Digestive System Histology

Digestive System Objectives To understand the general organization of organs of the digestive system and how they function to obtain metabolites necessary for growth and energy for the body, yet maintain a barrier between the environment and the internal milieu of the body To identify and describe functions of cellular structures, cells, and groups of cells in the digestive system. Function of the Digestive System Movement of food Secretion of digestive juices Absorption of digested foods, water, and electrolytes Ref code # 4, 16 Adaptation of G.I. Tract for Specific Function Function Organ Simple passage from one part to another Esophagus Storage of food or feces Stomach or distal colon Digestion Stomach, small intestine Absorption of end products Small intestine, proximal colon Ref code # 6 32409 Small intestine Large intestine Small intestine General Structure of the Digestive Tract 32409 Epithelium Lamina propria Muscularis mucosa Submucosa Muscularis externa Serosa Ref code #2 General Structure of the Digestive Tract 146 Ref code #6 Epithelium Lamina propria Submucosa Muscularis externa Serosa Small intestine 32409 Small intestine General Structure of the Digestive Tract Large intestine Ref code # 6 153 Epithelium Lamina propria Muscularis mucosa Submucosa Large intestine Stomach Muscularis externa 145 Large intestine Muscularis externa Mesothelium 153 145 153 Stomach Muscularis externa Serosa Inner, thicker circular layer Outer longitudinal layer of the muscularis externa Ref code #5 Non-keratinized stratified squamous epithelium. Skeletal muscle, Mucus and Serous glands, Filiform Papillae Histo 51 FILIFORM PAPILLAE Ref code #6 Slide #12 (1101). Tongue, rabbit. Filiform papillae Skeletal muscle Foliate papillae that possess Taste buds Serous glands Ref code #5 Esophagus Non-keratinized stratified squamous epithelium. Histo 29 Muscularis externa Sub-mucosal glands Skeletal muscle 137 Esophagus – skeletal and smooth muscle Lamina propria Muscularis mucosa Submucosa Muscularis externa Serosa epithelium Lamina propria Sub-mucosal Mucus and Serous glands Esophagus 242 Submucosa Muscularis mucosa Non-keratinized stratified squamous epithelium Skeletal muscle, Muscularis externa Submucosa Perichondrium If outer layer is not covered by mesothelium = adventitia 137 Muscularis externa of the upper esophagus is composed mostly of skeletal muscle Esophagus The muscularis externa in middle to lower esophagus is composed mostly of smooth muscle. Ref code # 5, 6 437 Cardio-esophageal junction Sratified squamous Luminal epithelium changes from stratified squamous to simple columnar epithelium in the cardiac region The stomach have no goblet cells, no brush border on surface cells, and no villi. Ref code #5 Dog cross section of body Liver Pancreas Esophagus Intestine Stomach 145 Fundic stomach Mucosa Antibody-producing plasma cells Gastric pits Submucosa Submucosa Ganglion cells of the Auerbach's plexus regulate the muscularis externa Ganglion cells of the Meissner's plexus regulates muscularis mucosa Muscularis externa 145 Fundic stomach Mucous neck cells Surface mucous cells Gastric pits and gastric glands Chief cells and parietal cells Enteroendocrine cells Mucus neck cells Fundic stomach, rabbit (toluidine blue) 244 Chief cells Parietal cell Enteroendocrine cells Chief cell Enteroendocrine cell Parietal cells Ref code #6 Ref code #5 EM 15 Parietal cell produces 1. HCl 2. Bicarbonate 3. Intrinsic factor for vitamin B12 absorption by gut: needed in red blood cell formation 243 Fundic stomach, monkey (PAS) Mucous neck cells Parietal cells Chief cells Enteroendocrine cells Surface mucous cells 244 Fundic stomach, rabbit (toluidine blue) Parietal cells Gastric pits Surface mucous cells Mucous neck cells Lumen Enteroendocrine cells Lumen Ref code #6 PAS H&E Surface mucus cells EM 16 • Granules of