Understanding the Digestive System: Part 1

1. Ch. 23 The Digestive System– Part 1 Part 1: 18 slides (excluding student assignment and photos

2. I. Basic Concepts & Processes Shared By Most Digestive Organs A. Two Groups of Organs: • *Alimentary canal = • *Organs: Students Do • *Accessory digestive organs =

3. B. Digestive Processes Do Basic Definitions for all below: • *Ingestion 2. *Propulsion • *Peristalsis 3. *Mechanical digestion • *Mastication • *Segmentation 4. * Chemical digestion 5. * Absorption 6. *Defecation Ingestion Propulsion Mechanical Digestion Absorption Defacation

4. C. Blood Supply Celiac trunk Branches of Abdominal Aorta Review *Celiac Trunk and 3 branches *Gastric Artery * Splenic Artery * Hepatic Artery *Superior Mesenteric Artery *Inferior Mesenteric Artery Superior mesenteric artery Inferior mesenteric artery

5. Dorsal mesentery Parietal peritoneum Ventral mesentery Visceral peritoneum Peritoneal cavity D. Peritoneum Students Do • *Peritoneum: Visceral and Parietal layers • * Mesentery • * Greater Omentum Alimentary canal organ Liver Figure 23.5a

6. • Epithelium • Lamina propria • Muscularis mucosae Submucosa • Longitudinal muscle • Circular muscle Lumen E. General Histology of Alimentary Canal Mucosa • *Mucosa • Epithelium • Lamina Propria • Muscularis Mucosae • *Submucosa • Areolar • Many blood vessels 3. *Muscularisexterna • Circular (inner) • Longitudinal • Sphincters 4. *Serosa = Visceral Peritoneum Muscularis externa Serosa

7. II. Digestive System Organs of the Head and Thorax: Anatomy & FunctionA. The Mouth & Associated Organs Students Do Following 1. Mouth Anatomy • *Tissue Lining: • *Palate: Hard &Soft • *Uvula: 2. Overall Functions: • Ingestion, Mechanical Digestions • *Chemical digestion: amylase digests what? • Swallowing (Deglutition) READ

8. Lingual Tonsil 2. * The Tongue STUDENTS DO • * Basic Composition: • * Functions: 3 • * Bolus • Lingual Lipase

9. Parotid gland Ducts of sublingual gland Parotid duct Sublingual gland Submandibular duct Submandibular gland 3. * The Salivary Glands Students Do • * 3 pairs of Glands: • * Functions: • * Compositionof Saliva 1. Lubrication 2. hydration of food 3. chemical digestion 4. protection from microbes (clinical medium) Tongue Masseter muscle Body of mandible (cut)

10. B. Pharynx • * Regions: Students Do • Lining: squamous e.t. • skeletal muscle for • * Function: Oropharynx Laryngopharynx

11. C. Esophagus = propulsion only READ & FILL IN • = Muscular Tube • Function: Propulsion/Peristalsis • * Esophageal hiatus • * Upper & Lower Esophageal Sphincters (Lower = Gastroesophageal Sphincter) • Histology: stratified squamous Diaphragm

12. D. Digestive Processes– Mouth to Esophagus: SWALLOWING & Propulsiontowards Stomach READ = Involves coordinated action of tongue, pharyngeal muscles, esophageal muscles (including the sphincters), and layngeal muscles. Bolus of food Tongue Pharynx Epiglottis Glottis Trachea

13. III. Digestive Organs of the Abdomen-PelvisA. The Stomach: 1. *Overall Functionsa) b) c) d) 2. *Gross Anatomy Cardia Fundus Body Serosa Lesser curvature Rugae of mucosa • a) * Regions • Body • Cardia • Pyloric • Fundus • b) *Rugae Greater curvature PyloricRegion Duodenum Pyloric sphincter Figure 23.14a

14. A. The Stomach… 2. Gross Anatomy … Cardia Fundus • c) *Curvatures • Greater • Lesser • d) *Sphincters • Cardiac • Pyloric Serosa Body Lesser curvature Rugae of mucosa Greater curvature PyloricRegion Duodenum (a) Pyloric sphincter Figure 23.14a

15. The Stomach: … Gross Anatomy … Cardia Fundus READ f) Muscular tunic has extra 3rd layer = inner most oblique layer = churning action Serosa Body Lesser curvature Rugae of mucosa Greater curvature Pyloric canal Pyloric antrum Duodenum Pyloric sphincter (valve) at pylorus (a) Figure 23.14a

