Digestion Anatomy and Physiology
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Date Created: 09/25/14
Di gestion reductionbreakdown of feed particles for absorption into the blood to support body functions 2 categories o Digestive organs that form the tube that runs from the mouth to the anus I Digestive tract gastrointestinal tract GIT Gastroenteric tract Alimentary canal o Accessory digestive organs Palatable acceptable to eat Di gestible able to be broken down and absorbed Species Variation o Structure and function of GIT varies depending on the diet of the animal I Herbivores plant eating animals cattle sheep goats horse rabbits I Carnivores meat eating animals cats birds of prey I Omnivores plant and meat eating pigs chickens and humans o Monogastric animals 1 simple stomach I Humans horses dogs cats pigs o Foregut FermentersRuminants I 3 mixing and fermentation chambers before 1 true stomach chamber I Cows o Hindgut Fermenters I Fermentation occurs in the large intestines and cecum I Horses rabbits Digestive Tract Functions o Prehend grasp food with the lips teeth beak or claws o Ingest food and uid o Transport food and uid o Masticate chew vertical or lateral jaw movements mechanically grind food o Chemically digest food o Absorb nutrients and water o Eliminate waste Basic plan of GI o Salivary glands o Mouth o Esophagus o Stomach o Small intestine pancreas and liver o Cecum and large intestine or colon o Rectum Mouth o Prehend food o Initiate mechanical digestion I Breaks food into smaller particles that increase the surface area available for exposure to the enzymes involved in chemical digestion o Initiate chemical digestion I Salvia is produced by paired glands and added to food as it is chewed I Saliva provides moisture to soften and shape food into a form that is more readily swallowed I Saliva provides enzymes that breakdown food I Saliva provide ions o Move food toward pharynx for swallowing or deglutition o Teeth shape I Herbivore at surfaces Good for plant and grain material I Carnivore pointed slightly curved toward back of mouth Good for holding prey tearing cutting shredding o Ruminants I Dental pad think firm connective tissue instead of upper front teeth helps to grind feed I Salivary glands produce 100150 liters of salviaday Lubricate feed provide liquid for the bacterial and protozoal population buffer the rumen pH 6268 and recycle nitrogen and minerals Esophagus o Muscular tube transports the food from mouth to the stomach o As the stomach expands a fold of the stomach against the esophagus closes the lower end of esophagus I Reduces the risk of re ux I The closures is strong enough to prevent re ux or vomiting horse rabbit o Carnivores and Omnivores I Monogastric 1 stomach compartment acidic o Herbivores I Monogastric 1 stomach compartment horses 4 gallons rabbits I Ruminant 4 stomach compartments cattle more than 50 gallons sheep more than 12 gallons goats Monogastric Stomach o Location left upper quadrant of abdomen o Functions I Digestion Chemical Mechanical I Limited absorption I Temporary storage Ex pi gs 24 hrs for emptying of the stomach Gastric Glands Line the Stomach o Mucous cell secretes protective mucus o Parietal cell secretes hydrochloric acid o Chief cell secretes pepsinogen o G cell secretes gastrin Small Intestine o 3 segments I Duodenum 1st short segment that leaves the stomach Receives secretions of enzymes from he pancreas gallbladder and liver I J ejunum longest part I Ileum end portion o Functions I Di gest chemical and mechanical I Transport food I Absorb nutrients o Digestion and Absorption I Diffuse or are transported intact across the small intestine wall Electrolytes Water Vitamins I Diffuse passively across wall actively transported across wall Carbs Proteins Fats Pancreas o Secretes enzymes and bicarbonate through a duct into the small intestines o Enzymes digest carbs lipids and protein o Bicarbonate neutralizes incoming gastric acid o Position immediately below the diaphragm over the stomach in the abdomen but it s protected by the ribcage o Function ultimate multi tasking organ I Di gestive produces bile and eliminates waste hormones antibiotics I Vascular I Metabolic make store and breakdown carbs make store and breakdown lipids and proteins Gallbladder o Location tucked between the liver and small intestines o Function storage site for bile between meals o No gallbladder for horses Large Intestines o Cecum a blind ended pouch o Colon longest part o Rectum short terminal segment of the digestive tract o Function I Absorb water compact fecal matter I Absorb vitamins I Secrete mucus I Transport fecal matter I Store fecal matter I Monogastric herbivores absorb nutrients and perform fermentation I Carnivores simple tubular colon poorly developed cecum I Nonruminant Herbivores extensive colon and cecum horses guinea pigs rats rabbits modifications of cecum and colon allow fermentative digestion in hindgut Rectum o Last portion of large intestine o Mucus secreting glands that lubricate and aid the passage of contents o Terminal opening of the GIT o Internal and external muscle sphincters I Internal sphincter unconscious control I External sphincter voluntary Ruminant 4 connected stomach components cattle sheep goats o The main function of the complex stomach is to allow the animal to use roughage cellulose as an energy source o Microbial populations living in the 1st three compartments of the ruminant stomach