Nutrition 101 Chapter 3 Notes
Nutrition 101 Chapter 3 Notes Nutrition 101
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This 5 page Class Notes was uploaded by Rachel Counce on Thursday March 5, 2015. The Class Notes belongs to Nutrition 101 at University of Alabama - Tuscaloosa taught by Lori Greene in Spring2015. Since its upload, it has received 33 views.
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Date Created: 03/05/15
Rachel Counce Exam 1 Nutrition Chapter 3 Digestion Absorption and Transport Definitions 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 the lymph system Gastrointestinal GI Tract the digestive tract 0 A exible 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 39 Anatomy of the Digestive Tract Mouth Esophagus Stomach Small Intestine 39 Large Intestine colon Rectum Anus Mouth The process of digestion begins in the mouth 0 Chewing and crushing food pieces 0 Fluids from food beverages and from salivary glands blend with food for easy swallowing 0 Taste buds detect sweet sour bitter salty four basic taste sensations and umami savory avor Food is swallowed 9 passes through the pharynx short tube shared by both the digestive and respiratory system 9 epiglottis closes off the airway 9 food enters the esophagus as the upper esophageal sphincter opens 39 Carbohydrate digestion begins here What is a Sphincter A circular muscular surrounding and able to close a body opening 0 Keeps the ow of food in one direction 0 There are multiple throughout the GI tract that regulate the ow of food particles Upper esophageal sphincter mouthpharynx to esophagus Lower esophageal sphincter esophagus to stomach Rachel Counce Exam 1 Pyloric sphincter stomach to small intestine Lleocecal valve small intestine to large intestine Two sphincters of the anus Esophagus Upper esophageal sphincter opens and food enters into the esophagus Sphincter muscle at each end of the esophagus Food moves through the esophagus and passes through a hole in the diaphragm Lower esophageal sphincter opens to allow food into the stomach Stomach Food particles enter stomach upon the opening of the lower esophageal sphincter 0 Food slowly transfers from the upper portion of the stomach to the lower portion 0 At the same time juices are added to the food and ground into a semi liquid mass called chyme Chyme is released as the pyloric sphincter opens and goes into the small intestine Strongest muscles of the GI tract Thickest walls Stomach wall releases gastric juices until chyme is liquefied Pyloric sphincter opens about 3 times per minute to allow chyme food contents into the small intestine Digestion of carbohydrates continue in the stomach and the digestion of protein and fat begin in the stomach Small Intestine 10 feet of tubing 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 Chyme bypasses the common opening of the bile duct which drips uid The uid is from the gallbladder and the pancreas Chyme travels through three segments 0 Duodenum o Iejunum o Ileum Most digestion occurs in the small intestine Large Intestine Colon Remaining contents enter the large intestine through the ileocecal valve Large intestine withdraws water as intestinal contents pass to the rectum Rachel Counce Leaves a semisolid waste Rectum and anal muscles hold back waste until rectal muscles relax and 2 anal sphincters open How Does Food Move Through the GI Tract contents 0 Peristalsis occurs continuously GI tract is ringed with circular muscles and surrounding the rings are longitudinal muscles Peristalsis wavelike muscular contractions of the GI tract that push the Exam 1 0 Circular muscles tighten and long muscles relax tube is constricted 0 Circular muscles relax and long muscles tighten tube bulges o Stomach has third layer of diagonal muscles Sphincter muscles open and close periodically Segmentation a periodic squeezing or portioning of the intestine at intervals along its length by its circular muscles Re ux a backward ow Ex acid re ux from spicy foods Secretions of Digestion Secretions of digestion are required from 5 different organs 0 Salivary glands o Stomach o Pancreas o Gallbladder 0 Small Intestine Secretions bring in an abundance of water and a variety of enzymes Enzymes are proteins that facilitate a chemical reaction Identified by the organ they come from and the nutrient breakdown ex gastric lipase Enzymes in digestion facilitate hydrolysis o Hydrolysis the addition of water to break a molecule into smaller pieces Salivary Glands Squirt