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67 Cards in this Set
- Front
- Back
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Cells
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smallest fxnl unit, requires energy (ATP) and nutrients
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Organization of human body
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Epithelial tissue - lines body surfaces, secretes substances, absorbs nutrients, excretes waste
Connective tissue - supports and protects body, stores fat, produces blood cells Muscle tissue - movement Nervous tissue - communication |
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Digestive system functions
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digestion, absorption, transport, storage, excretion
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Organ Systems
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cardiovascular, lymphatic, nervous, endocrine, immune, digestive, urinary, integumentary, skeletal, muscular, respiratory, reprodutive
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GI tract
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mouth, esophagus, stomach, SI, LI, rectum, anus
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Accessory organs of digestion
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salivary glands, liver, GB, pancreas
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GI tract anatomy
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AKA alimentary canal, 15 feet from mouth to anus, 4 layers-mucosa submucosa, muscle, serosa (inner to outer)
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Mouth and salivary glands
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chew food, perceive taste, moisten food with saliva, lubricate food with mucus, release starch-digesting (amylase) enzyme, initiate swallowing reflex
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Esophagus
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lubricate with mucus, move foor to stomach by peristalic waves
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Stomach
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store, mix, dissove, and continue digestion of food, dissove food particles with secretions kill microorganisms with acid, release protein-digesting (pepsin) enzyme, lubricate and protect stomach surface with mucus, regulate emptying of dissolved food into SI, produce intrinsic factor for vitamin B12 absorption
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Liver
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produce bile to aid fat digestion and absorption
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GB
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store, concentrate, and later release bile into SI
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Pancreas
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secrete sodium bicarbonate and enzymes for digesting carbs, fat and protein
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SI
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mix and propel contents, lubricate with mucus, digest and absorb most substances using enzymes made by pancreas and SI
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LI
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mix and propel contents, absorb sodium, potassium, and water, house bacteria, lubricate with mucus, synthesize some vitamins and short-chain fatty acids, form feces
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Rectum
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hold feces and expel via the anus, which is the opening to the outside of the body
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Sphincters of the GI tract
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lower esophageal (prevent reflux of stomach into esophagus), pyloric (control flow of stomach into SI), sphincter of oddi (control flow of bile from CBD into SI), ileocecal (prevent contents of LI from reentering SI), anal (prevent defecation until desired)
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GI tract motility
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Food is mixed with degestive sectetions and propelled down GI tract by peristalsis
Peristalsis starts in esophagus and goes through entire GI tract Thickest and strongest muscle of GI tract are in stomach Most frequent peristalsis takes place in SI (contractions every 4-5 seconds) SI also has segmental contractions (segmentation), which move the intestinal contents back and forth, causing contents to break apart and mix with digestive juices |
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Secretions
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saliva, mucus, hydrochloric acid, digestive enzymes, hormones, bicarbonate, bile, water
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Saliva
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Mouth
Contributes to starch digestion, lubrication, swallowing |
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Mucus
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Mouth, stomach, SI, LI
Protects GI tract cells, lubricates digesting food |
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Enzymes
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Mouth, stomach, SI, pancreas
Promotes digestion of carbs, fats, and protein into forms small enough for absorption |
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Acid (HCl)
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Stomach
Promotes digestion of protein, destroys microorganisms, increases solubility of minerals |
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Bile
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Liver (stored in GB)
Aids in fat digestion (emulsifies fat) |
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Bicarbonate
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Pancreas, SI
Neutralizes stomach acid when it reaches SI |
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Hormones
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Stomach, SI
Regulates digestion and absorption |
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Cooking and food preparation
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pre-digestion
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Mouth
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Chewing
Saliva - enzymes to help break down simple sugars, mucus to lube the food for easier swallowing, lysozyme to kill bacteria Tongue - taste receptors, flavor is enhanced with the olfactory cells, enzymes to help break down fatty acids Epiglottis |
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Saliva info
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Daily volume - 800-1500 ml
>95% water |
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Saliva - a-amylase
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Digestive enzyme
Partial digestion of starch - limit dextrins Inactivate by low pH in stomach (6-7 favorable range) |
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Saliva - mucus
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Water
