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Mammalogy (Spring 2015 Althoff) LEC 06A Mammalian Digestive System BASICS Maintenance Systems • __________________—various organs along the digestive tract (from teeth to large intestine) A) receives food B) digests & absorbs nutrients C) excretes undigestible parts (feces) • __________________—lungs A) takes in O2 from “outside” environment B) takes out CO2 from “inside” environment • __________________—kidneys, bladder, & tubes A) rids blood of metabolic wastes B) helps regulate fluid level & chemical content of blood Maintenance Control Systems DIGESTIVE RESPIRATORY URINARY Food - IN _____________ OUT CO2 OUT, O2 IN ______________OUT FUNCTIONS of the Digestive System Breakdown the food that we eat into __________________ ________ those molecules into the body Eliminate __________________ waste Breakdown the food into small molecules _________________ = process of breaking down food into simple molecules Two types: ____________ ____________ = chewing, physical breakdown = digestive enzymes (catabolism) Foodstuffs broken down into simple molecules: Proteins amino acids Carbohydrates monosaccharides Lipids glycerol and fatty acids ABSORB the simple molecules _______ doesn’t really “enter” the body until it is absorbed Must pass through: _________________ blood stream Unfortunately, we do not ___________ the process of absorption….animals designed to maximize extraction of nutrients from “resources” ingested. This leads to the issue of gaining weight if we overeat. ELIMINATE non-digestible waste Any compound of food (emphasis “food”) we _______________ will be eliminated. Ex. for humans: Cellulose (found in cell walls of plants) _______ in normal, functioning human being, contains no undigestible material…so very little waste. Organs of the DIGESTIVE System • • • • • • • Mouth Pharynx-throat Esophagus Stomach Small Intestine Large Intestine Rectum/Anus • • • • Salivary glands Pancreas Liver Gall bladder Organs of the DIGESTIVE System • • • • • • • Mouth Pharynx-throat Esophagus Stomach Small Intestine Large Intestine Rectum/Anus • • • ___________organs • Salivary glands Pancreas Liver Gall bladder As each organ and/or “stop” is examined, think…… 1) FUNCTION--what is it 2) DIGESTION—does it occur here? (i.e., mechanical or chemical) 3) ABSORPTION—does it occur here? (are amino acids, fatty acids & glycerol, and simple sugars truly “entering” the body?) Mouth • Oral cavity that receives food • Tastebuds so we can taste food • Salivary glands secrete saliva - moistens food to make easier to swallow - starts digestion of starches (pH ~7.0), some sugars • ____ ABSORPTION, small amt. of digestion • Some bacteria destroyed • Mastication of food— __________________ for digestive juices to work on MASTICATION: DIFFERENT TEETH FOR DIFFERENT DIETS HERBIVORES: flat premolars & molars HUMANS: variety CARNIVORES: killing (canines), shearing (premolars & molars MASTICATION: “chewing” differences A 1 Mandibular ________ and ________ groups Position of the condyle (arrow) relative to the plane of teeth differs between carnivores (A) and herbivores (B). Thus, the ___________ muscles (1) are primary group of chewing muscles for carnivores, whereas the ___________ (2) are the primary group for herbivores B 2 Fig. 4-193 p64 FDVMK Pharynx • Swallowing, no voluntary control • Food now called “BOLUS” ___ absorption, ___ digestion Esophagus • Tube from pharynx to stomach • Food moves by PERISTALIS …smooth mucsle contractions • Passes lower esophageal sphincter into stomach: a) prevents backup b) acidic gastric juices backup…heartburn results because lining irritated Stomach • J-Shaped organ • Functions: 1) store meal for 2 hours 2) small amt. of protein digestion 3) _____ bacteria in bolus “if it can get to it” • pH of 2.0 with HCl added Stomach…continued • Muscus secreted protects stomach lining from pH of 2.0 – ulcers result if insufficient • HCl breakdowns down connective tissue • Pepsin enzyme starts protein digestion • ____________, _____ ________ (alcohol & some vitamins • Bolus chyme (vomit) as it leaves stomach Ruminants: 4 chambered stomach Small Intestine (SI) • 9-10 ft. in adults • Functions: __________ & __________ “big time” • Walls of SI lined with _________ – tremendous amt. of surface area Microvilli : area of absorption, link to transport systems (cardiovascular & lymphatic capillaries ) Individual cells have ___________ Small Intestine (SI) • _____ chemical digestion: -pancreatic juices breaks down proteins & carbs. Buffers chyme to pH 7.0 (from 2.0) -bile from liver and gall bladder. Emulsify fats Lipase—break down triglycerides Small Intestine (SI) • ______ absorption: -amino acids -simple sugars -fatty acids….. all to the liver via the bloodstream Different diets, different SI designs HIGH in protein (meat) CARNIVORES LOW in protein (vegetation) HERBIVORES Large Intestine (LI) • 4.5-5 ft in adults • After first few inches, considered colon • Functions: -_____ digestion (some vitamins--in cecum) -_____ absorption of water Large Intestine (LI)…con’t • Diarrhea—LI doesn’t get enough time to do its job…that is to remove water from wastes. A good “thing” if overload of bacteria present • Constipation—LI tract not moving things through at regular pace, more water removed than normal, feces hard • POLYPS– found here, in epithelial tissue…. caused by cancer Auxillary Organs: __ DIGESTION, __ ABSORPTION • LIVER— function here is producer of bile. Contains components of dead red blood cells, giving feces color. Bile emulsifies fat. Removes toxic substances from foods upon arrival from blood stream. Stores excess nutrients from blood (sugar & vitamins). Cannot live without. • GALL BLADDER— stores bile between meals. Secretes bile into SI. Can live without. Gall stones form when cholestrol content of bile comes out of solution (crytallizes)…oh my! • PANCREAS– secretes pancreatic juices which contain enzymes (i.e., lactase is an example) and buffering solution (raises pH). Can not live without SUMMARY - Digestion • • • • • • Mouth Phyarnx Esophagus Stomach Small Intest. Large Intest. • Pancreas • Liver • Gall Bladder