just enough saliva to moisten food 0 Saliva contains water salts mucus and enzymes Initiates carbohydrate digestion pll of common substances Basic A pH neutral v Acidic Saliva protects teeth lining of mouth esophagus and stomach from substances that might cause damage Stomach Gastric juices Gastric glands secrete gastric juice 0 Gastric juices contain water enzymes and hydrochloric acid 1 4 1 LA I 0 r0 Coacom39alod lyo Oven cleaner Household ammonia Beng soda O39ange jolce Vinegar Lemon juice m Battery acid Hquot Rachel Counce Exam 1 Stomach contents are highly acidic pH of 2 o Stomach wall protects itself from the acidic juices by secreting mucus Small Intestine Pancreatic juice ex pancreatic lipase enters into the digestive process in the duodenum o Pancreatic juice contains enzymes that act on all 3 macronutrients o It contains sodium bicarbonate which helps to neutralize the chyme that has entered from the stomach Chyme remains neutral or slightly basic from this point forward Bile also enters into the digestive process in the duodenum Liver continuously produces bile and it is stored in the gallbladder o Bile is an emulsifier not an enzyme Cells of the intestinal wall also have digestive enzymes Absorption Most absorption occurs in the small intestine Fibers are not absorbed and continue through the digestive tract 0 Carry some minerals bile additives and contaminates out of the body 0 Helps exercise GI muscles and keep them strong to perform peristalsis o 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 0 Water and dissolved salts Blood continuously comes by the surface of the small intestine and carries nutrients away Nutrient molecules are trapped in the 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 Carrier loads Carrier loads Outside 39 39 39 nutrient on nutrient on cell 39 39 39 outside of cell outside of cell WWW 000000000000 1 000 0000000000 III oeiiillllllllllllllllflllllllfllllillfl Illlllllflllllllllll llllll llllilllllllll quotmm i membrane 39 a and 0 IO 00 0quot39396quoto 0 aquot CO o 00 1 39V and then and then 39 1 39 releases it on releases it on 39nS39de 39 inside of cell inside of cell cell SIMPLE FACILITATED ACTIVE DIFFUSION DIFFUSION TRANSPORT Some nutrients such as water Some nutrients such as the water soluble Some nutrients such as glucose and and small lipids are absorbed vitamins are absorbed by facilitated diffusion amino acids must be absorbed by simple diffusion They cross They need a specific carrier to transport them actively These nutrients move against into intestinal cells freely from one side of the cell membrane to the a concentration gradient which other Alternatively facilitated diffusion may requires energy occur when the carrier changes the cell membrane in such a way that the nutrients can pass through Rachel Counce Exam 1 Circulatory System and Nutrients Absorption Continued Nutrient molecule crosses the cell of a villus diffusion Then enter either the vascular system bloodstream or the lymphatic system Bloodstream o Watersoluble vitamins and smaller products of fat digestion 0 Then got to the liver Lymphatic system 0 Fatsoluble vitamins and larger fats 0 Due to being insoluble in water and the bloodstream is primarily water 0 Initially bypass liver Bloodstream Artery carries blood from heart to the digestive system 0 Heart to arteries to capillaries to veins to heart Hepatic portal vein carries blood away from the digestive system 0 Blood goes to the liver 0 Simply put heart to arteries to capillaries in intestines to hepatic portal vein to capillaries in liver to hepatic vein in heart Hepatic vein carries blood from the liver to the heart Liver is the first organ to receive nutrients digested in the GI tract and is the most metabolically active 0 Liver defends the body by detoxifying substances 0 Also prepares waste for excretion o All nutrients bypass the liver first before being transported into body s cells A Healthy GI Tract GI bacteria 0 10 trillion Prevalence of bacteria depends on pH peristalsis diet etc Primarily beneficial bacteria ora Beneficial bacteria 0 Probiotics bacteria found in foods and supplements that are beneficial to health 0 Alleviate diarrhea constipation IBS ulcers and allergies o Prebiotics food for probiotics 2 systems coordinate all the digestive and absorption processes endocrine and the nervous system health GI tract needs a balanced diet adequate rest and regular physical activity
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