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Digestive System Part Business Reminder: No class Monday (Memorial Day) Midterm 2 is Tuesday 5/28/13 Optional review session tomorrow @ 5pm Homework due in Lab 1. PreLab 8 (1pt) 2. Replace a Missing Assignment (4 pts) Homework page 17 Digestive System Part 2 Digestive System Small intestine Major organ of digestion and absorption 2 - 4 m long; from pyloric sphincter to ileocecal valve Subdivisions Duodenum Jejunum Ileum Digestive System Small intestine Structural modifications Villi Intestinal glands Mucosa Submucosa Parotid gland Mouth (oral cavity) Sublingual gland Salivary Tongue Submandibular glands gland Esophagus Pharynx Stomach Pancreas Liver (Spleen) Gallbladder Transverse colon Duodenum Descending colon Small Jejunum Ascending colon intestine Ileum Cecum Large Sigmoid colon intestine Rectum Vermiform appendix Anus Anal canal Figure 23.1 Vein carrying blood to hepatic portal vessel Muscle layers Lumen Circular folds Villi (a) Figure 23.22a Microvilli (brush border) Absorptive cells Lacteal Goblet cell Blood Vilus capillaries Mucosa associated lymphoid tissue Enteroendocrine Intestinal crypt cells Muscularis Venule mucosae Lymphatic vessel Duodenal gland Submucosa (b) Figure 23.22b Microvilli Absorptive cell (b) Figure 23.3b Digestive System Chemical digestion in the small intestine Food entering SI = partially digested Intestinal juice Water, mucous Crypt cells produce lysozyme Microvilli (brush border) Absorptive cells Lacteal Goblet cell Blood Villus capillaries Mucosa associated lymphoid tissue Enteroendocrine Intestinal crypt cells Muscularis Venule mucosae Lymphatic vessel Duodenal gland Submucosa (b) Figure 23.22b Digestive System Chemical digestion in the small intestine Pancreatic juice Enzymes Amylase o Carbohydrates Lipase o Fats Trypsinogen, chymotrypsinogen, carboxypeptidase o Activated to digest protein Sodium bicarbonate Neutralize stomach acid Stomach Pancreas Epithelial cells Membrane-bound enteropeptidase Trypsinogen Trypsin (inactive) Chymotrypsinogen Chymotrypsin (inactive) Procarboxypeptidase Carboxypeptidase (inactive) Figure 23.27 Digestive System Chemical digestion in the small intestine Bile Emilsify lipids Disaccharidases and peptidases Protective mucous secreted as well Right and left hepatic ducts of liver Cystic duct Common hepatic duct Bile duct and sphincter Accessory pancreatic duct Mucosa with folds Tail of pancreas Gallbladder Pancreas Major duodenal Jejunum papilla Main pancreatic duct Hepatopancreatic and sphincter ampulla and sphincter Duodenum Head of pancreas Figure 23.21 Digestive System Accessory digestive organs Liver Pancreas Gallbladder Digestive System Accessory digestive organs Liver Largest internal surface area of any body organ Blood supply Hepatic artery Hepatic-portal vein Hepatic vein Inferior vena cava (not part of hepatic portal system) Gastric veins Hepatic veins Spleen Inferior vena cava Liver Splenic vein Right gastroepiploic Hepatic portal vein vein Inferior mesenteric vein Superior mesenteric vein Small intestine Large intestine Rectum (c) The hepatic portal circulation. Copyright © 2010 Pearson Education, Inc. Figure 19.29c Interlobular veins (to hepatic vein) Central vein Sinusoids Plates of Bile canaliculi hepatocytes Bile duct (receives bile from bile canaliculi) Fenestrated lining (endothelial cells) of sinusoids Bile duct Hepatic Portal venule Portal triad macrophages Portal arteriole in sinusoid walls Portal vein (c) Copyright © 2010 Pearson Education, Inc. Figure 23.25c Digestive System Accessory digestive organs Liver Microscopic compartments = lobules Lined by hepatocytes = screen blood o Store nutrients o Manage toxins Sternum Bare area Nipple Falciform Liver ligament Left lobe of liver Right lobe of liver Round ligament Gallbladder (ligamentum (a) teres) Figure 23.24a (a) Lobule (b) Central vein Connective tissue septum Copyright © 2010 Pearson Education, Inc. Figure 23.25a, b Digestive System Accessory digestive organs Liver Hepatocyte functions Process blood borne nutrients Store fat-soluble vitamins Perform detoxification Produce ~900 ml bile per day Glucose is stored as glycogen Cystic, Hepatic and Bile ducts Right and left hepatic ducts of liver Cystic duct Common hepatic duct Bile duct and sphincter Accessory pancreatic duct Mucosa with folds Tail of pancreas Gallbladder Pancreas Major duodenal Jejunum papilla Main pancreatic duct Hepatopancreatic and sphincter ampulla and sphincter Duodenum Head of pancreas Copyright © 2010 Pearson Education, Inc. Figure 23.21 Digestive System Accessory digestive organs Liver Bile Yellow-green, alkaline solution Bile salts o Cholesterol derivatives that function in fat emulsification & absorption Bilirubin o Pigment formed from