Histology of Digestive Tube

University:
American Career College
Course:
MICR112 | General Microbiology
Academic year:

2020
Views:

189

Pages:

48
Author:

Callie Nielsen

Histology of Digestive Tube 1 Digestive Tract Digestive canal is consists of : Esophagus Stomach Small Intestine Large Intestine Rectum Anus Functions of Epithelium in Digestive Tract Transport and digest food Secretes different types of enzymes Absorb nutrients Produce and secrete hormones involved in digestion Common Structure of Digestive Tract – tube of varying diameter with wall made up of 4 layers Mucosa Submucosa Muscularis externa Serosa or adventitia Mucosa  Epithelial lining – Stomach to colon is simple columnar – Other areas are mostly stratified squamous  Lamina propria is a loose connective tissue with blood and lymphatic vessels, glands and lymphoid nodules  Muscularis mucosa is composed of an inner circular layer and an outer longitudinal layer of smooth muscle Submucosa dense irregular connective tissue Blood and lymph vessels Nerve plexus(Meissner’s plexus) Glands and lymphoid nodules sometimes present Muscularis Externa In most regions muscularis externa consists of inner circular and outer longitudinal layers of smooth muscle In the stomach a third layer is present, an inner oblique layer inside the circular and longitudinal layers Neuron plexuses including the myenteric plexus (Auerbach’s plexus) are found between the two muscle layers Serosa or Adventitia loose connective tissue rich in blood and lymphatic vessels Simple squamous layer of mesothelium presented when an organ is intraperitoneal and it is known as serosa Esophagus  Esophagus is a muscular conduit for foods which are moving to stomach Esophagus Mucosa has a thick stratified squamous nonkeratinized epithelium Mucous glands known as esophageal cardiac glands are in lamina propria near the junction with stomach (cardia) and pharynx Stratified squamous Small Tubuloalveolar - compound • Esophageal glands proper ( submucosa ) • Esophageal cardiac glands ( lamina propria ) Figure 15-12 Copyright © McGraw-Hill Companies Stomach Stomach has 4 regions known as cardia, fundus, body, and pylorus Stomach Mucosa simple columnar mucous Surface epithelium invaginates into lamina propria forming gastric pits Gastric glands open at the base of pits Lamina propria composed of loose CT with smooth muscle and glands Cells of Gastric Gland There is 6 different cell types: Surface lining cells Mucous neck cells Regenerative (stem) cells Parietal cells Chief (Zymogenic) cells DNES (APUD or Entroendocrine cells) • pepsinogen & a weak lipase • pepsinogen to pepsin ( proteolytic enzyme ) • secretory granules • abundant rER • Tubulovesicular system varies with HCl secretory activity. • ↑ HCl activity ↑number of microvilli and ↓tubulovesicular system. Simple , branched , tubular glands cells Copyright © McGraw-Hill Companies Cardiac glands •Tubular gland occasionally branched • mainly mucus-secreting cells with Enteroendocrine cells • Flattened basal nucleus • Apical cytoplasm filled with mucin granules Pyloric gland • pyloric antrum • branched , coiled , tubular • Enteroendocrine cells • half the thickness of the mucosa Small Intestine functions : completion of digestion and absorption of nutrients It has 3 segments: duodenum, jejunum, and ileum Small intestines Small intestines: Duodenum Jejunum Ileum 3 x 10 x 20 = 600 Small Intestine – At the base of villi are simple tubular glands known as crypts of Lieberkuhn – Crypts have the following cells: – Regenerative cells (stem cells) – Absorptive cells – Goblet cells – Paneth cells – M cells – Entroendocrine cells Figure 15-22 Copyright © McGraw-Hill Companies Goblet cells Intestinal crypts or glands, with Paneth cells Figure 15-26 Copyright © McGraw-Hill Companies Duodenal (Brunner) glands Figure 15-29 Copyright © McGraw-Hill Companies Brunner’s gland Brunner’s gland are branched, tubuloalveolar glands whose secretory portions resemble mucous acini Circular folds (plicae circulares) of the jejunum. Figure 15-23 Copyright © McGraw-Hill Companies Ileum Copyright © McGraw-Hill Companies Large Intestine(Colon) Colon has no villi Epithelium is columnar with short microvilli The absorptive cells are the most numerous cell type Functions of epithelium include water absorption, mucous production and feces formation Lamina propria has lymphoid cells and some nodules Figure 15-32 Copyright © McGraw-Hill Companies Muscularis externa has typical circular layer; longitudinal layer forms 3 bands known as the taeniae coli Colon Colon Appendix Appendix is an evagination of large intestine It has a narrow lumen with abundant lymphoid follicles Rectum  Rectum resembles the colon  The mucosa contains numerous goblet cells  The muscularis externa has both inner circular and outer longitudinal smooth muscle layers, no teniae coli Anal Canal  In anal canal the crypts are short and few and in distal half there is no crypts  Mucosa of has longitudinal folds, the anal columns (rectal columns of Morgagni)