3 Digestive Structures and Functions Digestion is the chemical breakdown of food by enzymes.Physical digestion is mixing, churning and emulsifying of foodDigestion involves hydrolytic enzymes which work at specific pH’sAny molecules not digested and not absorbed are considered waste and are excreted via the rectum.
4 Mouth Teeth for tearing, chewing & grinding the food Incisors for biting & tearingCanines for tearingPremolars and molars for grinding & chewingHard palate at front roof of mouthSoft palate at back roof of mouthWhen swallowing the tongue pushes up the soft palate to close off the nasal cavity so food goes down towards esophagusUvula may be involved in creating a good seal for nasal cavity during swallowingTonsils involved in immunityTongue for mixing food with saliva
5 Salivary Glands & Swallowing Salivary glands secrete water, mucus, and salivary amylaseSalivary amylase digests starch to maltose by hydrolysisStarch + H2O maltoseSalivary amylaseSwallowing involves the soft palate moving up to block nasopharynx (to nasal cavity) & the epiglottis moving down to block the opening to the lungs (the glottis)
7 Stomach Proteins + H2O peptides Smooth muscle causes peristalsis down the esophagus and it continues in the stomach to churn food with acidFood enters the stomach via the cardiac sphincterGastric juices are secreted from gastric glands when the GASTRIN hormone stimulates them.Mucus secreted protects the lining of the stomachGastric glands secrete HCl to make a pH of 2, water, pepsinogenBacteria can be killed by stomach acidPepsinogen is converted to pepsin in the presence of HCl.Pepsin digests proteins to peptidesProteins + H2O peptidespepsin
9 Small Intestine3 parts = duodenum, jejunum, ileumAcid chyme enters duodenum via the pyloric sphincterPancreatic juices from pancreas enter via pancreatic ductBile from Liver and gall bladder enter via bile ductSodium bicarbonate (NaHCO3) from pancreas neutralizes acid chyme to a pH = 8.5Pancreatic enzymes and intestinal enzymes from the duodenum complete digestion of molecules; ie. Starch, protein, lipids, nucleic acidsAbsorption of nutrients occurs along small intestine which has a high surface area due to villiGlucose, amino acids, phosphate group, pentose sugar, nitrogenous base enter blood capillaryFatty acids and glycerol reform into a lipoprotein and are absorbed into the lacteal
10 Digestive Reactions in Small Intestine PancreaticEnzymeStarch + H2O MaltosePancreatic amylaseMaltose + H2O GlucosemaltaseS.I. EnzymeProteins + H2O PeptidestrypsinPancreaticEnzymePeptides + H2O Amino AcidspeptidaseS.I. EnzymeLipids emulsified by bile Fat DropletsLiver & Gall BladderLipids + H2O Fatty Acids & GlycerolLipasePancreaticEnzymePancreaticEnzymeNucleic Acids + H2O NucleotidesNucleaseNucleotides+ H2O Phosphate + Sugar + N. BaseNucleosidaseS.I. Enzyme
12 Large Intestine = Colon Site of water absorptionHouses E.Coli for continued digestion and production of vitaminsFeces solidifies as water is absorbedIndigestible fibre and other molecules exit body after the defecation reflex in the rectum
13 Defecation Internal sphincters are involuntary External sphincters are voluntary
14 Liver Pancreas Detoxifies blood Regulates cholesterol Stores glucose as glycogenStores vitamins and ironProduces plasma proteinsBreaks down old red blood cells (hemoglobin)Breaks down amino acids = produces ureaProduces bile from breakdown of hemoglobinPancreasProduces insulin and glucagon to regulate blood glucoseProduces digestive enzymes and NaHCO3 to neutralize acid chyme
15 Hepatic Portal Vein : carries absorbed nutrients from digestive tract to liver for processing and joining general circulation to rest of body.
16 Contains rugae to expand and hold food Detoxifies blood Match ImageStructureFunctionContains rugae to expand and hold foodDetoxifies bloodBrush border to increase surface areaCloses opening to larynx when swallowingSite of water absorptionMay function in immunity but no real known functionFeces stored and site of defecationStores bile produced by liverSecretes a substance responsible for neutralizing acid chyme
17 Secretes hormones that regulate blood sugar Match ImageStructureFunctionSecretes hormones that regulate blood sugarProduces urea and regulates cholesterolSite of complete digestion of food and absorption of moleculespH = 2Mucus protects liningBlood high in nutrients carried to liver through thisWhere small intestine and large intestine joinContains the lacteal for fat absorptionWhen swallowing, it moves up to guide food into esphagus