Nutrition Chapter 3 Digestion Processes by which food you eat is broken down into components small enough to be absorbed into the body Absorption The processes of taking substances nutrients from the digestive system into the interior of the body Gastrointestinal Tract Continuous tube from the mouth to the anus Path is mouth pharynx esophagus stomach small intestine large intestine rectum and anus Lumen Inside the tube lined with a layer of mucosal cells Accessory organs Salivary glands liver gall bladder and pancreas Mucus Secreted from mucosal cells lining the digestive tract it moistens lubricates and protects Enzymes Protein molecules that speed up reactions in the digestive tract they help breakdown larger molecules of food into smaller ones Hormones In the digestive tract regulate digestion and rate at which food moves through the GI Mouth mechanical and chemical digestion begins tongue chewing saliva Saliva helps starting the chemical digestion contains the enzyme amylase breaks down starch into shorter sugar chains Pharynx Responsible of swallowing food pass through part of digestive and respiratory system Epiglottis Blocks food from entering the trachea and lungs during swallowing Esophagus Moves bolus of food through a series of coordinated muscle contractions relaxations called peristalsis food passes through a muscular ring called a sphincter at the end of the esophagus to enter the stomach Stomach Temporary storage of food result in chyme very little absorption regulated by signals from the small intestines and is affected by meal size and composition Gastric juice secreted and continues the process of chemical digestion components are water hydrochloric acid pepsinogen mucus Hydrochloric Acid Kills microorganisms inhibits amylase helps digestion of proteins with activation of pepsin and unfolding proteins Mucus in stomach Protects stomach lining from pepsin and hydrochloric acid Small intestine Mechanical digestion through local contractions mixes chyme with digestive juices chemical digestion of carbohydrates proteins lipids and nucleic acids is completed provides primary surface for absorption of nutrients and water Pancreas secretes pancreatic juice containing bicarbonate pancreatic amylase pancreatic proteases pancreatic lipases Intestinal glands secretes intestinal enzymes to aid breakdown of double sugars into simple sugars and break down of short chains of amino acids to single chains of amino acids Liver Produces bile Gallbladder stores bile and secretes bile into small intestine Bicarbonate neutralizes stomach add gastric juices Bile emulsifies far so lipases can access fat molecules Large intestine Ends at the anus absorption of water some vitamins and minerals bacteria intestinal micro flora digest some nutrients and make it vitamin K and some B vitamins rectum stores feces Simple diffusion A substance crosses a cell membrane by moving from a higher concentration to a lower concentration energy not required vitamins and fatty acids Facilitated diffusion A substance crosses a cell membrane with the assistance of a transport protein energy not required fructose Osmosis Water crosses cell membranes freely moves from a lower solute concentration to a high solute concentration till it is the same on both sides energy not required Active transport Energy required Sodium ion glucose amino acids Bloodstream transport pathways Water soluble nutrients and smaller products of fat digestion are absorbed into capillaries liver Lymphatic system transport pathway Larger fats and fat soluble vitamins are absorbed into lacteals Gastro esophageal Reflux heartburn Occurs when stomach content including acids moves from the stomach into the esophagus GERD Chronic heartburn symptoms included burning sensation pain bleeding ulcers and cancer Ulcers Occurs in the esophagus stomach or small intestine from damage to lining by stomach acid and pepsin causes by H Pylori aspirin and other pain relievers symptoms include pain bleeding and cancer Gallstones Solid material accumulates in the gall bladder and or bile ducts and blocks bile symptoms includes pain Diarrhea Frequent watery stools occur when substances move too quickly through the large intestines for water to be absorbed or when water is drawn from cells into the lumen of the intestines caused by infections irritants medications and diseases symptoms include pain dehydration and malnutrition Constipation Hard dry stools which are difficult to pass caused by too little water fiber exercise decreased strength of large intestinal muscles medications