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The Digestive System: Large Intestine and Liver

This article provides an overview of the gross and microscopic anatomy of the large intestine and liver, including their functions and structures. It also discusses the role of the gallbladder in storing and expelling bile.

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The Digestive System: Large Intestine and Liver

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  1. PART 3 The Digestive System

  2. 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

  3. 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

  4. 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

  5. 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

  6. Gross Anatomy of Large Intestine Figure 22.22a

  7. Gross Anatomy of Large Intestine Figure 22.22b

  8. 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

  9. 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

  10. Defecation Reflex Figure 22.23

  11. 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

  12. Mucosa of the Large Intestine Figure 22.24

  13. The Liver • Largest gland in the body • Performs over 500 functions • Digestive function • Bile production • Performs many metabolic functions

  14. Visceral Surface of the Liver Figure 22.26

  15. Microscopic Anatomy of the Liver • Hepatocyte – functional cells of the liver • Portal triad composed of • Bile duct tributary • Branch of hepatic portal vein • Branch of hepatic artery • Kupffer cells – destroy bacteria

  16. Microscopic Anatomy of the Liver • Some functions of hepatocytes • Rough ER manufactures blood proteins • Smooth ER produces bile salts, detoxifies poisons • Peroxisomes detoxify poisons (alcohol) • Golgi apparatus packages secretory products • Mitochondria provide energy for liver processes • Glycosomes store sugar • Great capacity for regeneration

  17. Microscopic Anatomy of Liver Figure 22.27a, c, d

  18. The Gallbladder • Stores and concentrates bile • Expels bile into duodenum • Bile emulsifies fats • Cholecystokinin – released from enteroendocrine cells in response to fatty chyme

  19. The Gallbladder Figure 22.20

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