–stomach responds to site, smell, taste, or thought of food
–sensory and mental inputs converge on the hypothalamus
•relays signals to medulla oblongata
–vagus nerve fibers from medulla oblongata stimulate the enteric nervous system of stomach
•in turn, stimulates gastric secretion |
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Term
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Definition
–stomach controlling itself
–period in which swallowed food and semi-digested protein activates gastric activity |
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Term
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Definition
–stomach being controlled by small intestine
–stage in which the duodenum responds to arriving chyme and moderates gastric activity through hormones and nervous reflexes
–duodenum initially enhances gastric secretion, but soon inhibits it |
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Term
| Liver, Gallbladder, and Pancreas |
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Definition
| secretions are so important to the digestive process of the small intestine |
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Term
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Definition
–reddish brown gland located immediately inferior to the diaphragm
–function is to secrete bile which contributes to digestion |
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Term
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Definition
| cuboidal cells surrounding central vein in radiating sheets or plates |
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Term
| hepatic macrophages (Kupffer cells) |
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Definition
| phagocytic cells in the sinusoids that remove bacteria and debris from the blood |
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Term
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Definition
•after a meal, the hepatocytes absorb from the blood
–glucose, amino acids, iron, vitamins, and other nutrients for metabolism or storage
•removes and degrades
–hormones, toxins, bile pigments, and drugs
•secretes into the blood:
–albumin, lipoproteins, clotting factors, angiotensinogen, and other products
•between meals, hepatocytes breaks down stored glycogen and releases glucose into the blood |
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Term
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Definition
–a pear-shaped sac on underside of liver
–serves to store and concentrate bile by a factor of 20 by absorbing water and electrolytes |
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Term
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Definition
–yellow-green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids
–20% of the bile acids are excreted in the feces
-this is the body's only way of eliminating excess cholesterol
-liver synthesizes new bile acids from cholesterol to replace those lost in feces |
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Term
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Definition
| principal pigment derived from the decomposition of hemoglobin |
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Term
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Definition
| use of ultrasonic vibration topulverize stones without surgery |
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Term
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Definition
–spongy retroperitoneal gland posterior to the greater curvature of the stomach
–both an endocrine and exocrine gland |
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Term
| endocrine portion of the pancreas |
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Definition
| pancreatic islets that secrete insulin and glucagon |
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Term
| exocrine portion of the pancreas |
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Definition
| 99% of pancreas that secretes 1200 to 1500 milliliters of pancreatic juice per day |
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Term
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Definition
–alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes
•ducts secrete bicarbonate
–bicarbonate buffers HCl arriving from the stomach |
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Term
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Definition
•gradual movement of contents towards colon
•ileocecal valve usually closed
–food in stomach triggers gastroileal reflex that enhances segmentation in the ileum and relaxes the valve
–as cecum fills with residue, pressure pinches the valve shut
•prevents reflux of cecal contents into the ileum |
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