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Digestive System Digestive System Functions 1. Ingestion-of food through the mouth 2. Mechanical processingtearing, chewing, mixing, churning 3. Digestion-chemical breakdown. Makes small particles that can be absorbed by the digestive epitelium Digestive System Functions 4. Secretion-acids, enzymes, buffers from digestive lining or accessory organs 5. Absorption- nutrients and water go into interstitial fluids of digestive tract. 6. Compaction- undigested matter loses water and, therefore, takes up less space 7. Defecation- excretion Digestive System Digestive System = Digestive Tract Also GI (gastrointestinal) Tract, Alimentary canal Digestive Tract Basically a tube from mouth to anus Lined with mucus membrane (protects against digestive acids and enzymes) Peritoneum—membrane lining abdomino-pelvic cavity Peristalsis-wave like smooth muscle contraction that move things along( liquid and solid) through the digestive tract Segmentation movements- churn and mix digestive contents (as in the stomach) Salivary Glands Oral Cavity Sublingual Submandibular Parotid Gland Tongue Pharynx Epiglottis Esophagus Spleen Liver Duodenum Gallbladder Pancreas Stomach Transverse Colon Descending Colon Ascending Colon Jejunum Appendix Sigmoid Colon ileum Rectum Anus Oral Cavity Functions: Analyzes ingested matter Mechanical processing Lubricates ingested matter Begins digestion of carbohydrates Oral cavity = buccal cavity 1. 2. 3. 4. Cheeks are the lateral walls Labia = lips Gingiva = gums Lingual frenulum attaches tongue to epithelium Oral Cavity (cont.) Uvula Small, soft structure hanging from the soft palate Tongue Functions Mechanical processing Manipulation Sensory analysis Teeth Deciduous teeth-primary teeth/baby teeth- 20 Permanent teeth-secondary- 32 including wisdom teeth Mastication = chewing Bolus-food is chopped and ground and mixed with saliva. Bolus is swallowed Pharynx and Esophagus Pharynx = throat Esophagus Muscular action moves bolus down through pharynx to.. About 1 foot long and ¾ in. diameter Deglutition = swallowing Stomach Functions 1. storage of ingested matter 2. mechanical breakdown 3. chemical breakdown with acids and enzymes Chyme mixture of bolus with gastric juices (acids and enzymes) Stomach (cont.) Pyloric Sphincter- at bottom of the stomach, regulates passage of chyme from stomach to small intestines Gastric juice- made of parietal cells and chief cells in stomach Parietal cells secrete: Intrinsic factor (helps with vit. B12 absorption) Hydrochloric acid (decreases pH, kills organisms, breaks down cell walls and connective tissues in food and activates chief cells Chief cells- secretion result in the production of pepsin which breaks down proteins Gastric Functioning Cephalic phase- vagus nerve stimulated by thought or sight of food leads to increased production of gastric juices Gastric phase- begins when food gets to stomach. Increased production of gastric juices and gastric contractions (segmentation movements) Intestinal phase- food enters small intestine. Gastric activity slows down so small intestine can absorb nutrients effectively Stomach Diseases and Disorders Gastritis- inflammation of gastric mucosa Can be caused by alcohol, aspirin, severe emotional or physical stress, bacterial infection of gastric wall or ingestion of strong acid or alkaline chemical Peptic Ulcer- sore in the stomach linked to too much acid or not enough alkaline mucus. Often caused by bacteria Causes sharp pain, sometime bleeding Treatment: antacids or prescription meds to decrease acid secretions Small Intestine Subdivisions Duodenum- 1 ft., closest to the stomach. Adds buffers to increase pH of chyme entering from the stomach Jejunum- 8 ft., middle part , absorption Ileum- part that joins to large intestines. Absorption is completed. Contains lymphatic nodules Small Intestine (cont.) Vomiting reflex- happens in response to irritation of digestive lining. Soft palate and pharynx are especially easily stimulated by unpleasant stimuli. Vomiting can also be caused by irritation of esophagus, stomach or upper parts of small intestine. Medulla oblongata contains vomiting center emesis = vomiting Gasroenteritis- inflammation of stomach and intestines. Combination of vomiting and diarrhea Large Intestine 2 parts—colon and rectum Also known as the bowel (About 5 feet long) Functions 1. Reabsorb water and compact feces 2. Absorb vitamins freed by bacterial action 3. Store feces before defecation Chyme (food and gastric juices enters the Cecum then to -> Ascending colon then to -> Transverse colon Then to -> Descending colon then to ->Sigmoid colon Large Intestine (continued) Diverticulosis Diverticulitis Pockets of mucosa of colon Inflammation of divericula causing pain and occasionally bleeding Colitis- general term for inflammation of colon Irritable Bowel Syndrome- diarrhea, constipation or alternation between the two Large Intestine (cont.) Inflammatory bowel disease = ulcerative colitis Chronic infection of the digestive tract ( inflamed and ulcerated mucosa) Colectomy – part of the colon removed Colostomy- new