16. 3.Microscopic Anatomy of the Stomach - Has all Layers

17. Mucous neck cells 3. Microscopic Anatomy of Stomach …a) Mucosa i) *Tissue? Esophagus • ii) *Gastric Pits: lead to the • Gastric Glands which produce • Gastric Juice– with mucus, enzymes (gastrin), and hormones in it • iii) Cells of Gastric Glands • (1) Muscus Neck Cells • Produce Alkaline mucus w/ bicarbonate • Function: protect cells from very low pH (1.5 – 3.5) gastric juice READ Stomach Gastric Pits Gastric Glands Figure 23.12b

18. Gastric pits Surface epithelium (mucous cells) Gastric pit Mucous neck cells Gastric gland Parietal cell Chief cell Enteroendocrine cell iii) Gastric Gland Cells … (2) Parietal Cells • Function: Produces Hydrochloric Acid (HCl) for activation of enzyme pepsinogen AND Produces intrinsic factor for B12 absorption • Slide: Round, large, pinkish cells (3) Chief Cells • Function: produce enzyme Pepsinogen which activates to Pepsin • Slide: Small, purplish cells (4)Enteroendocrine Cells: produce Gastrin HCl Pepsinogen Pepsin (b) Enlarged view of gastric pits and gastric glands

19. STOMACH

20. Stomach

21. 4. Digestive Processes Occurring in the Stomach READ a) Introduction i) Secretions: Up to 3L per day ii) Nervous Control: • Parasympathetic NS via VagusNerve: stimulates glands • Sympathetic NS: decreases secretary action iii) Hormonal Control • Gastrin, most important hormone Stimulates secretion of enzymes, HCl, & intestinal enzymes

22. 4. Digestive Processes occurring in the Stomach … Stimulatoryevents READ Cephalic phase 1 Sight and thought of food Cerebral cortex Conditioned reflex b) Regulation of Gastric Secretion • 3 Phases i) Cephalic (reflex) phase: 2 Stimulation of taste and smell receptors Hypothalamus and medulla oblongata Vagus nerve Are Stimuli • Sight and Thoughts & Tastes and Smells  Hypothalamus Medulla nuclei  Vagus Nerve  Stomach  RESULT = increased secretions • - Takes a few min. Stomach secretory activity Figure 23.17

23. Are Stimuli 2. Regulation of … READ ii) Gastric Phase: Stomach Distention, Food Chemicals (proteins), and increasing HClRESULT = Increased gastric juices AND Release of Gastrin which causes Parietal Cells to Increase HCl secretion • The increase in acidity (low pH) activates pepsinogen to pepsin which catalyzes the break down of proteins • NegatieFeedback Loop: Low H+ (High pH) stimulates release of Gastrin AND High H+ (low pH) inhibits release of Gastrin Stimulatory events Inhibitory events 1 1 Stomach distension activates stretch receptors Excessive acidity (pH <2) in stomach Vagovagal reflexes Medulla Vagus nerve Gastrin secretion declines G cells 1. Excessive acidity (pH <2) in stomach 1 Stomach distension activates stretch receptors Vagovagal reflexes Medulla Vagus nerve Gastrin secretion declines G cells Gastric phase 2 Emotional upset Local reflexes Overrides parasym- pathetic controls Sympathetic nervous system activation Ach Local reflexes Overrides parasym- pathetic controls Sympathetic nervous system activation 2. Emotional upset 2 Food chemicals (especially peptides and caffeine) and rising pH activate chemoreceptors G cells Gastrin release to blood 2 Food chemicals (especially peptides and caffeine) and rising pH activate chemoreceptors G cells Gastrin release to blood Stomach secretory activity Stomach secretory activity Stimulate 1 Entero- gastric reflex Local reflexes Inhibit Figure 23.17 Presence

24. c. Intestinal Phase– in Duodenum READ Stomach secretory activity Stimulatory events • Begins when stomach starts to empty partially digested food (chyme) to duodenum (1) Partially digested food & low pH  release Intestinal Gastrin  RESULT = Stomach glands continue to secrete gastric fluids briefly (2) Distension of Duodenum & very low pHInhibits gastric secretions and closes the Pyloric Sphincter 1 Presence of low pH, partially digested foods, fats, or hypertonic solution in duodenum when stomach begins to empty Intestinal (enteric) gastrin release to blood Intestinal phase Are Stimuli Brief effect Figure 23.17 Stimulate Inhibit Are Stimuli • to move a small bit of chyme into duodenum so as to protect it from over-distension Release of intestinal Hormones: Cholecystokinin (CCK) and Secretin TO BE CONTINUED ON SLIDE #

25. READ B. Small Intestine 1. Gross Anatomy-- Length 20 feet • Subdivisions: Duodenum (10 inches), Jejunum, and Ileum • PlicaeCirculares—deep inner folds • Duodenum • Functions: Most chemical digestion occurs here & it receives bile from liver & enzymes and bicarbonate from pancreas i) Hepatopancreatic Ampulla: Bulb-like point where Bile duct and main pancreatic duct join • Major Duodenal Papilla: Small intestine Duodenum Jejunum Ileum Opening into Duodenum for entry of bile from the Liver and digestive enzymes and bicarbonate from Pancreas Bile & Pancreatic Ducts Major Duodenal Papilla Hepatopancreatic Ampulla Plicae Circulares

26. Major duodenal papilla b) Jejunum • Attached to Duodenum c) Ileum • Attached to Jejunum and large intestine • Both framed by Large Intestine Bile duct and sphincter Plicae Circulares Main pancreatic duct and sphincter Hepatopancreatic ampulla and sphincter Duodenum READ

27. 2. Microscopic Anatomy … a. Mucosa w/ folds & loops *= Contain: Blood vessels, nerves, and lacteal ii) *Cells with Microvilli: Digestive Enzymes embedded in microvilli *Function of folds and loops: READ & Fill in

28. 2. Microscopic Anatomy Small Intestine

29. Small Intestine

30. 2. Microscopic Anatomy … READ ii) Intestinal Glands or Crypts = tubular glands beneath villi formed by folding down of mucosa • Function: produce intestinal juice:water, some mucus, slightly alkaline (pH =7.4-7.8), but low in enzymes • Enteroendocrine cells secrete Cholecystokinin (CCK) and Secretin iii) LamniaPropria - Have agregations of intestinal nodules Lacteal Absorptive cells Goblet cell Vilus Intestinal crypt Enteroendocrine cells Lymphatic vessel Submucosa Duodenal gland

31. Duodenal gland Peyer’s Patches b) Submucosa of small intestine - Areolar Tissue READ • Peyer’s patches = clumps of lymphatic tissue that protect distal regions against bacteria • Have lymphocytes • Duodenal (Brunner’s) glands:in duodenum; secrete alkaline (bicarbonate) mucus to neutralize the acidic chime coming in from stomach. (Enzymes within the small intestine only function in a non-acidic environment.) c. MuscularisExterna d. Serosa Submucosa

33. Small Intestine Submucosa . Brunner’s Glands

34. END PPT  NEXT FILE

35. Review Questions stratified squamous The mucosa of the lower pharanx and esophagus has _________ __________ epithelia. ___________, i.e. swallowing, involves over 22 muscle groups and moves a _________ from the oral cavity to the stomach. Deglutition bolus

36. Review Questions amylase Enzymes in saliva include _________, which is responsible for starch breakdown. 2I, 1C, 2PM, 3M

37. Review Questions Short reflexes of the GI tract are housed and completed within _____ ____ ______ while _______ reflexes involve the CNS. enteric nerve plexuses long

38. Review Questions plicae circulares In the small intestine, ___________ __________, __________, and ___________ all contribute to expanding the surface area for adequate __________. villi microvilli absorption

39. Review Questions From the esophagus to the anus, the GI tract contains how many layers? Which 2 layers contain smooth muscle? 4: mucosa, submucosa, muscularis externa, serosa Mucosa & muscularis externa

40. Participating… gastric The _________ phase is responsible for the production of most gastric secretions by releasing the hormone _________. What other 2 hormones promote gastric secretions? gastrin ACh and Histamine

41. Review Questions Parietal gastric intrinsic factor Chief ________ cells of _______ glands produce HCl and ___________ __________. __________ cells produce pepsinogen. What is intrinsic factor for? B12 absorption

42. Serous & Mucous Cells • Water content • Enzyme = • Mucin Control of Salivation: Parasym. Sys. via chemo- & mechano-receptors 100 million bacteria/mL of saliva!

43. Homeostatic Imbalance • Peptic or gastric ulcers: erosion of stomach wall • Helicobacter pylori bacteria Bacteria Mucosa layer of stomach (b) H. pylori bacteria (a) A gastric ulcer lesion

44. Propulsion& Segmentation From mouth (a)Peristalsis: successive waves of contraction move food distally (1-way). (b) Segmentation: Food mixing/slow food propulsion occurs. Figure 23.3

45. Glands in submucosa • Epithelium • Lamina propria • Muscularis mucosae Submucosa • Longitudinal muscle • Circular muscle • Epithelium • Connective tissue Lumen Gland in mucosa Mucosa-associated lymphoid tissue (MALT) #6 Histology of Alimentary Canal … Mucosa Muscularis externa Serosa Nerve Artery Vein Lymphatic vessel Mesentery