NHM 101 1nd Edition Lecture 8 Outline of Last Lecture I Secretions of digestion Outline of Current Lecture II Definitions III Anatomy of Digestive Tract IV Sphincter V Digestion VI Absorption VII Transport Current Lecture Digestion the process by which food is broken down Absorption the uptake of nutrients by the cells of the small intestine for transport into either the blood or lymph system Gastrointestinal GI tract the digestive tract Flexible muscular tube that extends from the mouth to the anus Lumen the inner space within the GI tract and is continuous from one end to the other Anatomy of Digestive Tract Mouth o The process of digestion begins in the mouth Chewing and crushing food pieces Fluids from food beverages and from salivary glands blend with food for easy swallowing o Food is swallowed passed through pharynx short tube shared by both digestive and respiratory system epiglottis closes off the airway food enters the esophagus as the upper esophageal sphincter opens o Carbohydrate digestion begins here Esophagus o Upper esophageal sphincter opens and food enters into the esophagus Sphincter muscle at each end of esophagus These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute o Food moves through the esophagus and passes through a hole in the diaphragm o Lower esophageal sphincter opens to allow food into the stomach Stomach o Food particles enter stomach upon the opening of the lower esophageal sphincter o Food slowly transfers from the from the upper portion of the stomach to the lower portion At the same time juices are added to the food and ground into a semiliquid mass called chyme o Chyme is released as the pyloric sphincter opens and goes into the small intestine o Strongest Muscle of GI Tract o Thickest walls o Stomach wall releases gastric juices until chyme is liquefied o Pyloric sphincter opens about three times per minute to allow chyme food contents into small intestine o Digestion of Carbohydrates continue in the stomach and the digestion of protein and fat begin in the stomach Small Intestine o 10 ft of tubing o Chyme enters into the small intestine as the pyloric sphincter opens The pyloric sphincter only allows a small amount of food at one time to pass by o Chyme bypasses the opening on the common bile duct which drips fluid The fluid is from the gallbladder and the pancreas o Chyme travels through three segments Duodenum Jejunum Ileum o Most digestion occurs in the Small Intestine Large Intestine Colon o Remaining contents enter the large intestine through the ileocecal valve o Large intestine withdraws water as intestinal contents pass to rectum Leaves a semisolid waste o Rectum and anal muscles hold back waste until rectal muscles relax and two anal sphincters open Rectum Anus What is a Sphincter Circular muscle surrounding and able to close a body opening Keeps the flow of food in one direction There are multiple throughout the GI tract that regulate the flow of food particles o Upper esophageal sphincter mouth pharynx to esophagus o Lower esophageal sphincter esophagus to stomach o Pyloric sphincter stomach to small intestine o Ileocecal valve small intestine to large intestine o Two sphincters of the anus How does food move through the Gastrointestinal Tract Peristalsis wavelike muscular contractions of the GI tract that push the contents o https www youtube com watch v Ujr0UAbyPS4 o Peristalsis occurs continuously GI tract is ringed with circular muscles and surrounding the rings are longitudinal muscles o Circular muscles tighten and long muscles relax tube is constricted o Circular muscles relax and long muscles tighten tube bulges Sphincter muscles open and close periodically Absorption Most absorption occurs is the Small Intestine Fibers are not absorbed and continue through the digestive tract o Carry some minerals bile additives and contaminants out of the body o Helps exercise the GI muscles and keeps them strong to perform peristalsis Intestinal bacteria ferment some fibers producing water gas and small fragments of fat in the large intestine Large intestine retrieves material that it can use o Water and dissolved salts Blood continuously comes by the surface of the Small Intestine an carries nutrients away Nutrient molecules are trapped in microvilli tiny fingerlike projections on each cell villi Nutrient molecules are digested further by enzymes on the microvilli and then absorbed into the cell Absorption typically occurs by diffusion Nutrient molecule crosses the cell of a vilus diffusion Then enter either the vascular system bloodstream or the lymphatic system Bloodstream o Water soluble vitamins and smaller products of fat digestion o Then go to the liver Lymphatic System o Fat soluble vitamins and larger fats o Due to being insoluble in water and the bloodstream is primarily water o Initially bypass liver Bloodstream Arteries carry blood from the heart to the digestive system Hepatic portal vein carries blood away from the digestive system o Blood goes to liver Hepatic vein carries blood from the liver to the heart Liver is the first organ to receive nutrients digested in the GI tract A Healthy Gastrointestinal Tract GI bacteria o 10 trillion o Prevalence of bacteria depends on pH peristalsis diet etc o Primarily beneficial bacteria flora Beneficial bacteria o Probiotics bacteria found in foods and supplements that are beneficial to health Alleviate diarrhea constipation IBS ulcers allergies o Prebiotics food for probiotics