Flashcards in 14 - GI Anatomy and Histology Deck (57)
Movements of the bowel that influence the transport of luminal contents
Act of taking food into the mouth
Chewing food and moistening it with saliva
Oral contraction and anal relaxation, which is propulsive
Exocrine to lumen of gut, endocrine to blood
Breakdown of ingested macromolecules into absorbable smaller subunits
Transport of end products of digestion to blood and/or lymph
Temporary holding of ingested contents
Getting rid of indigestible material
Sphincters of the gut
Gut Wall - Luminal
Gut Wall - Middle Layer
Gut Wall - Basal
Inner circular muscle
Outer longitudinal muscle
Gut Wall - Non-retroperitoneal parts
Esophagus - To resist abrasion
Stratified squamous nonkeritanized epithelium
Stomach - To digest
Simple columnar epithelium
Basic plan of the gut wall layers (illustrated by esophagus)
Stratified squamous nonkeritanized epithelium (to resist abrasion)
Muscularis mucosa (express lymph and fluid from the fluid in the lamina propria) - contains fenestrated blood vessels, the most permeable in the body.
Muscularis externa: Inner circulate & outer longitudinal
Upper esophagus - Muscularis externa
Middle esophagus - Muscularis externa
Mix of striated and smooth
Lower esophagus - Muscularis externa
Regions of the stomach
Lower esophageal sphincter
Also split into Orad and Caudad region, about halfway through the body.
Rises above the entrance of the esophagus.
Contains air very often.
Large region into which food is delivered.
Separated from duodenum by pyloric sphincter.
Oxyntic region of the stomach
Corpus + Fundus
Contains parietal cells
Contains chief cells
Make Intrinsic Factor
The one component made by stomach completely vital for health.
Need it to digest Vitamin B12. Without IF, you get pernicious anemia and demyelination of the spinal cord. B12 deficiency.
Makes mucus pepsinogen
Contains G cells
Contains Mucous cells
Stimulates the production of more HCl.
Stimulates growth of gastric mucosa
Produced in pyloric region of the stomach.
Provides protection of mucosa from HCl
Produce gastrin if stimulated by alkaline environment or nerve activation.
Produce mucous pepsinogen
Cells in the stomach
Surface mucous epithelial cells
Mucous neck cells
Surface Mucous Cells
Superficial lining of surface and beginning of the pit area of the gland
Defend stomach against HCl
Mucous neck cell
Stem cells to regenerate lost surface cells
Abundant surface area when secreting
Contains intracellular canaliculi & microvilli
Specialized for regulation of secreted protein
Huge number of zymogen granules
Scattered through the glands
Components of a gastric gland
Pit (SurfaceMucous Cells)
Neck (Parietal cells, Mucous Neck Cells, Stem Cells, Enteroendocrine cells)
Base (Chief Cells, Parietal Cells, Enteroendocrine Cells)
What do parietal cells store?
In the resting state, there are tons of small tubulovesicles.
These will become microvilli by exocytosis
What allows a parietal cell to secrete acid?
A H+/K+ pump!!
Trades hydrogen for potassium
Funded by ATP hydrolysis
Cl- exits through channels in luminal membrane. Meets up with H+ and forms HCl in the lumen.
Bicarb is made as a byproduct of reverse-combusting water and CO2. This bicarb exits into the interstitial space in exchange for Cl-.
Once HCl is secreted by a parietal cell, what pH changes occur where?
Lumen is acidic
Blood is alkaline
Digestion - YAYYYY
CNS - sleepyyyyyy
What effects does stimulation of a parietal cell have?
Adds membrane and H+/K+ ATPase to the parietal cell surface.
What is needed for the conversion of pepsinogen to pepsin?!
Once some is converted, though, Pepsin can catalyse other pepsinogen, so it quickly becomes autocatalytic.
What happens to pepsin in an alkaline environment (Like in the duodenum)?!
It is irreversibly inactivated once it hits a pH > 3.5!!
Secrete into the lamina propria
Secretion granules are basolateral, not apical
Respond to luminal, neural or endocrine signals
Golgi lies between nucleus and base of cell
Few to no apical granules
Microvilli may be sensory
Involved in endocrine, paracrine and neurocrine signaling
Promotes gall bladder contraction.
Promotes secretion of pancreatic enzymes
Delays gastric emptying
Trophic to pancreas and gall bladder.
First hormone ever discovered
Promotes bicarb secretion from the pancreas, helps deal with the acid
Glucose-dependent Insolinotropic Peptide (GIP)
Promotes insulin release
Opposes insulin and promotes glycogenolysis