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The Digestive System By Mr. Danilo Villar Rogayan Jr. Instructor I, Department of Natural Sciences RMTU San Marcelino Introduction • Digestion • Mechanical and chemical breakdown of foods into forms that body cells can absorb • The organs of the digestive system carry out digestion • Two categories • Alimentary canal organs • Accessory organs Characteristics of the Alimentary Canal • Wall of alimentary canal • Mucosa • • • Inner most layer; epithelial tissue Secretes enzymes and mucus into lumen Absorbs nutrients • Submucosa • • Inferior to mucosa; loose connective tissue, blood vessels, glands, and nerves Blood vessels carries away absorbed nutrients • Muscular layer • • Just outside submucosa; layers of smooth muscle Contracts to move materials through the canal Characteristics of the Alimentary Canal (cont.) • Serosa • Double-walled outermost layer: peritoneum • Visceral peritoneum • Innermost wall of serosa • Secretes serous fluid to keep outside of canal moist • Parietal peritoneum • Abdominal lining • Movements • Churning – mixes substances in the canal • Peristalsis – propels substances through the tract Checkpoint! What are the layers of the wall of the alimentary canal and what do they do? ANSWER: The layers are: Mucosa: innermost layer; secretes enzymes and mucus into the canal and absorbs nutrients Submucosa: inferior to the mucosa; carries away absorbed nutrients Muscular layer: just outside the submucosa; contracts to move materials through the canal Serosa: double-walled outer layer; secretes serous fluid to keep outside of canal moist The Mouth • Buccal cavity • Mechanical digestion • Takes in food and reduces its size by chewing • Starts chemical digestion • Saliva contains enzyme amylase, which breaks down carbohydrates The Mouth (cont.) • Cheeks hold food in mouth • Lips – sensory nerve fibers that judge temperature of food • Tongue • Skeletal muscles covered by mucous membrane • Lingual frenulum – holds tongue to floor of mouth • Mixes food, holds food between teeth, contains taste buds • Lingual tonsils – lymphatic tissue destroys bacteria and viruses on back of tongue The Mouth (cont.) • Palate • Roof of mouth • Separates oral cavity from nasal cavity • Uvula – portion of soft palate that hangs down in throat • Lymph tissue • Palatine tonsils (oropharynx) • Pharyngeal tonsils – adenoids (nasopharynx) The Mouth (cont.) • Teeth – decrease size • Salivary glands of food particles • Cells • Incisors – bite off food pieces • Cuspids – tear tough food • Bicuspids and molars – grind food • Serous • Mucous • Glands • Parotid • Submandibular • Sublingual Video Clip: How Does Dental Plaque Form Pharynx • Throat • Functions • Connects nasal cavity with oral cavity for breathing • Pushes food into esophagus • Divisions • Nasopharynx • Behind nasal cavity • Oropharynx • Behind oral cavity • Laryngopharynx • Behind larynx • Continues as esophagus Pharynx (cont.) • Swallowing – automatic process 1. Soft palate raises, uvula covers opening between nasal and oral cavity 2. Epiglottis covers larynx, keeping food out of it 3. Tongue presses against roof of mouth, forcing food into oropharynx Pharynx (cont.) 4. Muscles in pharynx contract, moving food toward esophagus 5. Esophagus opens 6. Food is pushed into esophagus by muscles of pharynx The Esophagus • Muscular tube connecting pharynx to stomach • Esophageal hiatus – hole in diaphragm through which esophagus passes • Cardiac sphincter • Circular band of muscle at the opening of the stomach • controls movement of food into stomach Video Clip: Why do we brush our teeth? The Stomach • Below the diaphragm in the upper left quadrant of the abdominal cavity • Functions • Receive food from esophagus • Mix bolus with gastric juice • Start protein digestion • Move food into small intestine • Sections • • • • Cardiac region Fundus Body Pylorus • Pyloric sphincter • Controls movement of substances into small intestine The Stomach (cont.) • Lining of stomach • Rugae – folds of the inner lining • Gastric glands • Mucous cells – secrete mucus to protect the lining • Chief cells – secrete pepsinogen pepsin, which digests protein • Parietal cells • Hydrochloric acid needed to convert pepsinogen to pepsin • Intrinsic factor needed for vitamin B12 absorption The Stomach (cont.) • Gastric glands stimulated by • Parasympathetic nervous system • Gastrin (hormone) • Cholesystokinin (hormone) secreted by the small intestine inhibits gastric glands • Stomach absorbs alcohol, water, and some fatsoluble drugs • Chyme – mixture of food and gastric juices Checkpoint! What are the functions of the stomach? ANSWER: The stomach’s functions are to receive the bolus of food, mix it with gastric juice, start protein digestion, and move food into the small intestine. It also absorbs alcohol, water, and some drugs. Video