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Digestive tract
digestive tract terms and functions
| Question | Answer |
|---|---|
| Primary function of the digestive system | Transfer nutrients, water, and electrolytes from ingested food into body’s internal environment |
| Four functions of the digestive system | – Motility – Secretion – Digestion – Absorption |
| Two types of digestive motility | Propulsive movements Mixing movements |
| Propulsive movements | Push contents forward through the digestive tract |
| Mixing movements [2] | Serve two functions -Mixing food with digestive juices promotes digestion of foods -Facilitates absorption by exposing all parts of intestinal contents to absorbing surfaces of digestive tract |
| Secretion [3] | – Consist of water, electrolytes, mucus, enzymes, antibodies – Secretions are released into digestive tract lumen – Some reabsorbed in one form or another back into blood after their participation in digestion |
| Digestion | Biochemical breakdown of structurally complex foodstuffs into smaller, absorbable units |
| How is digestion accomplished? | Accomplished by enzymatic hydrolysis |
| Complex foodstuffs and their absorbable units: Carbohydrates >> | Carbohydrates → monosaccharides |
| Complex foodstuffs and their absorbable units: Fats >> | Fats → glycerol and fatty acids |
| Complex foodstuffs and their absorbable units: Proteins >> | Proteins → di and tripeptides and amino acids |
| Absorption [Be as specific as you can] | Small units resulting from digestion, along with water, vitamins, and electrolytes are transferred from digestive tract lumen into blood or lymph |
| Four major tissue layers throughout the length of the esophagus to the anus | – Mucosa – Submucosa – Muscularis externa – Serosa |
| Innermost layer | Mucosa |
| Outermost layer | Serosa |
| Many Sloths Move Slowly | – Mucosa – Submucosa – Muscularis externa – Serosa |
| Help procure, guide, and contain food in the mouth | Lips |
| Well-developed tactile sensation | Lips |
| Forms roof of oral cavity (separates mouth from nasal passages) | Palate |
| Uvula (seals off nasal passages during swallowing) | Palate |
| Forms floor of oral cavity, Composed of skeletal muscle | Tongue |
| Movements aid in chewing and swallowing, taste buds | Tongue |
| Responsible for mastication | Teeth |
| First step in digestive process | Teeth |
| Grind and break food into smaller pieces to make swallowing easier and increase food surface area on which salivary enzymes can act | Chewwing |
| Composition of saliva __ __ . __ % H2O __. __% electrolytes and protein (amylase, mucus, lysozyme) | 99.5% ; 0.5% |
| Saliva produced largely by ____ ____ ____ of salivary glands | Three major pairs |
| Facilitates swallowing by moistening food | Saliva functions |
| Begins digestion of carbohydrates | Salivary amylase begins digestion of carbohydrates |
| Antibacterial action of saliva | – Lysozyme destroys bacteria – Saliva rinses away material that could serve as food source for bacteria |
| Also known as the throat | Pharynx |
| Muscular tube from pharynx to stomach | Esophagus |
| Upper 1/3—_____ muscle Lower 2/3—_____ muscle | Esophagus Skeletal Smooth |
| Common passageway for air and food | Pharynx |
| Upper esophageal sphincter | Skeletal muscle between pharynx and esophagus |
| Lower esophageal sphincter | Smooth muscle between esophagus and stomach |
| J-shaped sac-like chamber lying between esophagus and small intestine | Stomach |
| Stomach divided into three sections | Fundus Body Antrum |
| Fat Baby Ass | Fundus Body Antrum |
| Secretes hydrochloric acid (HCl) and enzymes that begin protein digestion | Stomach |
| Mixing movements convert pulverized food to chyme | Stomach |
| Store ingested food until it can be emptied into small intestine | Stomach |
| Serves as barrier between stomach and upper part of small intestine | Pyloric sphincter |
| Secretory products of the stomach | - Pepsinogen secreted by chief cells - Hydrogen ions secreted by parietal cells - Intrinsic factor secreted by parietal cells - Gastrin secreted from G cells (hormone) - Mucus secreted from neck cells |
