THE DIGESTIVE SYSTEM - University Of Cincinnati
THE DIGESTIVE SYSTEMCOMPILED BY HOWIE BAUM
DIGESTIVESYSTEMPeople are probablymore aware of theirdigestive systemthan of any othersystem, not leastbecause of itsfrequent messages.Hunger, thirst,appetite, gas , andthe frequency andnature of bowelmovements, are allissues affecting dailylife.
The Digestive Tract Six Functions of the Digestive System1. Ingestion2. Mechanical processing3. Digestion4. Secretion5. Absorption6. Excretion
The Digestive Tract Ingestion– Occurs when materials enter digestive tract via themouth Mechanical Processing– Crushing and shearing– Makes materials easier to propel along digestivetract Digestion– The chemical breakdown of food into small organicfragments for absorption by digestive epithelium
The Digestive Tract Secretion– Is the release of water, acids, enzymes, buffers, andsalts– By epithelium of digestive tract– By glandular organs Absorption– Movement of organic substrates, electrolytes,vitamins, and water– Across digestive epithelium tissue– Into the interstitial fluid of digestive tract Excretion– Removal of waste products from body fluids– Process called defecation removes feces
AN INTRODUCTION TO THE DIGESTIVE SYSTEM The Digestive Tract Also called the gastrointestinal (GI) tract oralimentary canal Is a muscular tube Extends from our mouth to the anus Passes through the pharynx, esophagus, stomach,and small and large intestines
The digestive system is oneof the most clearly defined inthe body.It consists of a longpassageway, the digestivetract, and associated glands.These include the liver andpancreas, which areconnected to the main tractby ducts, or tubes, andempty their products, suchas enzymes, into the tract.
Major Organs ofthe Digestive TractOral Cavity (Mouth)Ingestion, mechanical processing withaccessory organs (teeth and tongue),moistening, mixing with salivary secretionsPharynxMuscular propulsion of materials intothe esophagusEsophagusTransport of materials to the stomachStomachChemical breakdown of materials by acidand enzymes; mechanical processingthrough muscular contractionsSmall IntestineEnzymatic digestion and absorption ofwater, organic substrates, vitamins, and ionsLarge IntestineDehydration and compaction of indigestiblematerials in preparation for eliminationAnus
Accessory Organs ofthe Digestive SystemTeethMechanical processing bychewing (mastication)TongueAssists mechanical processingwith teeth, sensory analysisSalivary GlandsSecretion of lubricating fluidcontaining enzymes thatbreak down carbohydratesLiverSecretion of bile (importantfor lipid digestion), storage ofnutrients, many other vitalfunctionsGallbladderStorage and concentration ofbilePancreasExocrine cells secrete buffersand digestive enzymes;Endocrine cells secretehormones
Your intestines are about 22 feet long– the surface areawould cover almost 3000 square feet, the size of atennis court!There’s a good reason for its size – Our digestive system is vital for our survival. It’s our nutrient feed Our main defense system Our main elimination route for waste The location for a million different vital biochemicalprocesses.
The Oral Cavity Functions of the Oral Cavity1. Sensory analysis Of material before swallowing2. Mechanical processing Through actions of teeth, tongue, and palatalsurfaces3. Lubrication Mixing with mucus and salivary glandsecretions4. Limited digestion Of carbohydrates and lipids
Figure 24-7a The Salivary Glands.Parotid ductOpenings ofsublingualductsLingualfrenulumOpening of leftsubmandibularductSalivary GlandsParotid salivaryglandSublingualsalivary glandSubmandibularsalivary glandSubmandibularductThe oral cavity is bounded by the teeth, tongue, hard palate, and soft palate.These structures make up the mouth and play a key role in the first step ofdigestion, called ingestion.This is where the teeth and tongue work with salivary glands to break downfood into small masses that can be swallowed, preparing them for thejourney through the alimentary digestive-oral-cavity#saliva
Saliva Moistens Food &Begins the Process ofChemical DigestionSaliva secreted by salivaryglands aids the mechanicaland chemical process ofdigestion.Saliva is about 99% waterand not only moistens foodbut cleanses the mouth,dissolves food chemicals sothey can be tasted, andcontains enzymes that startthe chemical breakdown ofstarchy foods.There are three pairs ofsalivary glands: parotid,sublingual, andsubmandibular (also calledthe submaxillary gland).
The Tongue Creates a Bolus of food so it can travel down thePharynx and Esophagushttps://www.youtube.com/watch?time continue 13&v 6PymJS97XdY
Peristaltic Waves MoveNutrients and WasteThrough the Intestines
Peristalsis Consists of waves of muscularcontractions Moves a bolus along the length ofthe digestive tract Peristaltic Motion1. Circular muscles contract behindbolus While circular muscles ahead ofbolus relax2. Longitudinal muscles ahead of boluscontract Shortening adjacent segments3. Wave of contraction in circularmuscles Forces bolus forward
STOMACHSTRUCTUREThe stomach is the widestpart of the digestive tube.It is a muscular-walled, Jshaped sac in which food isstored, churned, andmixed with gastric juicessecreted by its lining.This process beginsmoments after food entersthe stomach from theoesophagus, through thegastro-oesophagealjunction.Gastric juices includedigestive enzymes andhydrochloric acid, whichnot only breaks down foodbut also kills potentiallyharmful microbes.