heme o Metabolized to form urobilinogen → stercobilin Lack of bile = grayish stools with fatty streaks (acholic feces) Digestive System Accessory digestive organs Liver Other functions Makes heparin and other plasma proteins Stores vitamins, minerals and lipid soluble toxins Stores nutrients Catabolizes nitrogenous wastes Digestive System Accessory digestive organs Liver Gallbladder Thin-walled muscular sac on the ventral surface of the liver Stores and concentrates bile by absorbing its water and ions Releases bile via the cystic duct o Flows into the bile duct Digestive System Accessory digestive organs Pancreas Function Delivers digestive fluids and NaHCO3 to duodenum via pancreatic duct Tissue types Endocrine o Islets of Langerhans → insulin and glucagon Exocrine o Acinar tissue → pancreatic juice Parotid gland Mouth (oral cavity) Sublingual gland Salivary Tongue Submandibular glands gland Esophagus Pharynx Stomach Pancreas Liver (Spleen) Gallbladder Transverse colon Duodenum Descending colon Small Jejunum Ascending colon intestine Ileum Cecum Large Sigmoid colon intestine Rectum Vermiform appendix Anus Anal canal Figure 23.1 Digestive System Accessory digestive organs Pancreas Secretion mediated by hormones Secretin o Released in response to acid o Stimulates release of base from pancreas o Also stimulates release of pancreatic secretions and bile Cholecystokinin o Released when protein and fat enter intestine o Stimulates the release of pancreatic secretions and bile Right and left hepatic ducts of liver Cystic duct Common hepatic duct Bile duct and sphincter Accessory pancreatic duct Mucosa with folds Tail of pancreas Gallbladder Pancreas Major duodenal Jejunum papilla Main pancreatic duct Hepatopancreatic and sphincter ampulla and sphincter Duodenum Head of pancreas Figure 23.21 Small duct Acinar cells Basement membrane Zymogen granules Rough endoplasmic reticulum (a) Figure 23.26a Digestive System Large intestine About 1.5 meters in length in a cadaver (SI about 6m long) Functions Vitamins, water, and electrolytes are reclaimed Propulsion of feces toward the anus Colon is not essential for life Right colic Left colic (hepatic) (splenic) flexure flexure Transverse Transverse mesocolon colon Epiploic Superior appendages mesenteric artery Descending Haustrum colon Ascending Cut edge of colon mesentery IIeum Teniae coli IIeocecal valve Sigmoid Cecum colon Vermiform appendix Rectum Anal canal External anal sphincter (a) Figure 23.29a Digestive System Regions Cecum Colon Rectum Anal canal Digestive System Regions Cecum Blind pouch Appendix attaches to this area Bacteria Immune function Digestive System Regions Colon Ascending Retroperitoneal Transverse Anchored via mesocolons (mesenteries) Descending Retroperitoneal Sigmoid Anchored via mesocolons (mesenteries) Greater omentum Transverse colon Transverse mesocolon Descending colon Jejunum Mesentery Sigmoid mesocolon Sigmoid colon Ileum (c) Figure 23.30c Liver Lesser omentum Pancreas Stomach Transverse mesocolon Duodenum Transverse colon Mesentery Greater omentum Jejunum Ileum Visceral peritoneum Parietal peritoneum Urinary bladder Rectum (d) Figure 23.30d Digestive System Regions Rectum Rectal valves stop feces from being passed with gas Anal canal Last segment of the large intestine Internal anal sphincter Smooth muscle (involuntary) Spinal reflex arcs External anal sphincter Skeletal muscle (voluntary) Rectal valve Rectum Hemorrhoidal veins Levator ani muscle Anal canal External anal sphincter Internal anal sphincter Anal columns Pectinate line Anal sinuses Anus (b) Figure 23.29b Digestive System Defecation Mass movements force feces into rectum Distension initiates spinal defecation reflex Parasympathetic signals Stimulate contraction of the sigmoid colon and rectum Relax the internal anal sphincter Conscious control allows relaxation of external anal sphincter Valsalva’s maneuver Impulses from 1 Distension, or stretch, of the cerebral cortex rectal walls due to movement of feces into the rectum (conscious stimulates stretch receptors control) Sensory there. The receptors transmit signals along afferent fibers to nerve fibers spinal cord neurons. Voluntary motor 2 A spinal reflex is initiated in nerve to external which parasympathetic motor anal sphincter Sigmoid (efferent) fibers stimulate colon contraction of the rectal walls and relaxation of the internal anal sphincter. Stretch receptors in wall Rectum Involuntary motor nerve External anal (parasympathetic division) sphincter Internal anal sphincter (skeletal muscle) (smooth muscle) 3 If it is convenient to defecate, voluntary motor neurons are inhibited, allowing the external anal sphincter to relax so that feces may pass. Figure 23.31 .
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