Week 3 Notes
Week 3 Notes AN_SCI 3254 - 01
Popular in Physiology of Domestic Animals
Popular in Animal Science and Zoology
This 7 page Class Notes was uploaded by Nia on Saturday September 12, 2015. The Class Notes belongs to AN_SCI 3254 - 01 at University of Missouri - Columbia taught by Donald Spiers in Fall 2015. Since its upload, it has received 9 views. For similar materials see Physiology of Domestic Animals in Animal Science and Zoology at University of Missouri - Columbia.
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Date Created: 09/12/15
AnSci3254 Week 3 Notes 98 Deglutition Swallowing 0 Can t start once it s started 0 Takes food through the esophagus gt diaphragm gt stomach Peristaltic Wave Moving ring of contraction to help push food down 0 Starts in the pharynx l Pharynx Common passage for air and food Propels food to the esophagus Epiglottis Flap that folds over the trachea to prevent food from entering 0 Esophagus Muscular tube that passes through the thoracic cavity and the diaphragm to the stomach 0 Upper region Skeletal muscle voluntary 0 Lower region Smooth muscle involuntary l Stays smooth muscle from here until the end of the GI tract l Majority of the GI tract is smooth muscle Lower Gastroesophageal Sphincter Physiological barrier between esophagus and stomach 0 Sphincter Muscle regions that can be openedclosed to help with food passage Anatomically the same as the rest of the esophagus Physiologically and functionally very different 0 Constricted while the remainder of the esophagus is relaxed I Closed when not swallowing because otherwise stomach gases could cause burning heartburn 0 Relaxes and opens when the peristalsis waves reach it 0 Caves in because of esophageal connection below diaphragm l Caused by pressure difference I Subatmospheric Pressure in the thoracic cavity 5 to 10mmHg l Below atmospheric pressure I Keeps the lungs open I Abdominal Pressure 5 10 mmHg l Stomach liver etc puts pressure on this region I Pregnancy More pressure as the baby grows causes displaced terminal segment into the thoracic cavity l Stomach contents HCl gt esophagus gt Contractile spasms of smooth muscle l Heartburn l Newborns have no intrabdominal segment gt Causes regurgitation and spit up Vomiting Re ex 0 Very complexcoordinated re ex by vomit center in the medulla brain center 0 Actions 0 Relaxation of the muscles in the stomach and lower esophageal sphincter 0 Pyloric Sphincter between the stomach and small intestine closes I Don t want vomit to end up in the intestines where it can be absorbed into the blood Contraction of the abdominal muscles l Increases abdominal pressure 0 Expansion of the chest cavity l Decreases intrathoracic pressure I Increases the pressure difference which makes it easier to push things up Relaxation of the upper esophageal sphincter O O 99 Secretions of the stomach 0 3 Types of Cells 0 Mucus Neck Cells l Produce mucus lubricant 0 Parietal Cells l Produce HCl which is needed for protein digestion l HCl intrinsic factor I Intrinsic Factor Needed for Vitamin B 12 absorption 0 Chief Cells l Produce pepsinogen acted on by HCl to produce pepsin l Pepsin Protein digestion 0 Protein and fat digestion begins in the stomach I Carb digestion starts in the mouth 0 Gastric Lipase stimulates fat breakdown O Produced by mucosal lining and hydrolyzes fat into fatty acids glycerol 0 G Cells Produce gastrin in the stomach O Gastrin Increases secretion of HCl 0 D Cells Inhibit HCl production Stimulation of Gastric Secretions Cephalic Phase 0 Neural stimulation sight smell taste thought 0 Parasympathetic nervous system I Vagus nerve O Sends impulses to the stomach gt increased secretions motility O Stomach growling 0 Increased motility O Stomach getting ready for the food to come 0 Gastric Phase 0 Presence of food in the stomach causes an increase in HCl secretion and enzymes gastrin and pepsin 0 Mechanical stimulation distension 0 Chemical stimulation l Protein produces gastrin from antrum near pyloric sphincter O Gastrin causes increased HCl production 0 Alcohol high protein soup before eating I Stimulates stomach and release acid to prepare the stomach Intestinal Phase 0 Turns offreduces activity of the stomach 0 Enterogastric Re ex Release hormones to decrease motility slow down the stomach and reduce gastrin l Decrease HCl release 0 Doesn t require the brain at the local level 0 Central nervous systemEndocrine pathway 0 2 phases increase activity and 1 phase decreases it Ruminant Digestive System Digestive system large gtgt space for processing large quantities bulky forage 0 4 chambers of the stomach reticulum rumen omasum abomasum O Esophagus enters into the rumen 0 Reticulorumen Reticulum Rumen ideal ecosystem for microbes l Lots of bacteria Large fermentation vat for cellulose breakdown 6090 of digestion occurs here No secretory function Mainly absorptive Composed of smooth muscle vagus innervation Blood from the reticulorumen enters the hepatic portal vein and goes to the liver l Esophagus enters into the rumen O Omasum l Epithelium has lea ike folds that increase absorption gt surface area I Enormous absorptive ability 0 Abomasum true stomach I Similar to mono gastric stomach with some secretory ability I Closest to the pyloric sphincter Digestion O Carbohydrates cellulose I Take in and acted on by the microbes mainly anaerobic l Produces VFA acetate propionate butyrate I 6070 required energy for cow and absorbed across the rumen wall 0 Protein Digested by microbes 0 Lipids Broken down by microbes Microbes in rumen synthesize all B Complex vitamins and all essential amino acids Vertebrate Fermenters Foregut 0 Ruminants