| 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. |
