CHAPTER 9 DIGESTION ABSORPTION AMYLASE BILE COLON DEFECATION
CHAPTER 9: DIGESTION
ABSORPTION AMYLASE BILE COLON DEFECATION DIGESTION DUODENUM EPIGLOTTIS ESOPHAGUS FECES GLANDS HCL HYDROLYSIS LIPASE LIVER MALTASE MOUTH NEUTRALIZE NUCLEASE NUCLEOSIDASE PANCREAS PEPSIN PEPTIDASE PERISTALSIS PHARYNX RECTUM SALIVA SPHINCTER STOMACH TRYPSIN
Digestive Structures and Functions ØDigestion is the chemical breakdown of food by enzymes. ØPhysical digestion is mixing, churning and emulsifying of food ØDigestion involves hydrolytic enzymes which work at specific p. H’s ØAny molecules not digested and not absorbed are considered waste and are excreted via the rectum.
Mouth ØTeeth for tearing, chewing & grinding the food v Incisors for biting & tearing v Canines for tearing v Premolars and molars for grinding & chewing ØHard palate at front roof of mouth ØSoft palate at back roof of mouth v When swallowing the tongue pushes up the soft palate to close off the nasal cavity so food goes down towards esophagus ØUvula may be involved in creating a good seal for nasal cavity during swallowing ØTonsils involved in immunity ØTongue for mixing food with saliva
Salivary Glands & Swallowing Ø Salivary glands secrete water, mucus, and salivary amylase Ø Salivary amylase digests starch to maltose by hydrolysis Starch + H 2 O Salivary amylase maltose Ø Swallowing 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)
Stomach ØSmooth muscle causes peristalsis down the esophagus and it continues in the stomach to churn food with acid ØFood enters the stomach via the cardiac sphincter ØGastric juices are secreted from gastric glands when the GASTRIN hormone stimulates them. ØMucus secreted protects the lining of the stomach ØGastric glands secrete HCl to make a p. H of 2, water, pepsinogen ØBacteria can be killed by stomach acid ØPepsinogen is converted to pepsin in the presence of HCl. ØPepsin digests proteins to peptides Proteins + H 2 O pepsin peptides
Small Intestine Ø 3 parts = duodenum, jejunum, ileum ØAcid chyme enters duodenum via the pyloric sphincter ØPancreatic juices from pancreas enter via pancreatic duct ØBile from Liver and gall bladder enter via bile duct ØSodium bicarbonate (Na. HCO 3) from pancreas neutralizes acid chyme to a p. H = 8. 5 ØPancreatic enzymes and intestinal enzymes from the duodenum complete digestion of molecules; ie. Starch, protein, lipids, nucleic acids ØAbsorption of nutrients occurs along small intestine which has a high surface area due to villi ØGlucose, amino acids, phosphate group, pentose sugar, nitrogenous base enter blood capillary ØFatty acids and glycerol reform into a lipoprotein and are absorbed into the lacteal
Digestive Reactions in Small Intestine Pancreatic amylase Starch + H 2 O Maltose + H 2 O maltase Proteins + H 2 O trypsin Peptides + H 2 O peptidase Lipids emulsified by bile Lipids + H 2 O Glucose Peptides Amino Acids Fat Droplets Lipase Nucleic Acids + H 2 O Nucleotides+ H 2 O Maltose Nucleosidase Fatty Acids & Glycerol Nuclease Nucleotides Phosphate + Sugar + N. Base
Digestive Reactions in Small Intestine + H 2 O Pancreatic amylase + H 2 O maltase Proteins + H 2 O Peptides peptidase + H 2 O Lipids + H 2 O Amino Acids Fat Droplets Lipase Nucleic Acids + H 2 O Nucleotides+ H 2 O Maltose Nucleosidase Nucleotides
Large Intestine = Colon ØSite of water absorption ØHouses E. Coli for continued digestion and production of vitamins ØFeces solidifies as water is absorbed ØIndigestible fibre and other molecules exit body after the defecation reflex in the rectum
Defecation Internal sphincters are involuntary External sphincters are voluntary
Liver 1. Detoxifies blood 2. Regulates cholesterol 3. Stores glucose as glycogen 4. Stores vitamins and iron 5. Produces plasma proteins 6. Breaks down old red blood cells (hemoglobin) 7. Breaks down amino acids = produces urea 8. Produces bile from breakdown of hemoglobin Pancreas 1. Produces insulin and glucagon to regulate blood glucose 2. Produces digestive enzymes and Na. HCO 3 to neutralize acid chyme
Hepatic Portal Vein : carries absorbed nutrients from digestive tract to liver for processing and joining general circulation to rest of body.
Match Image Structure Function Contains rugae to expand hold food Detoxifies blood Brush border to increase surface area Closes opening to larynx when swallowing Site of water absorption May function in immunity but no real known function Feces stored and site of defecation Stores bile produced by liver Secretes a substance responsible for neutralizing acid chyme
Match Image Structure Function Secretes hormones that regulate blood sugar Produces urea and regulates cholesterol Site of complete digestion of food and absorption of molecules p. H = 2 Mucus protects lining Blood high in nutrients carried to liver through this Where small intestine and large intestine join Contains the lacteal for fat absorption When swallowing, it moves up to guide food into esphagus
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