ferment feed I Foregut Fermenter in front of the gut o A ruminant typically fills the rumen rapidly taking little to no time to chew its meal and then finds a place to rest and chew Ruminants o Esophagus bi directional o Rumination chewing cud they chew their food lateral jaw movements swallow their food regurgitate it re chew and then re swallow it o Eructation burping fermentation in the ruminant stomach chambers produces gases cow 3050 Lhr sheep 5 Lhr which must be expelled by burping 12 timesmin o Bloat over distention of rumenreticulum with gas Cow Stomach o Forestomach I Reticulum 25 gall I Rumen 4060 gall I Omasum 415 gall o True Stomach acidic I Abomasum 47 gall Reticulum o Looks like honeycomb when cut open o Smallest lst compartment Located just below the entrance of the esophagus heavy objects fall into the reticulum potential for migration Lining composed of honeycomb arrangement of folds separated from the Rumen by the ruminoreticular fold Looks like a shag carpet if cut open Largest compartment Extends from the diaphragm to the pelvis filling the entire left side of the abdomen Series of muscular sacs separated by muscular folds that aid in mixing of contents Warm 100 108 F dark and anaerobic with pH of 58 to 64 ideal environment for bacteria protozoa and fungi 150 billion microorganisms per teaspoon Fermentation Vat I The enzymatic breakdown of an energy rich compound in an anaerobic environment Fermentation the enzymatic breakdown of an energy rich compound in an anaerobic environment Characteristics I Hugestratified never empties rhythmic contractions I Organization At the top gases CO2 amp CH4 In the middle fiber mat today s hay At the bottom uid fine particles dense concentrates grain and yesterday s hay Reticuloruminal Contractions 2 3x every 2 minutes 0 O 0 Allow built up CO Allow partially digested plant material to be regurgitated for further breakdown cud chewing Move feed particles that have been reduced in size by cud chewing and microbial action out into the omasum 2 and methane gas to be expelled from the rumen eructation Carbohydrates in Feed 0 O 0 Protein 0 Microbial fermentation and digestion Volatile fatty acids VFAs acetic acid butyric acid and propionic acid VFAs absorbed through the rumen wall into the bloodstream or they pass through the rumen for absorption into the omasum or abomasum I Converted to glucose adipose tissue milk fat and other components I VFAs provide as much as 5080 of the ruminant s total energy needs Methane gas carbon dioxide lactate I These gases must be expelled by regular reticuloruminal contractions eructation Protein and non protein nitrogen in ruminant diet I Microbial enzymes break down into proteins I Animo acids carbon dioxide and ammonia Ammonia absorbed through rumen wall and transported to liver to be converted to urea gt microbes use Rumen Degradable Protein to make protein gt microbes themselves are flushed into the small intestines to be digested as a source of protein o Some dietary protein escapes the rumen and is absorbed in the small intestines Rumen Undegradable Protein Vitamins o Microbes in the rumen also produce B complex vitamins and vitamin K for the ruminant Omasum o Right side of cow Looks like leavespages in a book if cut open Recticulorumen contractions move feed into the omasum Absorbs water bicarbonate ions remaining VFA s from the feed Breaks food particles down further Abomasum o True stomach acidic digestion o Low right side of the abdomen below and behind the omasum o Functions like the monogastric stomach o Hydrochloric acid pH 354 and digestive enzymes Small intestines o Measure 20x the length of the animal o Nutrients are digested and absorbed through villi into blood vessels Cecum o 10 of cellulose escapes fermentation in the rumen but is caught and digested in the cecum Large Intestines o Absorb water some bacterial digestion CalfLambKid Digestion o Newborn ruminant s digestive tract functions primarily as a monogastric digestive system o The abomasum is functional at birth but the rumen and reticulum are not yet functional o Nursing stimulates re ex contraction of the esophageal groove which allows milk to bypass the reticulum and rumen and pass directly through the omasum into the abomasum o The reticulum and rumen are bypassed until they are inoculated with bacteria and rumen papillae develop in response to diet Herbivores o Hindgut fermenters o Microbial breakdown and fermentation of roughage occurs after the stomach in the cecum and large intestines Avian Digestive Tract O O O O Ileum BeakMouth I Glands secrete salvia I Tongue moves feed to the pharynx for swallowing Esophagus Crop I Out pocketing of the esophagus I Feed and water are stored in the crop until the remainder of the digestive tract is ready to receive more food I When nearly empty the crop sends signals to the brain so that more feed is consumed Proventriculus I True glandular stomach I Grind crush and mix feed with digestive juices enzymes from PV I Grit vs teeth Small Intestines I Duodenum I J ejunum Ceca singular cecum I Blind pouches at the function of the small and large intestines I The size is in uenced by the species and diet ceca are larger when the bird consumes high fiber I Functions absorb water ferment coarse feed and produce B vitamins Large Intestines or colon I Re absorb water Rectum short Cloaca I Common orifice for waste elimination feces and urine copulation and egg laying in the females Vent