| Precursor for pepsin, enzyme that digests proteins | Pepsinogen |
| Maintain acidic environment of stomach | Hydrogen ions secreted by parietal cells |
| Necessary for absorption of vitamin B12 | Intrinsic factor secreted by parietal cells |
| Coiled hollow tube 8-10 ft long | Small intestine |
| Site where most digestion and absorption take place | Small intestine |
| Three segments of small intestine | – Duodenum – Jejunum – Ileum |
| Dont Jerk It | – Duodenum – Jejunum – Ileum |
| Juice secreted by _____ _____ does not contain any digestive enzymes | Small intestine |
| Describe the juice secreted by the small intestine | Aqueous salt and mucus solution |
| ______ ______ and ______ empty into duodenum | Pancreatic enzymes ; bicarbonate |
| ____________ – trypsinogen → trypsin | Enterokinase |
| Disaccharidases – __________ → monosaccharides | Disaccharides |
| Aminopeptidases – __________ → amino acids | Peptides |
| _______ _______ releases bile into duodenum | Gall bladder |
| Fat is digested entirely within ______ ______ lumen by pancreatic lipase | Small intestine |
| _______-_______ enzymes complete digestion of carbohydrates and protein | Brush-border |
| Absorbs almost everything presented to it | Small intestine |
| What is a "brush-border" and what is the purpose of it | Brush border (microvilli) arise from luminal surface of epithelial cells. It is important to increase the surface area and therefore increase absorption. |
| Adaptations that increase small intestine’s surface area | Folds, villi, and microvilli |
| Contain blood vessels and lacteal for absorption of nutrients | Villi |
| Form brush border | Microvilli |
| Only _________ are absorbed | Monosaccharides |
| Typical diet: _____-_____ grams carbohydrates | 250–800 grams |
| Most consumed as disaccharides or polysaccharides | – Sucrose – Lactose – Maltose – Starch – Glycogen – Cellulose (fiber, cannot be digested) |
| Digestion of Starch: [2 enzymes] | – Salivary amylase – Pancreatic amylase |
| End product of starch. | End product – Disaccharides (maltose) – Limit dextrins |
| Carbohydrate Digestion: Enzymes: ________ – limit dextrins > glucose | Dextrinase |
| Carbohydrate Digestion: Enzymes: _______ – polysaccharides > glucose | Glucoamylase |
| Carbohydrate Digestion: Enzymes: _______ – sucrose > fructose + glucose | Sucrase |
| Carbohydrate Digestion: Enzymes: _______ – lactose > galactose + glucose | Lactase |
| Carbohydrate Digestion: Enzymes: ______ – maltose > 2 glucose | Maltase |
| Location of enzymes— | Brush border of small intestine |
| Transport from lumen to blood | Absorption |
| Glucose and galactose absorbed by | – Secondary active transport across apical membrane – Facilitated diffusion across basolateral membrane |
| Fructose absorbed by | Facilitated diffusion across both membranes |
| Typical diet: ___ grams/day protein – Only require __-__ grams | 125 grams ; 40–50 grams |
| Proteins digested by proteases into | – Amino acids – Dipeptides – Tripeptides |
| Protein digestion begins in the | Stomach |
| Protein Digestion Enzyme released by the stomach ; by which cells ; is converted into | Pepsinogen ; Chief cells ; Pepsin |
| What is pepsinogen? | Inactive form of pepsin |
| What activates pepsinogen? | Acid |
| Pancreatic proteases | – Trypsin – Chymotrypsin – Carboxypeptidase |
| Brush border proteases | – Aminopeptidase – Enterokinase |
| Amino acids – Cross apical membrane by sodium-linked ______ ______ transport or ______ ______. – Cross basolateral membrane by ______ ______ | Secondary active ; facilitated diffusion ; facilitated diffusion |
| Di and Tripeptides – Cross apical membrane by______ ______ – Broken down inside cell to ______ ______ – Amino acids cross basolateral membrane by _____ _____ | Active transport ; amino acids ; facilitated diffusion |
| What is the difference between exogenous and endogenous proteins? | Exogenous is dietary protein; endogenous proteins are digestive enzymes, sloughed epithelial cells, and leaked plasma proteins. |
| Lipid Digestion Typical diet: __-___ grams lipids – __% triglycerides | 25–160 grams ; 90% |
