NHM 101 1nd Edition Lecture 8 Outline of Last Lecture I. Secretions of digestion Outline of Current Lecture II. Definitions III. Anatomy of Digestive TractIV. SphincterV. DigestionVI. AbsorptionVII. TransportCurrent LectureDigestion: 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 swallowingo Food is swallowedpassed through pharynx(short tube shared by both digestiveand 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 esophagusThese 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 diaphragmo Lower esophageal sphincter opens to allow food into the stomach - Stomach:o Food particles enter stomach upon the opening of the lower esophageal sphinctero 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 semi-liquid mass called chymeo Chyme is released as the pyloric sphincter opens and goes into the small intestine o Strongest Muscle of GI Tracto Thickest wallso Stomach wall releases gastric juices until chyme is liquefiedo Pyloric sphincter opens about three times per minute to allow chyme(food contents) into small intestineo Digestion of Carbohydrates continue in the stomach and the digestion of protein and fat begin in the stomach- Small Intestine:o 10 ft. of tubingo 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 byo 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 Ileumo Most digestion occurs in the Small Intestine- Large Intestine (Colon):o Remaining contents enter the large intestine through the ileocecal valveo Large intestine withdraws water as intestinal contents pass to rectum Leaves a semisolid wasteo Rectum and anal muscles hold back waste until rectal muscles relax and two analsphincters open- Rectum- AnusWhat 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 particleso 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 anusHow 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=Ujr0UAbyPS4o Peristalsis occurs continuously - GI tract is ringed with circular muscles and surrounding the rings are longitudinal muscleso Circular muscles tighten and long muscles relax= tube is constrictedo 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 tracto Carry some minerals, bile, additives, and contaminants out of the bodyo 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 useo 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- Bloodstreamo Water-soluble vitamins and smaller products of fat digestiono Then, go to the liver- Lymphatic Systemo Fat-soluble vitamins and larger fatso Due to being insoluble in water and the bloodstream is primarily watero Initially bypass liverBloodstream:- Arteries carry blood from the heart to the digestive system- Hepatic portal vein carries blood away from the digestive systemo 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 bacteriao 10 trilliono Prevalence of bacteria depends on pH, peristalsis, diet, etco Primarily beneficial bacteria (flora)- Beneficial bacteriao Probiotics: bacteria found in foods and supplements that are beneficial to health Alleviate diarrhea, constipation, IBS, ulcers, allergieso Prebiotics: food for