g.i tract - prof peters Flashcards
carries food and liquid from the mouth to the stomach propelled by ……….?
peristalis
the upper and lower part of the oesophagus are bounded by what?
upper and lower oesophageal sphincters
the oesophagus is lined by what cell type
stratified squamous epithelium
the oesophagus musculature contains, striated and smooth.
what regions of the oesophagus would you find these
striated - upper thrid
smooth - remainder
what nerve innervates the oesophagus
vagus nerve CNX
what triggers the closure of the upper oesophageal sphincter
once food has entered the oesophagus
primary peristaltic wave (vagus nerve)
swallowing centre (pons and medulla)
what is the enteric nervous system
its the nervous sytsem that governs the GI system
what do the circular fibres do behind bolus during peristalsis
contract to squeeze it down to stomach
what do longitudinal fibres infront of bolus do, during peristalsis
contract to shorten distance to travel
after swallowing how many seconds later does the lower oesophageal sphincter open
2-3 seconds
prevents reflux
when would a secondary peristaltic wave occur
when sticky food becomes lodged in the oesophagus
what digest protein in the stomach
pepsin and HCl
approximatley how much gastric juices is produced by the gastric glands
2 litre/day
mechanical activity occurs as two types. what are they
orad stomach
caudad stomach
for storage of ingested material in the stomach. must stomach relax or contract
relax via vagus nerve
would you expect to find greater wave activity in the orad or the caudad region
caudad region
where would you find thick musculature in the stomach
orad region or caudad region
caudad region
why is there minimal mixing of contents for long periods in the orad region
allows for carbohydrate partial digestion by salivary glands
what occurs during retropulsion
mixing of gastric contents, whilst reducing chyme to small particles, so that it passes through the pylorus
Strength of antral wave determines escape of chyme through pyloric sphincter
which is goverened by what
gastric factors
duodenal factors
what are the gastric factors that affect emptying of chyme
stretch of smooth muscle
stimulation of intrinsic nerve plexuses
increased vagus nerve activity and gastrin release
consistency of chyme
what stimuli in the duodenum affects gastric emptying
fat - duodenum needs to prepare
acid - pancrease needs to prepare
hypertoncity - osmotically active
distension
what is the gastric mucosa composed of
lining of stomach
pits, invaginations of the surface
glands, at the base of the pits
in which region of the stomach would you find an increase in parietal and chief cells.
oxyntic or plyoric
oxyntic area
which regions would you find d cells
pyloric or oxyntic
pyloric
functions of gastric secretions
HCl
activates pepsiongen to pepsin
denatures protein
kills most microorganisms
functions of gastric secretions
pepsinogen
inactive precursor of the peptidase
functions of gastric secretions
histamine
stimulates HCl secretion
functions of gastric secretions
Mucus
protective
(pyloric gland area and antrum)
functions of gastric secretions
gastrin
stimulates HCl secretion
functions of gastric secretions
somatostatin
inhibits HCl secretion
what are the three phases of gastric acid secretion
cephalic phase - in the head
gastric phase - when food is in stomach
intestinal phase - after food has left stomach
what are the three inhibition stages of gastric acid secretion
cephalic phase - vagal nerve activity decreases
gastric phase - ph falls as food exits stomach
intestinal phase - factors that reduce gastric motility, reduce gastric secretion
Drugs that reduce gastric acid secretion are used in the treatment of…
peptic ulcer
gastro-oesophageal reflux disease
acid hypersecretion
what drug acts as a proton pump inhibitor
omeprazole
what conditions need to be met for the success of omeprazole
timing of dosing
orally once daily
full effect achieved after repeated dosing