Electrolytes (K, HCO) Glycoproteins (mostly polysaccharides with some protein, mucin) Lubricant - facilitates swallowing, coat wall of gut (prevents food from sticking to it), resistant to breakdown by digestive enzymes, small buffering capacity (prot and HCO3), facilitates adherence of fecal material and removal of feces |
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Saliva - lysozyme
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Digestive enzyme
Breaks cell wall of bacteria (B1-4 glycosidase activity) and allows entry of thiocyanate (bactericidal) |
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Saliva - R-protein
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Stabilizes free Vit B12
Essential for Vit B12 absorption |
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Stomach info
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Beg (esophageal sphincter and end (pyloric sphincter)
Capacity - 4 cups (1L) Parietal cells secrete hydrochloric acid, aides protein digestion, solubilizes minerals for absorption Chief cells secrete enzymes Holds foor for 2-4 hours Results in formation of chyme Mucus layer prevents autodigestion Secretion of the intrinsic factor |
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Gastric secretions
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Daily volume- 1500 ml (6 cups)
Water Hydrochloric Acid - secreted by parietal cells, kills some food bacteria, initiates activation of pepsinogen, denatures and facilitates digestion of dietary protein, partially digests dietary protein, solubilizes and keeps minerals reduced to facilitate absorption, releases food-bound Vit B12 and allows binding to R-protein pH 1-2 ideal for pepsinogen activation and partial digestion of dietary protein |
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Gastric secretions - mucus
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Secreted by goblet cells
See saliva for details |
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Gastric secretions - pepsinogen
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Secreted by chief cells and activated to pepsin
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Gastric secretions - intrinsic factor (IF)
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Secreted by parietal cells
A glycoprotein that binds to Vit B12 released from R-protein by trypsin in the SI and binds to carriers in the ileum allowing Vit B12 absorption |
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Gastric secretions - hormones (into blood)
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Histamine - secreted by enterochromaffin-like (ECL) cells, stimulates (with Acetylcholine) acid secretion by parietal cells and perhaps decreases appetite and food intake
Gastrin - secreted by gastrin (G) cells, stimulates pepsinogen and acid secretion Ghrelin - acts as a short-term appetite stimulant |
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SI
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3 segments - duodenum (10"), jejunum (4'), ileum (5')
Narrow diameter Food remains for 3-10 hours 95% of digestion takes place in SI (mostly duodenum and upper jejunum) |
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Pancreatic secretions
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Daily volume - 1000 ml (4 cups)
Water Sodium bicarbonate - formed from metabolic CO2, Neutralizes stomach contents and brings pH to 7-8 A-Amylase - partial digestion of starch into dextrins Secreted in form of zymogens - pro-lipase and pro-proteases released in the SI and activated by trypsin, activation of trypsin is initiated by enteropeptidase, an active intestinal protease Pancreatic secretion is regulated by acetylcholine (neuro-transmitter) and secretin (intestinal hormone |
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Pancreatic secretions - hormones
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Insulin - decreases blood glucose and regulates metabolism of carbs and lipids, released by B cells mostly because of high blood glucose
Glucagon - stimulates release of glucose from liver and regulates metabolism of carbs and lipids, released by A cells because of low blood glucose |
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SI secretions
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Daily volume - 1800 ml (7 cups)
Water and mucus Ions (Na, K, Ca, Cl. HCO3) Enteropeptidase - starts the activation of pancreatic trypsinogen Active trypsin completes its own activation and activates the other zymogens (Pro-lipases and pro-proteases) |
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SI secretions
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Sucrase (digests sucrose)
Lactase Maltase (maltose from starch) a 1-4 (2 GLC) Isomaltase (isomaltose from starch) a 1-6 ( 2 GLC) Glucoamylase (maltotriose from starch) (3 GLC) |
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SI scretions - hormones
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Peptide PYY - secreted by SI and LI into blood, short-term appetite supressor
Gastic inhibitory peptide - Secreted by SI into blood, inhibits stomach motility, stimulates insulin secretion Secretin - secreted by duodenum and jejunum into blood, stimulates secretion of pancreatic bicarbonate Sholecystokinin - secreted by duodenum and jejunum into blood, stimulates pancreatic secretion (mostly zymoens), inhibits stomach motility |
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Bile
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Daily volume - 1000 ml (4 cups)
Water - 95 % Emulsifiers - bile salts, cholesterol, lecithin, fatty aids Billirubin - for elimination Ions - Na, K, Ca, Cl, HCO3 |
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Absorption in SI
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Virtually all nutrients are absorbed in SI
Absorbs 95% of food energy in prot, carbs, fat, and alcohol Type of absorption depends on nature of dietary nutrients Transport of absorbed dietary nurients depends on their solubilities |
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Primary nutrients absorbed
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Stomach - alcohol (20% total), water (minor amount)
SI - Ca, magnesium, Fe, and other minerals, GLC, a.a, vit,water (70-90% of total), alcohol (80% of total), bile acids LI - Na, K, some faty acids, gases, water (10-30% of total) |
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Specific absorptions
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Fats - a MAGs by passive transport
Proteins - as free a.a. by secondary active transport usng a sodium gradient Carbs - GLC and galactose by secondary active transport using a sodium gradient (SGT), fructose by passive transport (GLUT5), and mannose nobody knows |
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Absorptive cells
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Intestinal mucosa consists of absorptive cells, mucosal cells, and endocrine cells
Degradation of cells at the tips of the villi by digestive enzymes, sloughed off Newly formaed cells constantly migrate to replace dying ones (< 6 days) High turnover causes the cells to deteriorate during nutrient deficiency Entire supply of enterocytes replaced every 2-5 days |
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Cardiovascular system
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Includes the heart, blood vessels, and blood
