Y khoa - Dược - Chapter 33: The Digestive System

33The Digestive SystemLearning Outcomes (cont.)33.1 Describe the organs of the alimentary canal and their functions. 33.2 Explain the functions of the digestive system’s accessory organs.Learning Outcomes (cont.)33.3 Identify the nutrients absorbed by the digestive system and where they are absorbed.33.4 Describe the causes, signs and symptoms, and treatments of various common diseases and disorders of the digestive system.IntroductionDigestion – mechanical and chemical breakdown of foodsOrgans of digestionAlimentary canal organs form a pathway extending from the mouth to the anus Accessory organsCharacteristics of the Alimentary Canal Mucosa Epithelial tissueSecretes enzymes and mucusAbsorbs nutrientsSubmucosa – loose connective tissue, blood vessels, glands, and nervesCharacteristics of the Alimentary Canal Muscular layerSmooth muscleContracts to move materials through the canalSerosa or peritoneumVisceral peritoneum Parietal peritoneumCharacteristics of the Alimentary Canal (cont.)MovementsChurning ~ mixes substances Peristalsis ~ moves substances The MouthBuccal cavity Mechanical digestionStarts chemical digestionCheeks – hold food in mouthLips – judge temperature of foodThe MouthThe Mouth (cont.)Tongue Mixes and holds food between teethContains taste budsLingual frenulum Lingual tonsilsPalate Hard palateSoft palateUvulaLymphatic tissuePalatine tonsils Pharyngeal tonsils or adenoidsThe MouthThe Mouth (cont.)BackThe Mouth (cont.)Salivary glandsCellsSerous – watery fluidand amylaseMucousParotid glandSubmandibular glandSublingual glandThe Mouth (cont.)Teeth – decrease size of food particlesIncisors Cuspids or caninesBicuspids and molars PharynxFunctions Connects nasal cavity with oral cavity for breathingPushes food into esophagusDivisions NasopharynxOropharynxLaryngopharynxPharynxPharynx (cont.)Swallowing Soft palate rises; uvula covers opening between nasal and oral cavityEpiglottis covers larynx – keeps food outTongue presses against roof of mouth, forcing food into oropharynxPharynxPharynx (cont.)SwallowingMuscles in pharynx contract – forcing food toward esophagusEsophagus opensMuscles of pharynx push food through cardiac sphincterPharynxBackThe EsophagusConnects pharynx to stomachEsophageal hiatusCardiac sphincter Circular band of muscle Controls movement of food into stomachLower EsophagusUpper EsophagusThe StomachAbsorbsAlcoholWaterSome fat-soluble drugsStomachRugae – folds of the inner liningFunctionsReceives food Mixes bolus with gastric juices  chyme Starts protein digestionMoves food into small intestineThe StomachSectionsCardiac region Fundus Pyloric sphincter – controls movement into the small intestineStomachBody PylorusThe StomachLining – gastric glandsCells ~ mucous, chief, and parietalStimulated by Parasympathetic nervous system Gastrin – made by the stomachInhibited by cholecystokinin (CCK) made by the small intestineStomachBackThe Small IntestineFunctionsDigestionAbsorption of nutrientsSections DuodenumJejunumIleum Mesentery Small IntestineThe Small Intestine (cont.)Microvilli Intestinal glandsMucus and waterEnzymes Peptidases Sucrase, maltase, and lactase Intestinal lipaseStimulated byParasympathetic nervous systemStretching of the intestinal wallThe Small Intestine (cont.)Absorbs most nutrientsWall contracts to mix and propel chymeIleocecal sphincter – controls movement of chyme into cecum of the large intestineBackThe Large Intestine CecumVermiform appendix Ascending colon Transverse colonDescending colonSigmoid colonLarge IntestineThe Rectum and Anal CanalRectum – off sigmoid colonAnal canalEnd of rectumAnus Feces – left-over chymeDefecation reflexStimulated by mass movements Relaxation of anal sphinctersRectum & Anal CanalBackApply Your Knowledge1. Matching: ___ Buccal cavity A. Saliva___ Roof of mouth B. Mouth___ Grind food C. Bolus___ Adenoids D. Palate___ Water, enzymes, and mucus E. Bicuspids___ Mass of food mixed with saliva and mucus F. Pharyngeal glandDEFABBANSWER:Apply Your Knowledge2. What are the functions of the stomach?ANSWER: The stomach’s functions are to receive the bolus of food, mix it with gastric juice, start protein digestion, and move food into the small intestine. It also absorbs alcohol, water, and some drugs.Apply Your Knowledge3. Matching:___ Vermiform appendix A. Feces___ Crosses the abdomen B. Ascending colon___ Up right side of abdomen C. Anal canal___ S-shaped tube D. Defecation reflex___ Down left side of abdomen E. Sigmoid___ Leftover chyme F. Transverse colon___ Last section of rectum G. Cecum___ Allows anal sphincters to relax H. Descending colonHGFEDCBAANSWER:Super!Characteristics of the Digestive Accessory OrgansThe LiverHepatic lobules Smaller divisions of lobesMacrophagesHepatocytes – bileHepatic portal vein Part of liver’s function ~ store vitamins and ironTo LiverThe Liver (cont.)Hepatic duct Bile from liverMerges with cystic duct and forms common bile duct Common bile duct ~ delivers bile to duodenumTo LiverThe GallbladderOnly function is to store bileCholecystokinin stimulates gallbladder to release bileBile saltsBreak up large fat globulesIncrease absorption of fatty acids, cholesterol, and fat-soluble