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