Water-soluble nutrients (minerals, a.a., monosaccharides, short and medium chain fatty acids, and water-soluble vit) are transported by the CV system These are absorbed directly into the bloodstream in the capillary beds inside the villi Blood flows from the capillary beds and collects in the large portal vein which leads directly to the liver |
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Lymphatic system
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Contains lymph, which flows throughout the body in lymphatic vessels
Provides an alternative route into the blood for large and fat-soluble molecules that cannot be absorbed by the capillary beds Fat-soluble nutrients (most fats and fat-soluble vit) and large particles are transported in lymph Special lymph vessels (lacteals) in the villi carry nutrients to larger lymphatic vessels that connect to the thoracic duct (TD) TD extends from abdomen to neck and connects to the bloodstream at subclavian vein Once in blood, nutrients originally a bsorbed by the lymph system are transported to body tissues in the CV system |
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Blood circulation
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External respiration - lungs, capillaries - CO2 out and O2 in
Internal respiration - peripheral tissues, capillaries - O2out and CO2 in |
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LI
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5' long and 2 1/2" in diameter
5% of prot, carbs, and fat escapes absorption in SI 3 parts - colon, rectum, anus Colon - cecum, ascending, transverse, descending, and sigmoid colons 3 fxns - houses bacteria flora that keeps the GI tract healthy, absorbs water, electrolytes and gases, forms and expels feces |
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Bacterial Flora
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LI home to 400 species of bacteria, 100 trillion microbial cells (10x number of cells in body)
Most bacteria beneficial, some not Ileocecal sphincter prevents migration into SI Beneficial bacteria keep growth of pathogenic bacteria under control Synthesizes vit K and biotin, aids in lctose digestion and ferments soluble fiber, generating short-chain FA that can be used as energy source in the colon |
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Probiotics and prebiotics
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One idea for achieving a healthy balance of intestinal bacteria
Pro - live microorganism that provide health benefits when consumed in sufficient amts Pre - non-digestive carbs that promote growth of beneficial bacteria in LI |
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Probiotics
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In fermented foods - yogurt and miso (fermented soybean paste) and sold in capsules and powder
Lactobacilli or bibidobacteria Colonize in the LI and provide health benefits May help and prevent diarrhea, prevent food allergies and colon cancer, and treat IBS and inflammatory bowel disease (not conclusive) Can help prevent and treat diarrhea in children (evidence) |
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Prebiotics
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One example is inullin - a carb made of several units of fructose - found in chicory, wheat, onions, garlic, asparagus, and bananas
Inullin and fructans are added to some processed foods to add texture, bulk and potential health benefits Resistant starch (form of fiber) - found in whole grains and some fruits - escapes digestion in the SI but is fermented in the LI producing short chain FA and other organic acids - not conclusive |
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Water and electrolyte absorption
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GI tract receives about 10 L of water a day (3 from food and 7 from body secretions)
SI absorbs about 90% of the water and the LI completes job About 1% (1/2 cup or 100ml) of water in GI tract remains in excreted feces LI also absorbs electrolytes, especially Na and K Electrolyte absorption occurs mostly in the first half of the LI |
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Defecation of feces
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Takes 12-24 hours for the residue of a meal to travel through the LI
Feces in rectum is stimulation for defecation (expulsion of feces) Feces normally about 75% water and 25% solids (depending on diet, health, etc) Solids are primarily indigestible plant fibers, tough connective tissues from animal foods, and cell residue and bacteria from the LI |
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Storage capabilities of the body
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Fat stored in adipose tissue
Short term storage of carbs in muscle (2%wt), liver (10%wt) and blood Liver stores vit and minerals - excess of most vit and minerals is excreted via urine - caution with vit A Calcium stored in bone Prot obtained from muscle tissue |
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Digestive problems
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Heartburn and GERD, ulcers, gallstones, food intolerances, intestinal gas, constipation, diarrhea, IBS, hemorrhoids
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Preventing ulcers from occurring or recurring
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Stop smoking, avoid large doses of aspirin, ibuprofen, and other NSAIDs or take with a med that reduces gastric damage, limit intake of coffee, tea, alcohol, limit consumption of pepper, chili powder, and other strong spices, eat nutritious meals on a regular schedule, include enough fiber, chew food well, lose weight
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Preventing heartburn from occurring or recurring
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follow ulcer prevention recommendations, wait about 2 hrs after a meal before lying down, don't overeat, small meals that are low in fat, elevate head of be 6"
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Factors associated with gallstone formation
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High calorie, low fiber diets
Prolonged fasting Obesity (excess abdominal fat) Rapid weight loss Type 2 diabetes High blood lipids Sedentary lifestyle Some meds (estrogen replacement, birth control) Female Pregnancy Increasing age Family history Ethnicity (Native or Mexican Americans) |
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Carbs and gas formation
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Raffinose and Stachyose - sugars found in beans and veg (cabbage, brusselsprouts, brocoli) that are poorly absorbed
Lactose - milk products Fructose - fruit, onions, artichoke, and wheat Sorbitol - sugar alcohol that is poorly absorbed - frits (apples, pears, prunes) and used sweeten some sugar-free products Starches - potatoes, corn, noodles, and wheat not fully digested Fiber - soluble fiber found in beans, oat bran and fruits |
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Fiber effects
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Eating foods with plenty of fiber (whole grain bread and cereals, beans, fruits, veg) and driking plety of fluids helps i te prevention and treatment of mild cases of heartburn, GERD, ulcers, consipation, IBS, and hemorrhoids
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