Clip: How Digestion Works The Small Intestine • Tubular organ extending from the stomach to the large intestine • Duodenum • C-shaped • Short • Jejunum • Functions • Digestion • Absorption of nutrients • Coiled • Majority of small intestine Small Intestine The Small Intestine • Ileum • Attached to large intestine • Mesentery • Fan-like tissue that holds jejunum and ileum in the abdominal cavity • Attaches to the posterior wall of the abdomen • Ileocecal sphincter • Controls movement of chyme from the ileum to the cecum of the large intestine Small Intestine The Small Intestine (cont.) • Lining of small intestine • Microvilli – increase surface area • Intestinal glands • Mucus and water • Enzymes • Peptidases – digest proteins • Sucrase, maltase, and lactase – digest sugars • Intestinal lipase – digests fats • Primary controls • Parasympathetic nervous system • Stretching of intestinal wall Checkpoint! Your patient states that she is lactose intolerant. What does that mean? ANSWER: She cannot produce lactase and cannot digest lactose, which is the sugar in dairy products. The Large Intestine • Extends from the ileum to the anus • Cecum • Beginning of large intestine • Veriform appendix • Ascending colon • Portion that goes up the right side of the abdominal cavity The Large Intestine (cont.) • Transverse colon • Crosses abdominal cavity from right to left • Descending colon • Down left side of abdominal cavity • Sigmoid colon • S-shaped portion in pelvic cavity • Absorbs water and electrolytes Large Intestine The Rectum and Anal Canal • Rectum – off sigmoid colon • Anal canal • Last few centimeters of rectum • Opening to outside of body is the anus Large Intestine The Rectum and Anal Canal • Feces • Leftover chyme • Consists of undigested solid materials, little water, ions, mucus, cells of intestinal lining, and bacteria • Defecation reflex • Triggered by periodic contractions of large intestine • Allows anal sphincters to relax Video Clip: What Causes Constipation The Liver • Lobular organ in right upper quadrant • Large right lobe and smaller left lobe • Hepatic lobules – contain macrophages • Hepatocytes – process nutrients in blood and make bile • Part of liver’s function • Store vitamins and iron The Liver (cont.) • Hepatic portal vein – carries blood from digestive organs to hepatic lobules • Hepatic duct – bile from liver • Hepatic duct merges with cystic duct from gallbladder and forms common bile duct • Common bile duct – delivers bile to duodenum The Gallbladder • Small sac-like structure located beneath the liver • Only function is to store bile • Cholecystokinin causes the gallbladder to release bile Gallbladder Chekpoint! What is the route of bile through the liver and gall bladder? ANSWER: Bile is made in the hepatocytes and leaves the liver through the hepatic duct. The hepatic duct merges with the cystic duct from the gall bladder to form the common bile duct, which delivers bile to the duodenum. The Pancreas Located behind the stomach Acinar cells produce pancreatic juice, which contains these enzymes: Nucleases – digests Pancreatic amylase nucleic acids – digests Trypsin, chymotrypsin, carbohydrates and carboxypeptidase – digest proteins Pancreatic lipase – digests lipids The Pancreas (cont.) • Also secretes bicarbonate ions into duodenum • Neutralize acidic chyme • Enzyme release stimulated by • Parasympathetic nervous system • Hormones secretin and cholecystokinin (from small intestine) Checkpoint! What are the pancreatic enzymes and what do they do? ANSWER: They are: Pancreatic amylase – digests carbohydrates Pancreatic lipase – digests lipids Nucleases – digest nucleic acids Trypsin, chymotrypsin, and carboxypeptidase – digest proteins The Absorption of Nutrients • Nutrients are necessary food substances • • • • • • Carbohydrates Proteins Lipids Vitamins Minerals Water The Absorption of Nutrients (cont.) • Carbohydrates – provide energy • Polysaccharides – starches • Monosaccharides and disaccharides – simple sugars • Cellulose – provides fiber or bulk • Lipids – used for energy when glucose levels are low • Triglycerides • Cholesterol – essential for cell growth and function The Absorption of Nutrients (cont.) • Protein – used for growth and repair of tissue • Essential amino acids body can not make • Vitamins • Fat-soluble • Water-soluble • Minerals – used to make enzymes, cell membranes, and proteins Vitamins • Vitamins are organic molecules required in the diet in small amounts • 13 vitamins essential to humans have been identified • Vitamins are grouped into two categories • Fat-soluble (A, D, E, and K) • Water-soluble • Minerals - are simple inorganic nutrients usually required in small amounts Vitamins • Vitamin A (Retinol) • Lack: Night-blindness, Hyperkeratosis, and Keratomalacia • Overdose: Hypervitaminosis A • Liver, orange, ripe yellow fruits, leafy