L18: intro to GI function Flashcards
what are the 3 sphincteres of the GI tract
- lower esophageal sphincter
- pylorus
- ileo-cecal sphincter
what has failed to fuse in cleft palate
the opening between the oral and nasal cavity
stenosis and atresia of the intestine is a _______ malformation; caused by what during embryonic development
congenital
inadquate blood supply - leads to atrophy of affected portion
what layers make up the mucosa of the wall of the GI tract
epithelium
lamina propria
muscularis mucosa
what are the muscle layers that are in the wall of the GI tract
inner circular muscle
outer longitudinal
what plexuses make up the enteric NS of th GI tract
submucosal plexus + myenteric plexus
what type of epithelium is in the esophagus
multilayered stratified squamous
what type of epithelium is in the stomach, small and large intestine
columnar single layer
the small and large intestine epithelium is arranged in what way and for what purpose
LI: crypts
SI: crypts + villi
arrangement is for surface amplification
where do stem cells originate
neck area of crypts
what is the benefit to the constant renewal of the GI tracts epithelial layer
helps prevent accumulation of defects
neurons of the intrinsic nervous system (ENS) are located where
between an inner circular and outer longitudinal layer of muscularis externa (myenteric, Auerbach’s plexus) and within the submucosa (submucosal, Meissner’s plexus)
what do the neurons within the Myenteric plexus innervate
the longitudinal and circular smooth muscle layers; primarily - control of gut movement
what do the neurons of the submucosal plexus innervate
- glandular epithelium
- intestinal endocrine cells
- submucosal blood vessels
primarily - control of intestinal secretion
NTs of the enteric nervous system are released from ?
structures of the axons and axon collaterals called varicosites
what is the advantage of varicosites in the ENS
they are able to innervate a larger area
what are the excitatory NTs of the ENS
ACh and substance P
what are the inhibitory NTs of the ENS
Nitric oxide
Vasoactive intestinal peptide (VIP)
what is the function of the motor neurons on the ENS
innervate muscles and sphincters and cause contraction and or relaxation
what do the sensory neurons of the ENS detect
detect luminal pH, temperature and pressure
what are interstitial cells of Cajal (ICC)
specialized smooth muscle cells
- act as pacemakers to modulate contractile activity
- they have long processes that for gap junction with the longitudinal and circular sm cells
- self generating depolarizing rhythm that generate regular oscillations in the membrane potentia = slow waves
what is resposible for generating the slow waves of the GI tract
Interstitial cells of Cajal
what nerve is associated with the SNS of the GI
splanchnic
what nerve is associated w/ the PNS of the GI
vagus
what molecules are associated with sympathetics of the ENS and what effects do they have
NO and VIP
they decrease motility and secretions and increase sphincters
what molecules are associated with parasympathetics of the ENS and what effects do they have
Ach and substance P
they increase motility and secretions and decrease sphincters
what is the effect of NE on motility and secretions
decrease
what is the effect of Ach on motility secretions and gut blood flow
increases
what is a vagotomy
one of more branches of the vagus nerve are cut to reduce the rate of gastric secretions nad motility
enteroendocrine cells release what from their basal side into circulation or interstitium
- hormones
- neuroactive substances
- paracrine
- autocrines
what does the apical side of enteroendocrine cells do
sense gut content
endocrine secretions reach their target tissue via?
blood
paracrine secretions reach their target tissue via?
diffusion through the interstitial space
autocrine secretions of the paracrine cell modify the functions of ..?
the same cell
hence auto
enteric neurons secrete contents via _______ from _______
vesicles
varicosites
what hormones are produced by enteroendocrine cells
gastrin, secretin, CCK, GIP and motilin
where are intrinsic endocrine neuroactive substances (NO, substance P, VIP, enkephalines) released
near afferent nerve terminals into the underlying lamina propria
what does aldosterone do
stimulates water and sodium reabsorption in the colon by increases the amount of ENaC sodium channels
also increases reabsorption in salivary glands
what is the only hormone secreted outside of the GI tract that has controlling function
aldosterone
what do glucocorticoids do
increase the activity of the Na/K ATPase
