PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 22

HUMAN ANATOMY

fifth edition

PART 3

The Digestive System

MARIEB | MALLATT | WILHELM

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Large Intestine    Digested residue contains few nutrients Small amount of digestion by bacteria Main functions  Absorb water and electrolytes  Mass peristaltic movements force feces toward the rectum Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Gross Anatomy of Large Intestine  Subdivided into  Cecum, vermiform appendix, colon, rectum, anal canal  Special features of large intestine 

Teniae coli

 Thickening of longitudinal muscularis 

Haustra

 Puckering created by teniae coli 

Epiploic appendages

 Fat-filled pouches of visceral peritoneum Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Gross Anatomy of Large Intestine 

Cecum

  Blind pouch Beginning of large intestine 

Vermiform appendix

  Contains lymphoid tissue Neutralizes pathogens  Colon  Divided into distinct segments  Ascending, transverse, descending, and sigmoid colon Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Gross Anatomy of Large Intestine 

Rectum

 Descends along the inferior half of the sacrum 

Anal Canal

  The last subdivision of the large intestine Lined with stratified squamous epithelium Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Gross Anatomy of Large Intestine Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 22.22a

Gross Anatomy of Large Intestine Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 22.22b

Vessels and Nerves of the Large Intestine  First half of large intestine   Arterial supply -

superior mesenteric artery

Innervation  Sympathetic innervation – superior mesenteric and celiac ganglia  Parasympathetic innervation – vagus nerve Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Vessels and Nerves of the Large Intestine  Distal half of large intestine   Arterial supply -

inferior mesenteric artery

Innervation  Sympathetic innervation – inferior mesenteric and hypogastric plexuses  Parasympathetic innervation – pelvic splanchnic nerves Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Defecation Reflex Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 22.23

Microscopic Anatomy of Large Intestine     Villi are absent Contains numerous goblet cells Intestinal crypts – simple tubular glands Lined with

simple columnar epithelial tissue

 Epithelium changes at anal canal  Becomes

stratified squamous epithelium

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Mucosa of the Large Intestine Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 22.24