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Digestive tract

digestive tract terms and functions

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.
Created by: 811969848858069



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