Digestive System

1. Digestive System Chapter 23

2. QUIZ PICTURE

3. Absorption of Nutrients • The passage of digested molecules of food, water, minerals, and vitamins from the lumen of the GI tract into the mucosal cells by active or passive transport into blood or lymph

6. Upper esophageal Tonic contractions are shown by sphincters; most are smooth muscle, some are skeletal. Lower esophageal Pyloric Oddi Ileocecal Internal anal Fig. 22-9, pg: 691 External anal

7. Quiz Picture

10. Homeostatic Imbalance Peritonitis • Inflammation of peritoneum • Puncture wound of abdomen

11. Salivary Glands • Parotid Glands- located anterior to ear • Sublingual Glands- located in floor of mouth • Submandibular Glands- located under jaw • Function: produce saliva- mostly water, salivary amylase, antimicrobials Saliva moistens food, starts starch breakdown, dissolves food chemicals for taste

13. Homeostatic Imbalance Mumps • Inflammation of parotid gland • Passed by saliva • In males can lead to testes infection

14. Homeostatic Imbalance Halitosis • Inhibited saliva production • No saliva=no washing of mouth • Cavities, anaerobic bacteria make hydrgen sulfide, methyl mercaptan and cadaverine which smell like rotten eggs, feces and corpes

15. Mouth, Pharynx, Esophagus • Mouth- place where mechanical breakdown of food begins with chewing • Pharynx- has 2 skeletal muscle layers whose contractions propel food into esophagus • Esophagus- long tube to stomach posterior to trachea; conduit for food; peristalsis (alternate waves of contraction/relaxation of muscle that propels food to stomach)

17. Swallowing uses contraction of tongue, upper pharynx constrictors, and laryngeal muscles. Is voluntarily initiated, but medullary swallowing center coordinates muscles. Fig. 22-10, pg: 692

18. Stomach • Chemical breakdown of proteins begins here • food becomes chyme • upper end to esophagus is cardiac portion; fundus is top • middle is body and end is pylorus

19. Quiz Picture

20. Stomach Histology Epithelium- simple columnar • Gastric pits- primarily goblet cells • Gastric glands- below gastric pits Neck Cells- produce acidic mucous Parietal Cells- secrete HCl and Intrinsic Factor Chief Cells- produce pepsinogen to digest protein Enteroendocrine Cells- release hormones; gastrin, histamine, endorphins, serotonin, cholecystekinin, somatostatin

23. Stomach Mucosal Barrier • Bicarbonate rich mucous on stomach wall • Epithelial cells connected by tight junctions • Gastric Gland cells impermeable to HCl • Damaged epithelial cells replaced quickly; lining shed every 3-6 days

24. Functions of Stomach • Protein digestion- only enzymatic type that occurs here • Secretion of IF- essential for intestinal absorption of B12; B12 deficiency causes Pernicious Anemia

25. Control of Gastric Secretion • Neural Control-CN X (Vagus)-stimulation causes increase of all gland secretion • Gut Brain local reflexes Hormonal Control-Gastrin- stimulates secretion of enzymes and HCl and hormones of small intestine

26. Homeostatic Imbalances Gastroesophageal reflux disease (GERD) • Heartburn • Stomach acid travels back up esophagus • Hiatal hernia • Damage to esophagus if prolonged

27. Homeostatic Imbalances Gastric Ulcers • Erosion of stomach wall • Breach mucosal barrier • Stress, medicines, bacteria (helicobacter pylori

30. Small Intestine Three Sections 1. Duodenum 2. Jejunem 3. Ilium

31. Peritoneum • Serous membrane- double membrane • Mesentery is a sheet of 2 serous membranes fused back to back; holds part of the GI tract together; extends from body wall to digestive organs; provides route for blood/lymphatic vessels and nerves

34. Quiz Picture

35. Quiz Picture

36. Sm Int

37. 2) villi • fingerlike projections on mucosa • Surface cells for absorption • Contains capillary bed and lacteal (lymph capillary) • Made of cells

38. 3) microvilli • tiny plasma membrane projections of absorptive cells of mucosa • Fuzzy appearance called brush border • Brush border enzymes located here • On a single cell

39. Histology of Small Intestine • Epithelium- simple columnar with goblet cells; enteroendocrine cells that secrete intestinal Gastrin, Secretin, Cholecystikinin (CCK), GIP, VIP • Intestinal Pits located above intestinal glands that are called Crypts of Leiberkuhn- secrete intestinal juice, lysozyme • Brunner’s Glands- duodenum only; alkaline mucous

41. Liver • Digestive function- produce bile for transport to small intestine • Other functions include storage of Vit. A, D, E, and K and production of proteins including albumin, clotting factors and production of cholesterol

42. Gross anatomy of Liver • About 3 pounds • Divided into right and left lobes • Bile produced in the liver leaves through the common hepatic duct which joins the Cystic Duct of the gall bladder to form the Common Bile Duct • Under R costal margin from 5th to 10th rib

44. Histology of Liver • Functional Unit- Liver Lobule consisting of hepatocytes (liver cells) and vessels; hexagonal with each corner being a portal triad (artery, vein, bile duct); center is the central vein • Sinusoids- leaky capillaries between liver cells; also Kupffer cells (macrophages • Bile Canaliculi- canals between liver cells that take bile to bile ducts

47. Homeostatic Imbalances Cirrhosis • Chronic inflammation of the liver • Obstructed blood flow through liver, portal hypertension • Chronic alcoholism or hepatitis

48. Bile • Bile Salts- cholesterol derivatives; emulsify fats • Phospholipids • Fats • Electrolytes • Bile Pigments