Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
8.3 & 8.4 - Digestive System (Ingestion & Digestion) Adapted by Patrick Shackleford From a presentation by Dr. Jared Heidinger M.D. Ph.D Digestion • The digestive system is interdependent with other body systems to function properly: muscle system, skeletal system, circulatory system, nervous system, endocrine system • How does each help? What we call “Digestion” is actually 4 processes: 1. Ingestion - Taking nutrients into the body (eating) 2. Digestion - Breaking down the organic molecules into smaller complexes – Two types: physical and chemical 3. Absorption - Transport of digested nutrients to the tissues of the body 4. Egestion - Removal of waste and the materials from the food that the body cannot digest The Digestive System 1. Ingestion Mouth to Stomach Mouth Food enters the alimentary canal (digestive tract) through the mouth • the mouth starts the physical digestion by chewing (mastication) with the teeth & tongue • creates bolus (ball of food) Saliva • Contains salivary amylase produced by the salivary glands breaks down starch into simpler carbs (chem. digestion). • Lubricates food for swallowing • Dissolves food in order to be “tasted” Chewing tobacco beautiful images… • In 2006, cigarette companies spent $12.4 billion on advertising and promotional expenses in the United States alone.3 • The money cigarette companies spent on U.S. marketing in 2006 amounted to approximately $34 million per day.3 STATS • Chewing tobacco contains at least 28 known carcinogens. • During 2000–2004, total tobacco use was estimated to be responsible for $193 billion in annual healthrelated economic losses in the United States ( • $96 billion in direct medical costs • $97 billion in lost productivity).10 STATS • The total economic costs (direct medical costs and lost productivity) associated with cigarette smoking are estimated at $10.47 per pack in the United States.11 • In early 2010, the average retail price of a pack of cigarettes in the United States was approximately $4.80. P.S. Chew contains fibreglass. Why? To cut open the flesh to allow nicotine in quicker (strengthen addiction further) From Mouth to Stomach • Pharynx – section where air and food are directed to different tubes • Esophagus – food tube (goes to stomach) • Epiglottis (small cartilaginous flap) flips down and covers the trachea so that no food or drink can go “down the wrong pipe” I am the Master of my body!...well.. • Voluntary control of food only during first phase (ingestion – chewing and swallowing) and last phase (egestion defecation) the rest of the process is involuntary. • Ex. You can’t “try” to move or digest food quicker Esophagus • The esophagus connects the oral cavity to the stomach and uses Peristalsis – a rhythmic, wavelike contraction of the smooth muscle that moves food through the digestive/ G.I tract. G.I. = Gastrointestinal Candida esophagitis (yeast infection) Ulcer in Esophagus Another Ulcer in Esophagus Esophagus to Stomach Sphincters • Regulate the entry and exit of food from the stomach • Act like drawstrings • Lower Esophageal Sphincter (LES)– entry into the stomach – prevents acid reflux • Pyloric Sphincter – regulates move of food out of the stomach into small intestine Stomach • The stomach is the site of food storage and initial protein digestion • Surrounded by 3 layers of muscle (different directions) to churn food into chyme. • J shape & numerous folds allow for 1.5 L capacity • Normal pH ranges from 2.0-3.0 (low as 1.0) Stomach – cells & gastric juices • Up to 500 mL of juices produced after large meal • Mucous cells secrete a protective (alkaline) mucous coating over stomach lining. • Parietal cells secrete HCl (hydrochloric acid) to kill pathogens, denature proteins. • Peptic cells secrete pepsinogen – Pepsinogen changes into the enzyme pepsin in the presence of hydrochloric acid which breaks proteins into smaller polypeptides Gastric Ulcers • Form when the mucous layer breaks down, cells lining the stomach are destroyed by acid & pepsin (stomach literally starts digesting itself) • Steps must be taken to decrease the acidity of the stomach or ulcer will grow (antacids) • Endoscope can be used to view the interior of the body Beautiful isn’t it? ULCERED! The Digestive System 2/3. Digestion & Absorption Small Intestines & Accessory Organs Small Intestine and Pancreas (the digestive duo!) • Small Intestine - small diameter, large