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DIGESTION – the process of changing foods into simpler soluble forms to be absorbed by body ALIMENTARY CANAL Digestive tract or gastrointestinal tract (GI Tract). A 30 ft. tube from mouth to anus. Functions of the Digestive System Physical breakdown Chemical digestion of food Absorb nutrients Eliminate waste products Lining of the Digestive System PERITONEUM – double-layered serous membrane that lines the abdominal cavity Parietal layer lines the abd. cavity Visceral layer lines the organs of the abd. cavity Peritoneum has 2 “parts” Mesentery attaches to the posterior wall of abd. Greater omentum attaches to anterior wall of abd. Peritonitis inflammation/infection of the peritoneum 4 Layers of the GI Tract 1. Mucosa layer secrets a “slimy mucus” This mucus coats the food AND helps protect the organs from the corrosive enzymes in the GI tract 2. Sub mucosa layer lies under mucosa layer and contains blood vessels and nerves 3. 4. Circular muscle layer bands of muscles that are circular Longitudinal muscle layer bands of muscles that run length wise on the GI tract The muscle layer help perform “peristalsis” Wave like motion that pushes food through the GI tract Structure of Organs of Digestion MOUTH Food enters digestive system through mouth “buccal cavity” Inside of mouth covered with mucous membrane Roof of mouth is HARD PALATE (bone) and soft palate UVULA – flap that hangs off soft palate – prevents food from going up the nose when you swallow TONGUE Helps in chewing and swallowing Made of skeletal muscle > 9000 taste buds (papillae) on the surface Also sensitive to heat, cold and pressure SALIVARY GLANDS Three pairs of glands PAROTID – largest salivary glands Secrete saliva (about 3 qts. per day) Salvia is made up of: 1. mucus to coat the food 2. ptyalin (amylase) starts chemical breakdown of food Amylase breaks down carbohydrates or “starches” TEETH GINGIVA – gums MASTICATION – chewing Adult mouth has 32 teeth Teeth are covered with enamel- hardest substance in the body Inside the tooth is pulp- contains nerves and blood vessels As we chew and mix saliva with our food we create a “bolus” a soft, ball of food pliable ESOPHAGUS Connects pharynx an stomach Muscular tube, 10” long “epiglottis” allows passage of food into the esophagus CARDIAC SPHINCTER – circular muscular valve controls passage of food into stomach AND prevents food from re-entering the esophagus STOMACH Upper part of abdominal cavity Divided into 3 parts: 1. Fundus upper part 2. Greater curvature 3. Pyloric lower part SPHINCTER – circular muscle, valve PYLORIC Controls passage of food into the small intestines AND prevents food from coming back into the stomach When the stomach is not distended with food, it “folds” in on itself, These folds are called “Rugae” The stomach has millions of “gastric glands” which secrete gastric juices or enzymes to help digest food As food is chemically digested it turns into a semi-liquid mixture: “Chyme” Chyme enters the small intestines SMALL INTESTINE DUODENUM – first segment of small intestines, 12” long Very important because this is where the common bile duct, liver and pancreas dump their digestive enzymes!!! JEJUNUM – next section, 8 ft. long ILEUM – final portion, 10-12 feet long Don’t Jump In!!! Small intestines prepare the chyme for absorption There are tiny projections from the wall of the small intestines that increase the absorption area called: “villi” Villi are filled with blood vessels and absorb the nutrients Villi of the Ileum Undigested parts of chyme go to the LARGE INTESTINES via the ileocecal valve The small areas below the ileocecal valve are the Cecum and appendix Cecum and Appendix They have no known function Empty slowly and can fill with bacteria causing appendicitis LARGE INTESTINE also called the colon Approx 2” in diameter, has 3 parts: Ascending colon Transverse colon Descending colon The last part of the descending colon curves back into the abd. and forms an “S” called the Sigmoid colon The last 7-8 inches of the colon is called the rectum External opening is the anus Hemorrhoids enlarged rectal veins Accessory Organs of Digestion They don’t come in contact with the food 1. PANCREAS Located behind stomach Exocrine function – secretes digestive enzymes into duodenum Endocrine function secretes Insulin LIVER Largest organ in the body Located upper right quadrant Main function is to produce bile about 800-1000 ccs of bile per day The liver has other functions: store glucose in the form of GLYCOGEN Detoxify alcohol, drugs and other harmful substances Manufacture blood proteins (fibrinogen and prothrombin) Liver is connected to gallbladder and small intestine by ducts If the “common bile duct” becomes blocked, bile backs up in the liver and a person may become “Jaundiced” yellow tint to the skin because the liver can’t metabolize all the bile GALL BLADDER Small green organ, inferior surface of the liver Stores and concentrates bile until needed by the body When fatty foods digested, bile released by gallbladder DIGESTION In the mouth… Teeth: begin mechanical breakdown of the food Saliva: mucus softens and coats the food to make it easier to swallow PTYALIN in saliva converts starches into simple sugar This creates a BOLUS soft, pliable ball, it