1. Introduction to the Digestive System For student copy

2. Digestive system & homeostasis Digestive system contributes to homeostasis of body by breaking down food into forms that can be absorbed & used by body cells. also: – absorbs : water, vitamins, minerals – eliminates: wastes

3. 2 groups of organs: GI TractAccessory Organs aka Alimentary Canal continuous tube mouth  anus mouth most of pharynx esophagus stomach small & large intestine teeth tongue salivary glands liver gallbladder pancreas

4. vocabulary Ingestion: eating Secretion: ~7 liters water, acids, buffers, & enzymes into lumen of GI tract Motility: contraction/relaxation of smooth muscle in wall of GI tract mix & propel food & secretions  anus Mechanical Digestion: physically breaking down food Chemical Digestion: Absorption Defecation: wastes leave body/ material defecated called feces/ gas called flatus

5. Layers of the gi tract (inner  outer) 1.mucosa 2.submucosa 3.muscularis 4.serosa

6. Mucosa: 3 layers 1.epithelium – mouth  esophagus: stratified sq. epith for protection – stomach  intestines: simple columnar – cells slough off q 5-7 d – exocrine mucus glands (mucus & water) & several types endocrine glands called enteroendocrine cells interspersed

7. Mucosa: 2 nd layer: lamina propia areolar CT rich in blood & lymph vessels contains most of MALT (mucosa- associated lymphatic tissue)

8. Mucosa: 3 rd layer: muscularis mucosa thin layer of smooth muscle creates small folds in epithelium  increases surface area for digestion & absorption

9. submucosa areolar CT that binds mucosa to muscularis rich blood & lymphatics, glands submucosal plexus: extensive network of neurons

10. Muscularis skeletal muscle in mouth, pharynx, superior & middle parts of esophagus, external anal sphincter – voluntary swallowing & defecation 2 sheets smooth muscle in rest of GI tract with myenteric plexus between them 1.outer longitudinal 2.inner circular

11. Serosa parts of GI tract suspended in abdominopelvic cavity have this superficial layer = visceral peritoneum esophagus lacks a serosa; has adventitia a single layer of areolar CT

12. Innervation of the gi tract

13. Enteric Nervous System (ENS) 100 million neurons that extends from esophagus  anus 2 plexuses: 1.myenteric plexus (plexus of Auerbach) – motor neurons of longitudinal & circular muscle 2.submucosal plexus (plexus of Meissner) – w/in submucosa supplying the secretory cells

14. ANS parasympathetic fibers via X to most of GI tract (not to 2 nd ½ large intestine: gets it from sacral spinal cord) – increase secretions & motility sympathetic fibers from thoracic & upper lumbar spinal nerves – decrease secretions & motility

15. Peritoneum largest serous membrane of body simple squamous epithelium with underlying areolar CT divided: 1.parietal peritoneum 2.visceral peritoneum

16. Peritoneal Cavity space between parietal & visceral peritoneums – contains serous fluid: decreases friction – Ascites: excess serous fluid ass’c w/ some diseases

17. Retroperitoneal “behind peritoneum” kidneys & most of pancreas, end of sigmoid colon under parietal peritoneum

18. 5 Major Peritoneal Folds 1.greater omentum 2.falciform ligament 3.lesser omentum 4.mesentery 5.mesocolon

19. Greater Omentum largest peritoneal fold “fatty apron” drapes over transverse colon & coils of sm intestine extends downward anterior to sm intestine contains adipose cells, macrophages, plasma cells; function to combat & contain infections

20. Greater omentum

21. Falciform Ligament attaches liver to anterior abdominal wall & diaphragm – liver only organ in abdominopelvic cavity attached to anterior abd wall

22. Lesser Omentum arises as 2 folds in serosa of stomach & duodenum

23. Mesentery fold of peritoneum that attaches small intestine to posterior abdominal wall – starts @ posterior wall  wraps around sm intestine  reflects back to posterior abd wall – route of bld supply to sm intestine

24. Mesocolon binds large intestine to posterior abd wall route of blood supply, lymphatic drainage

25. Peritonitis acute inflammation of the peritoneum: contamination by infectious microbes – from punctures of abdominal organs trauma surgical wounds