vegetables, carrots, pumpkin, squash, spinach, fish, soy milk, milk Vitamins • Vitamin B1 (Thiamine) • Lack: Beriberi, Wernicke-Korsakoff syndrome • Over: Drowsiness or muscle relaxation with large doses • Pork, oatmeal, brown rice, vegetables, potatoes, liver, eggs Vitamins • Vitamin B2 (Riboflavin) • Lack: Ariboflavinosis,Glossitis, Angular stomatitis • Dairy products, bananas, popcorn, green beans, asparagus Vitamins • Vitamin B3 (Niacin) • Lack: Pellagra • Over: Liver damage • Meat, fish, eggs, many vegetables, mushrooms, tree nuts Vitamins • Vitamin B5 (Pantothenic acid) • Lack: Paresthesia • Over: Diarrhea; possibly nausea and heartburn • Meat, broccoli, avocados Vitamins • Vitamin B6 (Pyridoxine) • Lack: Anemia; peripheral neuropathy • Over: Impairment of proprioception, nerve damage • Meat, vegetables, tree nuts, bananas Vitamins • Vitamin B7 (Biotin) • Lack: Dermatitis, enteritis • Over: raw egg yolk, liver, peanuts, leafy green vegetables Vitamins • Vitamin B9 (Folic acid) • Lack: Megaloblastic anemiaand Deficiency during pregnancy is associated with birth defects, such as neural tube defects • Over: May mask symptoms of vitamin B12 deficiency • Leafy vegetables, pasta, bread, cereal, liver Vitamins • Vitamin B12 (Cyanocobalamin) • Lack: Megaloblastic anemia • Over: Acne-like rash • Meat and other animal products Vitamins • Vitamin C (Ascorbic acid) • Lack: Scurvy • Over: Vitamin C megadosage • Many fruits and vegetables, liver Vitamins • Vitamin D (Calciferol) • Lack: Rickets and Osteomalacia • Over: Hypervitaminosis D • Fish, eggs, liver, mushrooms Vitamins • Vitamin D (Calciferol) • Lack: Rickets and Osteomalacia • Over: Hypervitaminosis D • Fish, eggs, liver, mushrooms Vitamins • Vitamin E (Tocopherol) • Lack: Deficiency is very rare;sterility in males and abortions in females, mild hemolytic anemia in newborn infants • Over: Increased congestive heart failure • Many fruits and vegetables, nuts and seeds Vitamins • Vitamin K (phylloquinone) • Lack: Bleeding diathesis • Over: Increases coagulation in patients taking warfarin • Leafy green vegetables such as spinach, egg yolks, liver Video Clip: The 5 Fabulous Food Groups Aging and the Digestive System • Decreased motility – GERD • Decreased ability to detoxify blood • Decreased absorption • Sense of taste altered • More likely to develop ulcers and cancers • Dietary changes due to • Isolation • Depression Common Diseases and Disorders Disease / Disorder Description Appendicitis Inflammation of the appendix; can be lifethreatening if not treated promptly Cirrhosis Chronic liver disease; normal tissue is replaced with nonfunctional scar tissue Colitis Inflammation of the large intestine; can be acute or chronic Colorectal cancer Arises from lining of rectum or colon; curable if treated early Common Diseases and Disorders (cont.) Disease / Disorder Description Constipation Difficult defecation Crohn’s disease Inflammatory bowel disease; typically effects small intestine Diarrhea Watery and frequent feces; usually selflimiting Diverticulosis Abnormal pouches in the intestinal wall; no inflammation present Common Diseases and Disorders (cont.) Disease / Disorder Description Diverticulitis Inflammation of diverticuli (abnormal pouches in intestinal wall) of the intestine Gastritis Inflammation of the stomach lining; “upset stomach” Heartburn Gastroesophageal reflux disease (GERD); stomach acids push into esophagus Hemorrhoids Varicose veins of rectum or anus Hepatitis Inflammation of the liver; various types Common Diseases and Disorders (cont.) Disease / Disorder Description Hiatal hernia Portion of stomach protrudes into the chest through an opening (usually the esophageal hiatus) in the diaphragm Inguinal hernia Portion of large intestine protrudes in the inguinal canal (where thigh and trunk meet) or, in males, into the scrotum Usually involves the lips or tongue but can occur anywhere in the mouth; tends to spread rapidly Oral cancer Common Diseases and Disorders (cont.) Disease / Disorder Description Pancreatic cancer Fourth leading cause of cancer deaths in the U.S. Stomach cancer Commonly in cardiac portion of the stomach; occurs more frequently in Japan, Chili, and Iceland Stomach ulcers Breakdown in lining of the stomach; can be caused by bacteria (H. pylori) or smoking, alcohol, excessive aspirin use, and hypersecretion of stomach acid In Summary • Purpose of the digestive system is to provide nutrients to the body • Organs of alimentary canal are responsible for mechanical and chemical breakdown of food • Accessory organs • Assist in breakdown of food • Eliminate waste • Medical assistant must have knowledge of this system • Assist with procedures • Patient education Take all that is given whether wealth, love or language; nothing comes by mistake and with good digestion all can be turned to health. ~ George Herbert