slides down esophagus Swallowing begins as a voluntary action, but as the bolus hits the esophagus, the process becomes involuntary In the esophagus: Peristalsis begins here and the food continues to be coated with mucus In the stomach… gastric (digestive) juices are released About 2-3 quarts per day stomach walls churn and mix the digestive juices and food to create the chyme takes 2-4 hours for stomach to empty Enzymes released by the stomach: 1. protease 2. pepsin both of these breakdown proteins (remember p and p) 3. Hydrochloric Acid (HCL acid) kills the bacteria in our food small amount of chyme enters duodenum at a time - controlled by pyloric sphincter In the small intestine… addition of enzymes from pancreas and bile from liver/gallbladder digestion occurs is completed and absorption Enzymes from the Small Intestines 1. Maltase 2. Lactase 3. Sucrase these all break down glucose 4. lipase breaks down fats 5. peptidases break down proteins Enzymes from the Liver/Gall Bladder 1. Bile breaks down fats Enzymes from the Pancreas 1. protease breaks down proteins 2. amylase breaks down carbs/starches 3. lipase breaks down fats 4. enzymes to neutralize acidic chyme Absorption by the villi can only occur when the end products of digestion are in these forms: 1. Carbohydrates are converted to glucose 2. Proteins are converted to amino acids 3. Fats are converted to fatty acids and glycerol Portal Circulation How does the liver work as a filter??? “portal veins” picks up the blood from the villi blood is transported to the liver blood is filtered dumped back into systemic circulation The In the large intestine… regulation of H2O balance by absorbing large quantities of H2O back into bloodstream If we absorb to much H2O of the waste material, what do we get? Constipation If we absorb to little H2O out of the waste material, what do we get? diarrhea We have bacteria in our intestines What is the most common type? E. coli It is harmless to us and helps decompose the undigested food/waste material It also helps make Vit. K Why do we need Vit. K? coagulation When this decomposition occurs, Flatulence or gas is produced We pass about 1-3 pints /day The gas of sulfur and methane give feces it’s odor Feces undigested semi-solid waste Feces is stored in the rectum Feces is stored in the rectum When the rectum becomes full, The defecation reflex is triggered Defecation is an involuntary action that we learn to control HEARTBURN Acid reflux burning sensation in throat/chest Rx – avoid chocolate, coffee, fried or fatty foods, stop smoking GERD: gastroesophageal reflux disease heartburn more than 2-3 times per week HIATAL HERNIA stomach protrudes above the diaphragm through the esophagus PYLORIC STENOSIS Narrowing of pyloric sphincter, found in infants S/S – projectile vomiting Rx – surgery to stretch pyloric sphincter CHOLECYSTITIS Inflammation of gallbladder CHOLELITHIASIS Gall stones Small ones may pass on their own Large ones can block the bile duct causes pain (back, shoulders) N/V after eating CHOLECYSTECTOMY surgically removed of gallbladder LAPAROSCOPIC CHOLECYSTECTOMY Small abdominal incisions (though belly button area) allow insertion of surgical instruments and small video camera Surgeon performs procedure by watching monitor and manipulating instruments Stomach muscles are not cut, healing is quicker, less risk of infection Laproscopic Surgery GASTRITIS – acute or chronic inflammation of the stomach lining GASTROENTERITIS Inflammation of mucous membrane lining of stomach and intestine S/S – diarrhea and vomiting for 24-36 hours Complication = dehydration, may need IV fluids ULCER Sore or lesion that forms in the mucosal lining of the stomach/intestines Cause – H. pylori (bacteria) is primary cause Lifestyle factors that contribute: cigarette smoking, alcohol, stress, certain drugs S/S – burning pain in abdomen Antibiotics , antacids H. Pylori COLITIS (IRRITABLE BOWEL SYNDROME) Large intestine inflamed Cause – unknown, stress seems to make it worse – episodes of constipation or diarrhea S/S APPENDICITIS When appendix becomes inflamed If it ruptures, bacteria from appendix can spread to peritoneal cavity causing PERITONITIS Treatment appendectomy HEPATITIS A (Infectious hepatitis) Spread through contaminated food or H2O HEPATITIS B (Serum Hepatitis) Caused by virus found in blood Transmitted by blood transfusion or being stuck with contaminated needles (drug addicts) Health care workers at risk and should be vaccinated CIRRHOSIS Chronic, progressive disease of liver Normal tissue replaced by fibrous connective tissue 75% caused by excessive alcohol consumption JAUNDICE – yellow color when bile pigment gets in bloodstream COLON CANCER Early detection critical HEMOCCULT – stool slide specimen to look for hidden blood COLONOSCOPY after age 50 Rx – colon resection COLOSTOMY – opening in abdomen, healthy bowel brought to skin after cancer removed, pouch worn to collect waste Cancer of the Ascending colon CONSTIPATION When defecation delayed or feces become dry and hard Rx – diet with cereals, fruits, vegetables, (roughage) or fiber, drinking plenty of fluids, exercise, Vomiting allows stomach to empty harmful or irritating contents Hyperemesis Hyperemesis excessive vomiting and diarrhea can lead to dehydration, may need IV fluids