Digestive System

1. Digestive System Chapter 17

2. Functions of Digestive System • Ingestion • Secretion • Movement • Digestion • Absorption • Excretion

3. Digestion Types:Mechanical or Chemical Mechanical – muscular actions or movement to tear, grind and mix Chemical – enzymes used to breakdown nutrients.

4. Tissue Layers 1.Serosa:Visceral Peritoneum 2.Muscularis: smooth muscle, circular and longitudinal layers 3.Submucosa 4.Mucosa:epithelial (strat.simple or simple columnar) and areolar tissue

5. Specialized Tissues… • Peritoneum – lines cavity wall (parietal) and covers abdominal organs (visceral). - Retroperitoneal: positional term for behind peritoneum. • Mesentary – thick peritoneal sheets that suspend digestive tract, stabilizing organs, prevents intestine tangling. • Greater Omentum “Fatty apron”– Large folded tissue containing adipose and lymph nodes. Protects, insulates and provides energy reserve.

6. What organs compose theDigestive Tract or Gastrointestinal Tract? What is the direction of transport through the tube from start to finish? What structures are help with digestion but are not part of the GI Tract? Which regions do mechanical and/or chemical digestion?

7. The Oral Cavity • Sensory analysis of material. • Mechanical digestion by teeth and tongue. • Chemical digestion by enzymes. • Lubrication by mucus and saliva • Bolus is formed at end. • 32 adult teeth, 20 deciduous Halitosis – Bad breath

8. Salivary Glands • Types: Parotid, submandibular, and sublignual. • Function: Releases enzymes to digest carbohydrates (starches) into tri-& disarccharides with Salivary amylase. • Small amount of Lingual Lipase starts fat breakdown. • “Mumps”- virus attacks usually parotid glands

9. Pharynx Uvula • Common passageway for solid food, liquids and air. • Regions: 1. nasopharynx 2. oropharynx 3. layrngopharynx • Uvula – blocks food from going into nasophayrnx Epiglottis flap is pushed down by food to cover tracheal opening

10. Esophageal Cancer Human esophagus – 10 inches long Giraffe esophagus – 6 feet long

11. Esophagus • Muscular tube that moves bolus to the stomach by PERISTALSIS. • Mucus secretions keep tube lubed • “Swallow reflex” controlled by medulla. • HeartburnandGERDcan be problems

13. Hiatal Hernia • Part of the stomach moves up through an opening (hiatus) in the diaphragm. • The presence increases the risk for GERD.

14. Stomach • J-shaped organ • Muscular rugae to churn food. • Sphincter doors at both ends. • Gastric Glands: Mucous (Goblet) cells– secrete mucus Chief cells–secretepepsinogen Parietal cells–secrete HCl andintrinsic factor (helps small intestine to absorb Vitamin B12) • Pepsin = Pepsinogen + HCl *This begins digestion of proteins into polypeptides and smaller peptides.

15. Stomach Continued… • Absorption of nutrients: NONE! Only certain drugs and alcohol can be absorbed here. • Hormones regulating stomach: Gastrin – increases gastric secretion Cholecystokinin(CCK) and Gastric Inhibitory Peptide (GIP) - slows gastric motility and secretions Secretin – inhibits gastric secretions Animation • Bolus is turned into CHYMEbefore leaving Carbs pass through quickest and lipids take the longest due to CCK release.

17. Peptic Ulcers *Erosion of the digestive tract layers. Can affect any part of tract. Causes: “Helicobacter pylori” Bacteria (80%), stress, cancers, other disorders

18. Gastric Bypass Surgery • Restricts appetite • Restricts stomach size significantly • Limits absorption of nutrients, fat, and calories. • Allows patients to achieve rapid loss. • Side effects: nausea, weakness, sweating, faintness, and, occasionally, diarrhea after eating, anemia, calcium absorption, and gallstones.

19. Lap Band Procedure A ‘gastric band’ with a small balloon inside is attached around the top portion of your stomach, forming a smaller ‘gastric pouch’. The placement of the band creates a small pouch at the top of the stomach that holds up to approximately 30 ml, which works out to about 1/8 cup. You are inclined to eat less because the pouch holds less food than the whole stomach. As the upper part of the stomach registers itself as being full, it sends a message to the brain saying that the entire stomach is full.

20. Small Intestine • Function: digestion and absorption (90%) • 3 sections: duodenum, jejunum, ileum • Mesentary stabilizes/holds intestine, provides access for blood vessels. • Intestinal villi – fingerlike projections, absorbs nutrients; increases surface area. (There are microvilli on the villi too!) • Ileocecal valve – sphincter muscle; door to cecum of large intestine. • Peristalsis moves chyme through tube. • Bicarbonate ions (from pancreas) increase pH of chyme released at duodenum.