Food that is chewed in theoral cavity then swallowedends up in the stomachwhere it is further digestedso its nutrients can beabsorbed in the smallintestine.The salivary glands, liverand gall bladder, and thepancreas aid the processesof ingestion, digestion, andabsorption.These accessory organs ofdigestion play key roles inthe digestive process. Eachof these organs eithersecretes or storessubstances that ugh ducts into thee/digestive-accessory-organs#salivaalimentary canal.
The Liver SecretesBile to Emulsify Fatsin the Small IntestineThe liver is one of thelargest organs in the bodyand it is continuouslyproducing bile.This yellowish-brown fluidaids chemical digestion byemulsifying fats in theduodenum.Bile flows out of the liver intothe right and left hepaticducts, into the commonhepatic ducts, and towardthe small intestine to helpwith digestion and theabsorption of fats.
The Gall BladderStores BileIf bile is notimmediately needed fordigestion, it flows upthe cystic duct to thegall bladder.The gall bladder is agreen, pear-shaped sacabout 10 cm or 4 in.long that stores andconcentrates excessbile secreted by theliver.Bile is released by thegall bladder as neededinto the small intestine.
The pancreas secretespancreatic juice, a mix ofdigestive enzymes, water,buffers (bicarbonates),and electrolytes producedby acinar and epithelialcells.Pancreatic juice drainsthrough the mainpancreatic duct (duct ofWirsung) into thecommon bile duct andthen into the smallintestine.There it buffers stomachacids and breaks downprotein, fats, andcarbohydrates.
Nutrients In, Waste Out:How the Human Body AbsorbsNutrients and Eliminates WasteVilli that line the walls of the smallintestine absorb nutrients intocapillaries of the circulatory systemand lacteals of the lymphaticsystem.Villi contain capillary beds, as wellas lymphatic vessels calledlacteals.Fatty acids absorbed from brokendown chyme pass into the lacteals.Other absorbed nutrients enter thebloodstream through the capillarybeds and are taken directly to theliver, via the hepatic vein, forprocessing.Nutrients In, Waste Out: How theHuman Body Absorbs Nutrients andEliminates Waste
Figure 24-3 The Structure of the Digestive Tract (Part 2 of aVilliMucosal glandsSubmucosal ernaSerosa(visceralperitoneum)Lymphatic vesselArtery and veinSubmucosalplexusCircular musclelayerMyenteric plexusLongitudinalmuscle layer
Chyme passes from the smallintestine through the ileocecalvalve and into the cecum of thelarge intestine.Any remaining nutrients andsome water are absorbed asperistaltic waves move thechyme into the ascending andtransverse colons.This dehydration, combinedwith peristaltic waves, helpscompact the chyme.The solid waste formed is calledfeces.It continues to move throughthe descending and sigmoidcolons.The large intestine temporarilystores the feces prior toelimination.
The body expels wasteproducts from digestionthrough the rectum and anus.This process, calleddefecation, involves contractionof rectal muscles, relaxation ofthe internal anal sphincter, andan initial contraction of theskeletal muscle of the externalanal sphincter.The defecation reflex is mostlyinvoluntary, under thecommand of the autonomicnervous system.But the somatic nervoussystem also plays a role tocontrol the timing ofelimination.https://www.youtube.com/watch?v exsrs0STtU 3-1/2 minutesWHAT HAPPENS IN 1 MINUTEhttps://www.youtube.com/watch?v GjSTiWcqyFI
THE END !!
Saliva Moistens Food & Begins the Process of . Chemical Digestion. Saliva secreted by salivary glands aids the mechanical and chemical process of digestion. Saliva is about 99% water and not only moistens food but cleanses the mouth, dissolves food chemicals so they can be tasted, and
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Label The Digestive System. 5. 6 . Kids Health Digestive System. 8 peristalsis major filter of body produces insulin stores bile filters absorbs food mechanical and chemical produces extra white blood cells absorbs water Name the organs in the Digestive System. 9
ruminant stomach occupies almost 75 percent of the abdominal cavity, filling nearly all of the left side and extending significantly into the right side. The relative size of the four compartments is as follows: the rumen and reticulum comprise 84 percent of the volume of the total stomach, the omasum 12 percent, and the abomasum 4 percent.File Size: 318KBPage Count: 8Explore further4 Grains You Can Feed Your Livestock - Hobby Farmswww.hobbyfarms.comUnderstanding the Ruminant Animal Digestive System .extension.msstate.eduHow the Digestive System Works in a Cow & Other Ruminants .proearthanimalhealth.comRuminant Digestive System - Basic Concept, Examples .www.vedantu.comThe ruminant digestive system - Extension at the .extension.umn.eduRecommended to you based on what's popular Feedback
