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
Mouth (oral cavity) Tongue Parotid gland Sublingual gland Submandibular gland Salivary glands Esophagus Liver Gallbladder Small intestine Anus Duodenum Jejunum Ileum Pharynx Stomach Pancreas (Spleen) Transverse colon Descending colon Ascending colon Cecum Sigmoid colon Rectum Vermiform appendix Anal canal Large intestine Figure 23.1
Vein carrying blood to hepatic portal vessel Muscle layers Circular folds Villi Lumen (a) Figure 23.22a
Microvilli (brush border) Absorptive cells Lacteal Goblet cell Blood capillaries Mucosa associated lymphoid tissue Intestinal crypt Muscularis mucosae Duodenal gland (b) Vilus Enteroendocrine cells Venule Lymphatic vessel Submucosa Figure 23.22b
Microvilli (b) Absorptive cell 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 capillaries Mucosa associated lymphoid tissue Intestinal crypt Muscularis mucosae Duodenal gland (b) Villus Enteroendocrine cells Venule Lymphatic vessel Submucosa 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 (inactive) Procarboxypeptidase (inactive) Chymotrypsin Carboxypeptidase 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 Gallbladder Major duodenal papilla Hepatopancreatic ampulla and sphincter Duodenum Tail of pancreas Pancreas Jejunum Main pancreatic duct and sphincter 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
Hepatic veins Liver Hepatic portal vein Small intestine Inferior vena cava (not part of hepatic portal system) Gastric veins Spleen Inferior vena cava Splenic vein Right gastroepiploic vein Inferior mesenteric vein Superior mesenteric vein 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 hepatocytes Bile canaliculi Bile duct (receives bile from bile canaliculi) Fenestrated lining (endothelial cells) of sinusoids Portal vein Hepatic macrophages in sinusoid walls Bile duct Portal venule Portal arteriole Portal triad (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 Nipple Liver Bare area Falciform ligament Left lobe of liver Right lobe of liver Gallbladder (a) Round ligament (ligamentum 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 Gallbladder Major duodenal papilla Hepatopancreatic ampulla and sphincter Duodenum Tail of pancreas Pancreas Jejunum Main pancreatic duct and sphincter 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 NaHCO 3 to duodenum via pancreatic duct Tissue types Endocrine o Islets of Langerhans insulin and glucagon Exocrine o Acinar tissue pancreatic juice
Mouth (oral cavity) Tongue Parotid gland Sublingual gland Submandibular gland Salivary glands Esophagus Liver Gallbladder Small intestine Anus Duodenum Jejunum Ileum Pharynx Stomach Pancreas (Spleen) Transverse colon Descending colon Ascending colon Cecum Sigmoid colon Rectum Vermiform appendix Anal canal Large intestine 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 Gallbladder Major duodenal papilla Hepatopancreatic ampulla and sphincter Duodenum Tail of pancreas Pancreas Jejunum Main pancreatic duct and sphincter Head of pancreas Figure 23.21
Small duct Acinar cells Basement membrane Zymogen granules (a) Rough endoplasmic reticulum 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 (hepatic) flexure Transverse colon Superior mesenteric artery Haustrum Ascending colon IIeum IIeocecal valve Cecum Vermiform appendix (a) Rectum Anal canal Left colic (splenic) flexure Transverse mesocolon Epiploic appendages Descending colon Cut edge of mesentery Teniae coli Sigmoid colon External anal sphincter 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 (d) Urinary bladder Rectum 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 cerebral cortex (conscious control) Voluntary motor nerve to external anal sphincter External anal sphincter (skeletal muscle) Rectum Sensory nerve fibers Sigmoid colon 1 Distension, or stretch, of the rectal walls due to movement of feces into the rectum stimulates stretch receptors there. The receptors transmit signals along afferent fibers to spinal cord neurons. 2 A spinal reflex is initiated in which parasympathetic motor (efferent) fibers stimulate contraction of the rectal walls and relaxation of the internal anal sphincter. Stretch receptors in wall Involuntary motor nerve (parasympathetic division) Internal anal sphincter (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