24. Small Intestine • Intestinal enzymes: (peptidase, sucrase, maltase, lactase, lipase, enterokinase) • Lacteals: structures within villi that take in fat/protein complexes; connects with lymphatic system. • Chylomicrons: fatty/protein structures formed by intestinal cells. Video 3 Video Video 2

25. Small Intestine Disorders Celiac Disease: Autoimmune, body attacks villi of small intestine. Can be environmentally triggered. • Inguinal Hernia: protruding through a weak point or tear in the thin muscular abdominal wall. • Can restrict blood supply to the bowel herniated through the defect, creating a medical emergency. Gangrene! • Causes: for adults - heavy lifting, straining bowel movements, coughing.

27. Pancreas • Exocrine function: chemical digestion • Released into the duodenum via pancreatic duct that connects with common bile duct. • Enzymes: amylase, lipase, nuclease, trypsin, chymotrypsin, carboxypeptidase. • Trypsin = trypsinogen + enterokinase • Secretes Bicarbonate ions to increase pH of chyme. • Hormone Regulation: (secreted by small intestine) 1. Secretin- increase pancreatic secretion 2. Cholecystokinin (CCK)- slows down stomach release of chyme, stimulates pancreatic secretion

28. Pancreatitits: inflammation of pancreas; blockage of duct leads to enzymes destroying pancreas.

29. Nutrients are broken down into basic units for absorption

30. LIVER

31. Liver • Bi-lobed, reddish brown organ • All blood from digestive organs stops here first. • Functions: 1. Carbohydrate, protein, and lipid metabolism 2. Detoxification of blood 3. Removes damaged/old blood cells 4. Produces bile 5. Stores vitamins, minerals and glycogen. 6. Participates in formation of vitamin D. • Falsiform Ligament – holds liver to anterior wall • Regeneration capabilities • Hepatocytes – liver cells

32. Liver • Kupffer cells - phagocytize pathogens and old RBC’s • Blood from the hepatic artery and hepatic portal vein carry blood into the liver to be serviced. • Serviced blood leaving the liver exits the hepatic vein which connects with inferior Vena Cava. • Hepatitis – Inflammation of the liver, causes can be viral or chemical.

34. Gall Bladder Fat droplet Bile • Green muscular sac; 10cm • Ventral surface of liver • Stores bile made from liver. • Bile consists of: cholesterol, salts, bilirubin, & other lipids. • Bileemulsifies fats (breaks down into smaller droplets), helping digestion & absorption of fat-soluble molecules. • Released into Cystic duct and travels tobile duct. Fat droplets coated with bile Micelles formed: fatty acids, monoglycerides and bile Absorption of lipid material into villus and chylomicrons formed, moving into the lacteal.

35. Gall Stones Formed from the crystallization of bile salts or cholesterol in the gall bladder. Blockage of cystic duct…PAINFUL! Removal of gall bladder or other ways to break up crystals is the treatment. Diet will have to be careful with fat and cholesterol intake.

38. Large Intestine • Functions: Reabsorbs water; absorbs certain vitamins and electrolytes; forms semi-solid feces; stores feces • Suspended inside cavity by peritoneum but rectum is retroperitoneal. • Sections: a. Cecum: pouch-like part; appendix is posterior end b. Colon: ascending, transverse, descending, sigmoid c. Rectum: anal canal and anus located at end • Ecoli bacteria break down cellulose, make vitamin K, vitamin B5, and GAS! Break down bilirubin giving fecal colors. • No villi but tons of goblet cells for lubrication. • Colon pouches are called “Haustrum” or haustra.

40. Large Intestine…Defecation! • Distension of rectal wall triggers defecation reflex. • Internal anal sphincter (involuntary control) Relaxes on stool entrance • External anal sphincter (voluntary control) Relaxation results in defecation • Hemorrhoids: distended, swollen veins in anal canal

41. Bowel Issues • Diarrhea: not enough water absorbed, food is hurried through. Causes: microbes, stress, food intolerances Problems: dehydration and malnutrition • Constipation: feces remain too long in tract, drying too much. Causes: lack of fiber, dehydration, stress, failure to relieve Problems: Hemorrhoids, hernias, diverticulitis

42. Colitis – inflammation of the colon Diverticulosis – formation of colon pouches, weakening of wall Polyps – bumps on colon wall, precancerous

43. Colon Cancer • 3rd leading cause of cancer related deaths • Standard screening: stool checks and colonoscopy

44. Digestion Animation Quizzes and more! And more! More studying