Transcript Layers of the digestive tube - Chicagoland Jewish High School

Digestion
Structure of the wall of the GI tract
Sphincters
Gastric emptying
Vomiting
Exocrine glands
Have ducts
Epithelium is
continuous w/ body
surface
Ex: Salivary, gastric
glands, pancreas, bile
glands in liver, sweat
glands
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/ExocrineGlands.html
Wall of the GI Tract
Mucous Membrane
Epithelium (varies)
Lamina propria
(Connective tissue)
Muscularis Mucosa
(smooth muscle)
Submucosa
Muscularis Externa, Serosa
Muscularis Externa: 2 layers of smooth muscle
Inner circular fibers
Outer longitudinal fibers
Neural network in between
Enteric nervous system
Serosa: outermost layer
Connective tissue
Squamous cells
Muscularis Externa Layers
Sphincters
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UES
LES
Pyloric
Ileocecal
Internal anal
External anal
GI secretions
Gastric:
Gastrin:  gastric juice secretion
Enterogastrones:
Secretin:  bicarbonate from pancreas
• CCK:
• bile (contractions from gall bladder) in response
to amino, fatty acids
• pancreatic enzymes
Gastric Emptying
Needs to be mediated so rate of emptying into
the small intestine isn’t greater than rate of small
intestine processing
Presence of acid in the duodenom secretin 
closes pyloric sphincter, stimulates secretions of
the pancreas
Presence of fat: release of CCK  closes
pyloric sphincter
Presence of peptides/amino acids: release of
gastrin  closes pyloric sphincter
Yaking, spewing, blowing chunks,
hurling, etc. (vomiting)
Reflex, expulsion of stomach/duodenal
contents
Retching: contents forced into
esophagus, not up to pharynx
Reverse peristalsis
Pyloric sphincter relaxes
Yaking (continued)
“vomiting center” in medulla signaled by:
Distension of stomach, pressure in the back of
the throat
Injury to urogenital area
Dizziness
Emetics: stimulate stomach/duodenum
receptors to induce vomiting
Ex: ipecac