sheep cattle goats O Nonruminants kangaroos hippos Hindgut have fermenting microbes in the area of the large intestine and cecum O Rabbits horses zebras rhinos 0 Further down than foregut fermenters Midgut Between the foregut and hindgut 0 Mainly fish 0 Based on fermentation vat location 0 Not only ruminants have fermentation vats 0 Depend on the bugs in the stomach Small Intestine site of most absorption 0 Duodenum J ejunum Ileum 0 Very long 0 Villus center contains capillary network and lymphatic vessel 0 Secretin and cholecystokinin CCK released from the duodenum Actions 0 Decreased stomach motility O Decreased gastrin release 0 Decreased HCl secretion 910 Enterogastric Re ex High fat meal eggs and milk may be in the gut after 6 hours 0 High carb meals will be out in 3 hours 0 Fat keeps material in the stomach longer Motility Duodenum and small intestine Mixing contractionsegmentation O Segmentation Oscillating contractionrelaxation of smooth muscle 0 Chyme divided into segments forced up and down and mixed 0 Contractions that mix food and material with segmentation Propulsive Contraction Propel segments from one region to another 0 Local distention produces contraction of distended portion and relaxation of forward region I Distention caused by lots of food or chyme in the area 0 Mediated via myenteric plexus l Myenteric Plexus Internal network Doesn t need the vagus nerve 0 External nerve involvement autonomic nervous system involuntary l Parasympathetic vagus increases contraction activity I Stimulated by hostility l Sympathetic causes a decreased amount of contraction activity I Fight or ight Digestion in the small intestine Pancreas produces enzymes O Proteases proteolytic Breakdown protei O Amylases starch splitting 0 Lipases fat breakdown O Bicarbonate buffer so acid doesn t create ulcers 0 Opens into the duodenum near common bile duct gallbladder produces bile Carbohydrates in the GI tract 0 Both salivary and pancreatic amylases O Glucose produced from this is taken up via active transport 0 Protein 0 Digestion begins in the stomach with pepsin 0 Pancreatic proteolytic enzymes 0 Amino acids produced are taken up via active transport Lipids 0 Need to be broken down and absorbed 0 Bile from liver stored in gallbladder l Acts as a detergent l Breaks down fat decreases surface tension emulsification breakdown of fats 0 Pancreatic lipase furthers the breakdown of fat and produces free fatty acids glycerol 0 Occurs in the lumen of the small intestine Bile salts gtgt micelles FFA monoglycerides cholesterol gtgt enter solution otherwise they would be droplets of fat gtgt diffuse across membrane Triglycerides reformed in the epithelial cells and encased in protein coat chylomicrons O Chylomicrons are extruded with ATP and enter lacteals lymphatic system I Fats have to enter the lymphatic system 0 All fat is digestedabsorbed in the upper part of the small intestine Re exes of the Small Intestine Gastroileal stimulatory Starts in the stomach gt ends in the ileum 0 Increased stomach emptying causes an increase in contractions of the ileum 0 Ileogastric inhibitory Starts in the ileum gt ends in the stomach O Distention of ileum causes decreased stomach motility 0 Intestino intestinal inhibitory Muscle activity stops 0 Large distentions wall injury bacterial infection causes complete reduction in motor activity I Everything will slow own and sit there gt can t get rid of material I Local re e Ileocecal Valve Sphincter that is normally closed 0 Prevents back ow of fecal contents into the small intestine O Distended cecum causes an increase in sphincter contraction Large intestine storage and concentration of feces no digestive enzymes 0 Functions 0 Absorption of water and electrolytes l Na is actively transported out into the blood followed by water I Osmotic Drag water goes wherever the osmotic concentration goes 0 Storage of feces 0 Fermentation of organic matter I Major determinant of colon size I Provides some energy VFA hindgut fermenters l Colonic fermentation found in horses rabbits rats swine guinea pigs 0 Concentrate feces to prevent diarrhea Begins at cecum blind sac O Cecum Very important in horses Contains microorganisms that aid in fiber breakdown I Where most of the digestion occurs 0 Regions of the large intestine O Ascending colon 0 Transverse colon O Descending colon 0 Terminates at rectum and anus Horses have the largest colon and dogs have the shortest Longitudinal muscles of the large intestine are incomplete 0 Walls folded into sacs hausfrau due to circular muscles 0 Movement 0 Segmentation not propulsive mixing to help with salt and water removal I Very slow 1 every 30 minutes 0 Mass movement I 3 4 times per day 0 Large increase in motility O Simultaneous contraction transversedescending colons 0 Propelled 13 34 length colon few seconds Diarrhea 0 Causes most deaths around the world large loss of uid 0 Causes 0 Fluid enters colon faster than it can be absorbed l Normally 2 liters of water can be absorbed per day across the colon l Drink 26 liters per hour gtgt 15 liters per hour output from rectum l Enteritis Infected GI tract large intestine and distal end of ileum l Mucosa irritated by bacteria or virus I Increases section rate from the blood I Increases motility gt large uid output l Cholera Toxin outpouring large volume isotonic solution gt jejunum ileum colon l Causes death in 1 day I Only way to treat replace uid and electrolytes 0 Diarrhea of intestinal origin l Contents delivered at a normal rate but the colon isn t absorbing l Magnesium sulfate laxative poorly absorbed solute
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