6th a pre lab digestive system git
DESCRIPTION
aasTRANSCRIPT
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The Digestive System
Gastrointestinal tract (GIT)and the
Accessory organs and glands
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General Histological Features
L
EpitheliumLamina
propriaMuscularis
mucosae
1. Mucos
a
2. Submucosa
Inner circular
Outer longitudinal
3. Musculari
sexterna
4. Serosa / adventit
ia
*Myenteric plexus/ Auerbachs plexus
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Pharynx
Respiratory pharynx oropharynxSuperior portionLined by respiratory epithelium
Inferior portionLined by nonkeratinized stratified squamous epithelium
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Esophagus Characteristic features:
Mucosa lined by nonkeratinized stratified squamous epithelium
Submucosa with esophageal glands (varies as to segment)
Muscularis externa Upper portion with skeletal muscles Middle third with mixed skeletal and smooth muscle Lower third with smooth muscle
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Points of comparison
uppermost portion
Middle 1/3 Lower 1/3
1. Muscularis mucosae
Absent in the beginning
PresentPresent
2. Muscularis externa Skeletal muscle
(inner circular & thick outer longitudinal)
Skeletal & smooth muscle
(inner smooth muscle & outer skeletal muscle)
Smooth muscle (inner circular
& outer longitudinal)
3. Submucosal glands Absent few abundant
4.Adventia Only fibrosa Only fibrosa Only serosa
Comparison Between various Portions of Esophagus
* Presence of glands at transition between middle and lower 1/3
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Esophageal glands
Smoothmuscle
Skeletalmuscle
Esophageal glands
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Stomach Characteristic features:
Mucosa is complex 2-3 layers muscularis mucosae Gastric glands Gastric pits
Presence of rugae
Muscularis externa (3 layers) Inner oblique Middle circular Outer longitudinal
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Variations in the glands (crypts, pits, ducts)
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Esophageal-gastric junction
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* * * * ***
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Gastric mucosa epithelial cell types:
Surface mucous cells
Undifferentiated cells
Neck mucous cells
Parietal/oxyntic cells
Chief/zymogenic cells
Enteroendocrine cells
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Small intestine(duodenum, jejunum, ileum)
Characteristic features:
Composition and organization of mucosa
Plicae circularis/ valves of Kerckring
Muscularis externa (2-layered)
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Mucosa of the Small intestine:
Presence of villi
Intestinal glands/ Krypts of Lieberkuhn
Enterocytes/absorptive cells
Goblet cells
M cells
Paneth cells
Enteroendocrine cells &Undifferentiated cells
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Regional differences
Duodenum
Presence of Brunners gland in the submucosa
Typically with leaflike to fingerlike villi
Relatively few goblet cells**
*
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* *
*
*
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Jejunum
neither Brunners glands nor Peyers patches
With long leaflike villi
Many plicae circularis
Intermediate number of goblet cells
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Ileum
Lamina propia with many Peyers patches
With short, broad-tipped villi
Relatively abundant goblet cells
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Large intestine/colon
Mucosa
with simple columnar epithelium Abundant goblet cells Absence of villi Deep cyrpts of Lieberkuhn
No mucosal folds except in the rectum (rectal columns of Morgagni)
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Submucosa Hemorrhoidal plexus of veins ( in the lower rectum)
Muscularis externa Smooth muscle (longitudinal bands) *** taeniae coli
Adventitia/Serosa
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Anal canal Mucosa
with short crypts ---disappearing (1st 2 cm) Stratified squamous epithelium (to the opening)
Submucosa with sebaceous glands and sweat glands
Muscularis externa with thickened inner circular smooth muscle
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Appendix
Resembles the colon except for:
relatively small lumen
Fewer and shorter crypts
More lymphoid nodules
Without taeniae coli