surface mucous cells • Mitochondria • Nuclei Toluidine • Lumenblue Ref code #5 Large granules of chief cell EM 14 • Large granules of chief cell • Granules of an argentaffin cell • Lamina propria • Nuclei Granules of an argentaffin cell 141 Pyloric stomach, monkey (PAS) Pyloric glands Pyloric glands of the stomach contain mucous cells Surface mucus cells Ref code # 5, 6 147 Pyloroduodenal junction, baboon Intestine Lymphoid nodule Stomach Muscularis externa Lamina propria 147 Pyloroduodenal junction, baboon Submucosa Gastric glands Stomach Muscularis mucosa Muscularis externa Gastric pits Intestine Villi Lamina propria Crypts of Lieberkühn (intestinal glands). Junction Goblet cells and intestinal absorptive cells with a brush border Ref code #5 monkey Goblet and absorptive cells, 146 Duodenum, Enteroendocrine cell Crypts of Lieberkühn Muscularis mucosa Lamina propria. Submucosa Submucosal Brunner's glands. 152 Duodenum Brunner’s glands Absorptive cells Goblet cells Paneth cell Enteroendocrine cell Intestinal villus 447 Small intestine Mucus of goblet cells and the carbohydrates in the brush border are PAS positive for sugars Macrophages Intestinal absorptive cell Brush border Intestinal villus Intestinal absorptive cell Brush border Goblet cells 249 PAS Central lacteal EM 17 Basal portion of intestinal absorptive cell 1. Plasma cell 2. Lymphocyte 3. Smooth muscle 4. Intestinal absorptive cell 5. Macrophage 6. Lumen of capillary 7. Pericyte of capillary Goblet cell EM 4. Apical portion of intestinal absorptive cell 1. Microvilli of brush border 2. Droplets of goblet cell 3. Terminal web 4. Lipid in SER 5. lumen Basal portion of intestinal absorptive cell 1. Mitochondria 2. Nuclei of intestinal absorptive cell 3. Smooth muscle of muscularis mucosa 4. Basal lamina EM 4b Brush border of intestinal absorptive cells Mitochondria EM 4c Intestinal absorptive cells in cytoplasm just above the nucleus Nucleus Epithelium Smooth muscle cells Meissner’s plexus cell bodies 32409 (Auerbach's plexus) Nerve cell bodies 152 Duodenum (small intestine) Auerbach's plexus, found in between the circular and longitudinal smooth muscle layers in small intestine Auerbach's plexus Nerve cell bodies 148 Ileum Meissner’s plexus cell bodies in submucosa Paneth cell Submucosa Small intestinal villi 250 Argentaffin cells of Ileum, monkey Paneth cell Enteroendocrine cells also called Argentaffin cells Compare luminal surfaces of the small and large intestines small intestines Villi Ref code #6 large intestines NO Villi Ref code #5 153 Large intestine or Colon, monkey Esophagus Stomach Duodenum Solitary lymph follicles in the lamina propria seen throughout the GI tract help the immune system maintain a barrier between the environment and the internal milieu of the body. Other contributors include luminal epithelium, HCl in the stomach, and mucus produced my many goblet cells in the intestines. Large intestine or Colon, monkey 153 Ileum Human appendix 32412 Ref code #5 Large intestines Anal skin In summary The digestive system functions to obtain metabolites, yet maintain a barrier between the environment and the internal milieu of the body. Questions on the Digestive system 1. Which of these cells is/are found both in the stomach and intestines? a. enteroendocrine (argentaffin cells) b. fibroblasts c. goblet cell d. a and b e. a, b, and c 2. The digestive system functions to obtain metabolites necessary for growth and energy needs; however, it must maintain a barrier between the environment and the internal milieu of the body. Which of the following is the least effective feature of this barrier? a. composition of saliva b. acid environment of the stomach c. large volume of mucus produced into the lumen of the large intestine d. the chylomicron fat absorption mechanism via central lacteal e. nearby and abundant immune defense structures and mechanisms