in length (up to 7m) 3 Sections 1st – Duodenum – The majority of chemical Digestion occurs here – Bile and Pancreatic ducts connect (add fluids) 2nd – Jejunum 3rd - Ileum Hormones • Part of Endocrine system (bio 30) • Chemicals released by cells that affect cells in other parts of the body (required in small amounts) • Travel through the blood stream • Ex. Secretin (small intestine to pancreas) Digestive Duo cont. Digestive Duo cont. • Pancreatic secretions contain bicarbonate ions HCO3- (basic) • Released into duodenum via pancreatic duct. • Neutralizes low pH of the chyme (contains HCl) raising pH from 2.5 to 9.0 • Pepsin becomes inactive in the high pH, protects duodenum from digestion. If this function of the pancreas is inhibited, a duodenal ulcer can form Pancreatic Secretions: Enzymes • Trypsinogen is released from pancreas, when it enters the small intestine, an enzyme called enterokinase activates the trypsinogen into trypsin which continues digestion on proteins. Pancreatic Enzymes cont. • Lipase – Breaks down fats into component glycerol and fatty acids. • Pancreatic Amylase – Completes the break down of carbs started in the mouth. Small Intestine Secretions • Disaccharidases – Breaks down Disaccharides into monosaccharides. • Ex. Maltase breaks maltose down into glucose. • Erepsin – Completes breakdown of proteins into individual amino acids. Absorption of Nutrients • Stomach absorbs some water, specific vitamins and alcohol • Large Intestine absorbs some vitamins and water • Small Intestine absorbs the most nutrients of all the organs in the digestive system Absorption cont. • Villi - small finger like projections that extend into the small intestine. Villi increase surface area for absorption. Microvilli - infoldings of the cell membrane on the cells. Look like fine hairs covering the cell. The cells that make up the villi in the digestive system also have microvilli on them. Increase S.A. Again! Lacteals • Each villus is supplied with a capillary network that intertwines with lymph vessels called lacteals • Carbohydrates and amino acids are absorbed into capillary network • Fats absorbed into lacteals Liver and Gallbladder • Liver has many functions • Main function related to digestion produces fluid called Bile which contains bile salts - aid in fat digestion by physically emulsifying fat into smaller particles (more S.A. For lipase to chemically digest) • Gallbladder stores and concentrates bile salts when the stomach is empty. Liver and Gallbladder cont. Cholecystokinin (CCK) – hormone released by small intestine in response to fats, stimulates gallbladder to release bile salts. Nice liver man! Liver cont. • Secondary function related to digestion - acts as a storehouse for glycogen and vitamins (A, B12, D) • Also detoxifies the blood (deactivates poisons) the body • alcoholism causes cirrhosis of the liver where the liver becomes inflamed from an increase of non-functioning fibrous tissue and fat. Alcoholic liver Liver and Gallbladder cont. • Crystals of bile salts which form on cholesterol can build up and become a very large mass called a gallstone • Can get stuck in the bile duct when it is on its way to the small intestine (huge amounts of pain) • Can cause Jaundice – Yellow discoloration of skin and eyes due to backup of bile salts in the blood The Digestive System 4. Egestion Large Intestine to Anus Lets take a journey through the colon! Large Intestine - Colon • Chemical digestion of food is complete by the time it reaches the large intestine • Colon - The largest segment of the large intestine • Functions: stores wastes and absorbs water into the body (along with some organic salts) • also houses bacteria which synthesize vitamins B and K Fibre in the colon 1. Fibre is important because it helps to keep water in the large intestine which aids in Egestion (removal) 2. Binds cholesterol, lowers cholesterol levels 3. Adequate fibre intake keeps you “regular” (makes bowel movements regular) which means that toxins are removed from the body on a regular basis. Helps avoid conditions like colon cancer Control of Digestion • Exerted by Nervous and Hormonal systems • Sight, Smell, Taste, Physical, Chemical • Gastrin – secreted by the stomach - stimulates the release of HCl by parietal stomach cells. • Enterogastrone – secreted by small intestine slows peristaltic movements allowing time for fat digestion Control of Digestion GASTRIN ENTEROGASTRONE