opening created for evacuation of feces (also known as ileostomy) 1500 ml chyme enter large intestine each day. 200 ml feces are defecated Feces—75% water, 5% bacteria, 20% undigested matter Rectum Last 6 inches of digestive system 2 sphincters- internal and external Anus-external opening Hemorroids= distended veins of rectum and anus (similar to varicose veins) Rectum (cont) Colo-rectal cancer- high mortality rate Test for diagnosis- check feces for blood Lower GI series (barium enema with x-rays) will show masses Colonoscopy- scope that visualizes and collects tissue samples and can remove polyps Defecation Distention of rectum triggers defecation reflex Diarrhea- lots of watery feces. Feces move through the colon too fast. Cause can be bacterial, viral or protozoal infection or anything irritating to the intestines. Diarrhea removes the irritant, put prolonged diarrhea can lead to dehydration and electrolyte loss Cholera- diarrheal disease caused by bacterial toxin. Can cause loss of 1 liter of fluid per 1 hour Caused by poor santitation Vaccine not effective and short lasting, treat with IV and oral fluids Defecation (cont) Constipation- fecal material moves through the colon too slowly, so too much water is absorbed. Feces become dry, hard, abrasive and difficult to move Cause: too little fluid, too little fiber in diet, too little exercise Treatments: stool softener, laxatives, enemas Accessory Organs Salivary Glands Parotid Sublingual Submandibular Makes 1-1 ½ liters of fluid daily which is >99% water Saliva functions: Lubricates, Dissolves chemicals Stimulates taste buds Salivary Glands Diseases Mumps- virus targets parotid glands First exposure usually give permanent immunity Vaccine In males after adolescene, virus can infect testes and lead to sterility Mumps virus in pancreas can lead to diabetes (temporary or permanent) Liver Hepar, hepat = liver 3 functions 1. metabolic regulation 2. hematologic regulation 3. bile production Liver Diseases and Disorders Hepatitis- there are several types of Hepatitis (A,B,C,D, and E). Caused by a virus. Virus attacks liver cells. Hepatitis A- “infectious hepatitis” from eating contaminated food, water, milk, shellfish Hep B- “serum hepatitis” spread by intimate contact with blood, body fluids. Vaccine Hep C- “chronic hepatitis” spread through blood Liver Diseases and Disorders Hepatitis continued Virus attacks liver cells. The person can get a fever. The liver can become inflamed and tender. Blood contents of liver are affected as well as liver function. Can lead to jaundice. Victims usually recover. Some have no signs or symptoms Liver Diseases and Disorders Cirrhosis- liver cells are destroyed by exposure to alcohol or other drugs, viral or bacterial infection, nutritional deficiency(lack of proteins) or blockage of hepatic ducts. Extensive areas of scar tissue form in liver. Symptoms include jaundice, ascites (too much peritoneal fluid) Gallbladder Stores bile Cholelithiasis –(condition of having gall stones)caused by bile being too concentrated, causing crystals and salts to appear (gallstones) Cholecystitis – inflammation of the gallbladder. Gallstones enter and jam the bile duct or cystic duct. Painful- surgery removes large gallstones. Cholecystectomy – surgical removal of gallbladder Pancreas 2 functions 1. Endocrine Pancreatic islets secrete insulin and glucagon 2. Exocrine Secrete water, ions and digestive enzymes Most of the Pancreatic Enzyme’s work of digestion is in the small intestine. Digestion and Absorption Carbohydrate digestion Begins in mouth Completed in duodenum Flatus (intestinal gas) caused by indigestible carbohydrates) Lactose intolerance- no lactase production. Ones can’t digest milk products. Causes gas, cramps, diarrhea. Has genetic basis. About 15% of Caucasian, 80-90% of AfricanAmericans and Asians Digestion and Absorption Lipid digestion and absorption Begins in the duodenum with the release of bile salts, then moves into lymphatics and blood stream Protein digestion and absorption Mechanical processing begins in the mouth. Actual digestion starts in the stomach with acids and pepsin. Pancreatic enzymes finish digestion, then proteins move into interstitial fluids, then blood stream Digestion and Absorption Water and electrolytes Normal daily fluid intake 2000ml in food and drink Most absorbed in intestines Water soluble vitamins (except B12) Absorbed easily by digestive epithelium. B12 needs intrinsic factor from parietal cells in stomach in order to be absorbed Fat soluble vitamins Contained in fat droplets absorbed with emulsification via duodenum. Vitamin K manufactured by bacterial action and absorbed in colon Aging and the Digestive System Most elders have normal digestion and absorption Common difficulties: Decreased peristalsis which leads to increased constipation Decreased sense of taste Increased likelihood of indigestion Increased likelihood of digestive system cancers Digestive epithelium becomes more fragileincreases likelihood of ulcers In general, the bad habits of a lifetime create these problems- cumulative damage can lead to tooth loss, cirrhosis, diverticulitis…