| Lipids face special problem in digestion and absorption... which is... | – Not water soluble – Do not mix with stomach, intestinal contents – Form fat droplets |
| Lipid Digestion: Enzymes of digestion = _______ | Lipases |
| Lipase is secreted from the ______ and is the enzyme for ___ breakdown. | Pancreas ; fat/lipid |
| Lipases can only act on molecules near edge of ___ _____ | Fat droplet |
| ____ _____ increase surface area of droplets by breaking large droplet into several small droplets = a process called.. | Bile salts ; emulsification |
| Bile Salts: Synthesized in _____ from ________. | Liver, Cholesterol |
| Bile Salts: Secreted in _____ to _______ | Bile ; duodenum |
| Bile Salts: ________ molecule, that works to ______ fat | Amphipathic, emulsify |
| Triglycerides > Monoglyceride + _______ Digestion by Lipases - Some fatty acids and monoglycerides absorbed - Others form micelles | 2 Fatty acids ; micelles |
| Free form can be absorbed by Monoglycerides and Fatty Acids______ ______ across epithelium | Simple diffusion |
| Monoglycerides and Fatty Acids Once Inside epithelial cell (through ____ ____) enters the _____ _____ and reform triglycerides and other lipids. Lipids then enter ____ ____ to be packaged into chylomicrons | Simple diffusion ; Smooth ER ; Golgi apparatus |
| Lipase is secreted by the | Pancreas |
| Chylomicrons secreted by _____ into interstitial fluid Chylomicrons enter______ ______ via lacteal | Exocytosis ; lymphatic system |
| Pancreas is a mixture of ________ and ________ tissue | Exocrine ; endocrine |
| Elongated gland located behind and below the stomach | Pancreas |
| Endocrine function of the pancreas | Secrete insulin and glucagon |
| What part of the pancreas secretes insulin and glucagon | Islets of Langerhans |
| Exocrine function of the pancreas | Secretes pancreatic juice consisting of - Pancreatic enzymes actively secreted by acinar cells that form the acini - Aqueous alkaline solution actively secreted by duct cells that line pancreatic ducts |
| Pancreatic Enzymes: Proteolytic enzymes [ 3 ] | Trypsinogen Chymotrypsinogen Procarboxypeptidase |
| Trypsinogen converted to ; for... | Converted to active form trypsin ; Digestion of protein |
| Chymotrypsinogen is converted to active form ; for... | Chymotrypsin ; Digestion of protein |
| Procarboxypeptidase is converted to active form ; for... | Carboxypeptidase ; Digestion of protein |
| Pancreatic Amylase vs Pancreatic Lipase | Converts polysaccharides into the disaccharide amylase Main enzyme that can digests fat |
| Largest and most important metabolic organ in the body | Liver |
| Body’s major biochemical factory | Liver |
| Liver receives blood from two sources | – Arterial blood via hepatic artery – Venous blood from via hepatic portal vein |
| Importance to digestive system – secretion of bile salts | Liver |
| Functions of the liver not related to digestion [7] | – Metabolic processing – Detoxifying – Synthesizes plasma proteins – Stores glycogen, fats, iron, copper, and many vitamins – Activates vitamin D – Removes bacteria and worn-out red blood cells – Excretes cholesterol and bilirubin |
| Bile: Actively secreted by _____ and actively diverted to ________ between meals | Liver ; Gallbladder |
| Bile consists of [4] | Bile salts Cholesterol Lecithin Bilirubin |
| Primarily a drying and storage organ | Large intestine |
| Large intestine consists of what four parts | – Colon – Cecum – Appendix – Rectum |
| Colon: Extracts more _____ and _____ from contents | Water ; salts |
| Colonized by beneficial bacteria | Large intestine |
| ____-_____ different bacterial species present in large intestine | 500-1000 |
| Functions of bacteria in large intestine [6] | - Enhance intestinal immunity by out competing pathogenic bacteria -Promote colonic motility -Help maintain mucosal integrity -Ferment fiber -Produce vitamin K -Decrease colonic pH allowing calcium, magnesium and zinc absorption |
| The chyme entering the intestine from the stomach is: | very basic and quickly buffered by digestive enzymes excreted from the pancreas. |
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