The Digestive System PDF

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Digestive System Part B 23 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson E...

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Digestive System Part B 23 Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Esophagus ▪ Muscular tube going from the laryngopharynx to the stomach ▪ Travels through the mediastinum and pierces the diaphragm ▪ Joins the stomach at the cardiac orifice Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Deglutition (Swallowing) Bolus of food Tongue Uvula Pharynx Bolus Epiglottis Epiglottis Glottis Trachea Esophagus Bolus (a) Upper esophageal (b) Upper esophageal (c) Upper esophageal sphincter contracted sphincter relaxed sphincter contracted Relaxed Relaxed muscles muscles Circular muscles contract, constricting passageway and pushing Gastroesophageal Bolus of food bolus down sphincter open Longitudinal muscles contract, shortening passageway ahead of bolus Gastroesophageal sphincter closed Stomach (d) (e) Figure 23.13 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Stomach ▪ Chemical breakdown of proteins begins and food is converted to chyme ▪ Cardiac region – surrounds the cardiac orifice ▪ Fundus – dome-shaped region beneath the diaphragm ▪ Body – midportion of the stomach ▪ Pyloric region – made up of the antrum and canal which terminates at the pylorus ▪ The pylorus is continuous with the duodenum through the pyloric sphincter Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Stomach ▪ Greater curvature – entire extent of the convex lateral surface ▪ Lesser curvature – concave medial surface ▪ Lesser omentum – runs from the liver to the lesser curvature ▪ Greater omentum – drapes inferiorly from the greater curvature to the small intestine Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Stomach ▪ Blood supply – celiac trunk, and corresponding veins (part of the hepatic portal system) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Stomach Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23.14a  Microscopic Anatomy of the Stomach ▪ Muscularis – has an additional oblique layer that: ▪ Epithelial lining is composed of: ▪ Goblet cells that produce a coat of alkaline mucus ▪ The mucous surface layer traps a bicarbonate- rich fluid beneath it ▪ Gastric pits contain gastric glands that secrete gastric juice, mucus, and gastrin Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Microscopic Anatomy of the Stomach Figure 23.15 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Glands of the Stomach Fundus and Body ▪ Gastric glands of the fundus and body have a variety of secretory cells ▪ Mucous neck cells – secrete acid mucus ▪ Parietal cells – secrete HCl Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Small Intestine: Gross Anatomy ▪ Runs from pyloric sphincter to the ileocecal valve ▪ Has three subdivisions: duodenum, jejunum, and ileum ▪ The bile duct and main pancreatic duct: ▪ Join the duodenum at the hepatopancreatic ampulla ▪ The jejunum extends from the duodenum to the ileum ▪ The ileum joins the large intestine at the ileocecal valve Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Small Intestine: Microscopic Anatomy ▪ Structural modifications of the small intestine wall increase surface area ▪ Villi – fingerlike extensions of the mucosa ▪ Microvilli – tiny projections of absorptive mucosal cells’ plasma membranes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Small Intestine: Microscopic Anatomy Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23.21  Small Intestine: Histology of the Wall ▪ The epithelium of the mucosa is made up of: ▪ Absorptive cells and goblet cells Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Small Intestine: Histology of the Wall ▪ Cells of intestinal crypts secrete intestinal juice ▪ Peyer’s patches are found in the submucosa ▪ Brunner’s glands in the duodenum secrete alkaline mucus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Liver ▪ The largest gland in the body ▪ Superficially has four lobes – right, left, caudate, and quadrate ▪ The falciform ligament: ▪ Separates the right and left lobes anteriorly ▪ Suspends the liver from the diaphragm and anterior abdominal wall Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Liver ▪ The ligamentum teres: ▪ Is a remnant of the fetal umbilical vein ▪ Runs along the free edge of the falciform ligament Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Liver: Associated Structures ▪ The lesser omentum anchors the liver to the stomach ▪ The hepatic blood vessels enter the liver at the porta hepatis ▪ The gallbladder rests in a recess on the inferior surface of the right lobe Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Liver: Associated Structures ▪ Bile leaves the liver via: ▪ Bile ducts, which fuse into the common hepatic duct ▪ The common hepatic duct, which fuses with the cystic duct ▪ These two ducts form the bile duct Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Gallbladder and Associated Ducts Figure 23.20 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Liver: Microscopic Anatomy ▪ Hexagonal-shaped liver lobules are the structural and functional units of the liver ▪ Composed of hepatocyte (liver cell) plates radiating outward from a central vein ▪ Portal triads are found at each of the six corners of each liver lobule ▪ Portal triads consist of a bile duct and ▪ Hepatic artery – supplies oxygen-rich blood to the liver ▪ Hepatic portal vein – carries venous blood with nutrients from digestive viscera Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Liver: Microscopic Anatomy ▪ Liver sinusoids – enlarged, leaky capillaries located between hepatic plates ▪ Kupffer cells – hepatic macrophages found in liver sinusoids Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Liver: Microscopic Anatomy ▪ Hepatocytes’ functions include: ▪ Production of bile ▪ Processing bloodborne nutrients ▪ Storage of fat-soluble vitamins ▪ Detoxification Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Microscopic Anatomy of the Liver Figure 23.24c, d Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The Gallbladder ▪ Thin-walled, green 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, which flows into the bile duct Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Large Intestine ▪ Is subdivided into the cecum, appendix, colon, rectum, and anal canal ▪ The saclike cecum: ▪ Lies below the ileocecal valve in the right iliac fossa ▪ Contains a wormlike vermiform appendix Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Large Intestine Figure 23.29a Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Colon ▪ Has distinct regions: ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, and sigmoid colon ▪ The transverse and sigmoid portions are anchored via mesenteries called mesocolons ▪ The sigmoid colon joins the rectum ▪ The anal canal, the last segment of the large intestine, opens to the exterior at the anus Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Mesenteries of Digestive Organs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23.30b  Mesenteries of Digestive Organs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23.30c  Mesenteries of Digestive Organs Figure 23.30d Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings