GI Flashcards
layers of the gut wall, from inner to outer
lumen
- mucosa
- submucosa
- musclaris externa (circular then longitudinal)
- serosa
layers of the mucosa, from inner to outer
epithelium (specialized)
lamina propria
muscularis mucosae
2 nerve plexuses in GI mucosa (enteric nervous system) and where they are located
submucosal plexus- in submucosa
myenteric plexus- between two muscle layers
unit of absorption
villus
how is the salivary system regulated? what about the rest of the GI tract?
- saliva: only neural
- all others: neural, paracrine, endocrine
5 motility patterns
- segmentation (mixing, breaking down)- SI
- peristalsis (movement of food)- SI
- reverse peristalsis- vomiting - SI?
- MMC- between meals, stimulated by motilin between meals
- mass movement (moving fecal matter)- colon
functions of saliva & key enzymes
lubrication
protection
initial digestion - not major
- alpha amylase- starches
- lingual lipase- lipids
- lysozyme- maintains oral hygiene
final saliva is hypo/iso/hypertonic to plasma; it was initially hypo/iso/hypertonic ; at what flow rate is it most similar to plasma
final= hypotonic (ALWAYS); initially= isotonic
most similar to plasma at high flow rates
what are the net processes involved in saliva creation? which one is abnormal?
secrete K+, HCO3-
absorb Na+, Cl-
- HCO3- stimulated by parasympathetics, increases with flow rate
describe regulation of saliva secretion - stimulating and inhibiting factors
both result in saliva secretion!
1) parasympathetic (dominant)- releases Ach via CN 7&9 onto muscarininc receptors, Ip3/Ca2+ blocked by atropine
stimulating: conditioning, food, nausea, smell
inhibiting: dehydration, fear, sleep
2) sympathetic- T1-T3, Ne on beta-adrenergics, cAMP
3 phases of swallowing reflex, which is voluntary
1) oral - voluntary
2) pharyngeal
what is receptive relaxation?
LES and orad stomach relax at the same time
roles of the UES and LES, and which one is important for GERD
1) UES- protects airway- keeps food/acid out of airway, keeps air out of esophagus
2) LES- keeps acid out of esophagus - GERD
what does chronic gastric reflux cause?
change in esophageal mucosa from stratified squamous epithelium
1) to simple columnar (like in stomach) - just metaplasia
2) to simple columnar with goblet cells- barretts esophagus/intestinal metaplasia
what is the essential factor the the stomach secretes?
intrinsic factor, required for vitamin B12 absorption, don’t produce anywhere else
6 secretory cells of stomach
1) parietal/oxyntic- HCl, Intrinsic factor
2) mucous neck cells- mucus
3) peptic/chief cells- pepsinogens
4) enterochromaffin-like cells (ECLs)- histamine
5) D cells- somatostatin
6) G cells- gastrin
where are goblet cells located? where are cholangiocytes located?
goblet: intestinal, mostly large intestine
cholangiocytes: lining the bile duct
where does a proton pump inhibitor such as omeprazole work? what is lacking when you give this drug?
H+/K+ ATPase on luminal side
see no somatostatin b/c it only responds to low pH, have high levels of gastrin in their blood
what is the net result of gastric acid secretion?
net secretion: HCl
net absorption: bicarb
what protects the stomach from ulcers (what causes damage)?
- damage caused by H+/pepsins
- pepsin only works in low pH
- thick layer of mucus with bicarb trapped inside