vitaminsTo GallbladderThe Liver (cont.)BackThe PancreasAcinar cells produce pancreatic juice Pancreatic amylasePancreatic lipase NucleasesTrypsin, chymotrypsin, and carboxypeptidaseThe Pancreas (cont.)Releases bicarbonate ions into duodenumStimulated to release enzymes byParasympathetic nervous systemSecretin and cholecystokininApply Your Knowledge1. What is the route of bile through the liver and gallbladder?ANSWER: Bile is made in the hepatocytes and leaves the liver through the hepatic duct. The hepatic duct merges with the cystic duct from the gallbladder to form the common bile duct, which delivers bile to the duodenum.Apply Your Knowledge2. What are the pancreatic enzymes and what do they do?ANSWER: They are:Pancreatic amylase – digests carbohydratesPancreatic lipase – digests lipidsNucleases – digest nucleic acidsTrypsin, chymotrypsin, and carboxypeptidase – digest proteinsGood Job!The Absorption of NutrientsNutrients – necessary food substancesCarbohydratesProteinsLipidsVitamins MineralsWaterThe Absorption of Nutrients (cont.)Carbohydrates Starches ~ polysaccharidesSimple sugarsMonosaccharides and disaccharides Excess glucose stored as glycogenCellulose – provides fiber or bulkThe Absorption of Nutrients (cont.)LipidsUsed to make energy when glucose levels are lowTriglycerides Most abundant Excess stored in adipose tissueCholesterol – essential for cell growth and functionThe Absorption of Nutrients (cont.)Vitamins Fat-solubleWater-solubleMinerals Found in bones and teethUsed to make enzymes, cell membranes, and proteinsProteinRequirements varyUsed for growth and tissue repair Apply Your KnowledgeTrue or False: ___ Carbohydrates are starches, simple sugars, and cellulose.___ Excess glucose is stored in the gallbladder as glycogen.___ Triglycerides are the least abundant lipids___ Linoleic acid is an essential fatty acid.___ A, D, E and K are water-soluble vitamins.___ Minerals are used by cells to make enzymes.FFFTTANSWER:Tlivermostfat-solubleImpressive!Aging and the Digestive SystemDecreased Motility Absorption Ability to detoxify bloodMore likely to develop ulcers and cancersSense of taste alteredDietary changes due toIsolationDepression Common Diseases and DisordersDisease/DisorderDescription AppendicitisInflammation of the appendix; can be life-threatening if not treated promptlyCirrhosisChronic liver disease; normal tissue is replaced with nonfunctional scar tissueCholelithiasis (gall stones)Hard deposits of cholesterol or bilirubin in the gall bladderCommon Diseases and DisordersDisease/DisorderDescription ColitisInflammation of the large intestine; can be acute or chronicColorectal cancerArises from lining of rectum or colon; curable if treated earlyConstipationDifficult defecationCrohn’s diseaseInflammatory bowel disease; typically effects small intestineCommon Diseases and Disorders (cont.)Disease/DisorderDescription DiarrheaWatery and frequent feces; usually self-limitingDiverticulitisInflammation of diverticulaDiverticulosis – diverticula with no inflammationGastritisInflammation of the stomach lining; “upset stomach”Common Diseases and Disorders (cont.)Disease/DisorderDescription HeartburnGastroesophageal reflux disease (GERD); stomach acids push into esophagusHemorrhoidsVaricose veins of rectum or anusHepatitis Inflammation of the liver; various typesHiatal herniaPortion of stomach protrudes into the chest through an opening in the diaphragmCommon Diseases and Disorders (cont.)Disease/DisorderDescription Inguinal herniaPortion of large intestine protrudes in the inguinal canal (where thigh and trunk meet) or, in males, into the scrotumOral cancerUsually involves the lips or tongue but can occur anywhere in the mouth; tends to spread rapidlyCommon Diseases and Disorders (cont.)Disease/DisorderDescription Pancreatic cancerFourth leading cause of cancer deaths in the U.S.Stomach cancer Commonly in cardiac portion of the stomach; occurs more frequently in Japan, Chili, and IcelandStomach ulcersBreakdown in lining of the stomachApply Your KnowledgeMatching:___ Inflammation of the large intestine A. Heartburn___ Inflammatory bowel disease B. Hemorrhoids___ Watery and frequent feces C. Constipation___ Difficult defecation D. Crohn’s disease___ Inflammation of the stomach lining E. Colitis___ Inflammation of pouches in the intestinal wall F. Diarrhea___ GERD G. Gastritis___ Varicose veins of rectum H. DiverticulitisHGFDCBAEANSWER:Nice Job!In Summary33.1 The pathway of food through the alimentary canal starts with the mouth and continues through the pharynx, esophagus, stomach, small intestine, large intestine, and anal canal. In Summary (cont.)33.2 The accessory organs to the digestive system include the liver, gallbladder, and pancreas. 33.3 Nutrients absorbed by the body include carbohydrates, proteins, lipids, vitamins, minerals, and water. Most of the absorption takes place in the small intestine. In Summary (cont.)33.4 There are many common diseases and disorders of the digestive system with varied signs, symptoms, and treatments. Take all that is given whether wealth, love or language; nothing comes by mistake and with good digestion all can be turned to health. ~ George HerbertEnd of Chapter 33