GI - Intro Flashcards
gut fxn
acquire fuel to make ATP
get water
get electrolytes
get raw materials for construction
gut processes
movement
secretion
digestion
absorption
gut regulated processes
movement
secretion
GI SM RMP
slow waves
frequency diff in diff areas (3 - stomach, 12 - duo, 8 - colon)
interstitial cells of cajal (ICC) location
between long and circular muscle layers
interstitial cells of cajal (ICC) fxn
nonneural pacemakers from stomach and intestine
slow wave RMP benefits
synchronize muscle contractions (contractions only occur at crests)
peristalsis steps
- bolus distends gut
- stretch stimulates interneurons - inhibit (relax) downstream - excite (contract) upstream
- MP becomes more depolarized
- AP happens as slow wave hits (crest)
mucosa
innermost layer of GI tube
specialized along length
layers of mucosa
mucous membrane
lamina propria
muscularis mucosa
mucous membrane fxn
protective surface
secretion
absorption
mucous membrane cell type
epithelium
lamina propria cell types
CT small blood vessels lymph vessels nerve fibers MALT (immune)
muscularis mucosa cell type
SM
muscularis mucosa fxn
change folding to inscrease SA exposed to lumen
submucosa cell types
CT
larger blood vessels
submucosal (meissner’s) plexus
muscularis externa layers
inner circular muscle
myenteric (Auerbach’s) plexus
outer longitudinal muscle
outer longitudinal muscle fxn
shorten
inner circular muscle fxn
lengthen
myenteric (Aurbach’s) plexus location
between inner circular muscle and outer longitudinal muscle
serosa fxns
secrete fluid - make slippery
attach to body wall (mesentery)
mesentery fxns
suspend organs from inner wall like sling
adhesions inhibit mvmt
GI innervated by
ANS (extrinsic)
enteric nervous system (ENS - intrinsic)
ANS stim (para vs symp)
Para - stim motor and secretory activity
Symp - inhibit GI secretion and motility; constrict blood vessels
ENS components
myenteric plexus
submucous plexus
myenteric plexus fxn
exert control over motility
submucous plexus fxn
sense lumen environment
regulate GI blood flow
control epi fxn (secretion)
excitatory (contraction) GI NTs
ACh
Sub P
inhibitory (relaxation) GI NTs
NO
VIP
ATP
sensory NTs
serotonin (5-HT)
saliva fxns
lubrication of food prevent food apiration initiating digestion neutralize gastric acid minimize tooth decay
saliva: digestion
alpha amylase (cleaves 1,4-glycosidic bonds in starch) lingual lipase
saliva: antibacterials
IgA, lysozome, lactoferrin
lysozyme fxn
attack bacterial cell wall
lactoferrin fxn
chelates iron that micro-org needs for growth
salivary secretion cells
acinar cells
duct cells
acinar cells fxn
secrete initial salica
water, electrolytes and organic molecules (amylase)
resemble plasma in ion concentration/tonicity
myoepithelial cells
contract to secrete saliva
acinar transport (lumen side)
- K into lumen
- Cl/HCO3 cotransport into lumen
- Na comes into lumen paracellularly
acinar tranport (blood side)
- Na/K ATPase maintain Na gradient (Na into blood, K into cell)
- Cl/K/Na cotransport from blood to cell
salivary duct cell fxns
make modifications
reabsorb Na and Cl
add K and HCO3
saliva becomes hypotonic (remove more ions than add)
hormone that accentuates duct cell action
aldosterone
salivary secretion regulation (type)
neural only (aldosterone only modifies saliva)
salivary secretion regulation (parasympathetic)
major controller
stimulates salivary secretion
stimulates myoepithelial cells
vasodilation in surrounding blood vessels
salivary secretion regulation (sympathetic)
constrict blood flow
similar effects of para but transient, less pronounced
salivary secretion (para) mechanism
Ach
muscarinic cholinergic receptors
IP3 and increased Ca
salivary secretion (symp) mechanism
NE
beta receptors
cAMP
things that increase salivary secretion
food (sight, smell, taste, thought, chewing, spicy/sour tasting)
vomiting
smoking
things that decrease salivary secretion
sleep
fear
dehydration
fatigue
medical events that alter saliva composition
sjogrens
CF
post-radiation of head/neck
age changes to oral cavity
less saliva
taste bud atrophy
esophagus fxns
transfer food to stomach
isolate GI tract from outside
prevent reflux of gastric contents
esophagus musculature
upper 1/3 - skeletal
lower 2/3 - SM
esophagus layers
mucosa
submucosa
muscularis
serosa
esophageal sphincters (+ control)
upper - under voluntary control (contains sk muscle)
lower - regulated by ANS/ENS
GI tone
SM in GI walls maintains constant level of contraction
fxn of GI tone
keep P on contents
prevent overextension
types of digestive motility
propulsive movements
mixing movements
propulsive movements
propel contents at various speeds (eso: fast, SI: slow)
mixing movements
mix w/ digestive juices
expose contents to absorptive surfaces
pressure in pharynx leads to
pressure receptors send impulses to swallowing center (in medulla) which initiates the swallowing reflex@ pharynx and upper esophagus
how food stays out of nasopharynx
movement of soft palate + contraction of superior constrictors
contraction of superior constrictors –> ?
initiate peristaltic wave
actions of pharyngeal phase
close nasopharynx
propel food down into esophagus
UES relaxes
peristaltic wave
time in pharyngeal phase
< 1 second
time in esophageal phase
5 - 10 seconds
actions of esophageal phase
bolus passes through UES, sphincter constricts
primary peristalsis goes down esophagus
LES relaxes early
secondary peristalsis may occur to remove residual material
esophageal musculature innervation
vagus nerve
striated: somatic motor fibers of vagus
smooth: visceral motor fibers of vagus (to myenteric plexus)
LES actions
maintains tonic closure
augmented reflex closure
relaxes upon swallowing
LES innervations
tonic closure: myogenic/neurogenic factors
relaxation: vagally mediated inhibition (NO)
achalasia
LES fails to relax
difficulty swallowing
possible aspiration
achalasia mechanism
neuronal loss in myenteric plexus b/c myenteric fibrosis
particularly NO/VIP neurons
age changes to esophagus
stiffer muscle deterioration slower, weaker peristalsis less resting P of LES higher chance of reflux
