GI physiology Flashcards
besides mechanical ingestion, what systems are necessary to acquire and ingest food?
sensory
- tactile
- visual
- olfactory
- memory
prehension
seizing food and conveying it into the mouth
Mastication
mechanical breakdown of food in the mouth
chewing
deglutition
swallowing
3 stages:
- through the mouth (voluntary)
- through the pharynx (reflex)
- through esophagus (reflex)
segmentation
back and forth mixing due to intermittent contraction of circular smooth muscle
peristalsis
unidirectional (usually aboral) waves of contraction
propulsive motility
moving bolus aborally
retentive motility
material is retained longer
mixing motility
material in lumen is churned
digestive transit time
timing of getting material from one area to another
short in birds (less digestion of high energy berries)
long in ruminants (30+ hours)
digestion vs absorption
digestion is a reduction in size using physical, chemical, and enzymatic breakdown. Aim is to make molecules small enough to be absorbed.
Absorption: transport of nutrient particles into vascular system
mechanical digestion
simple decrease in size
mastication
gastric digestion through contractions, mixing
enzymatic digestion
hydrolysis of chemical bonds via enzymes produced by alimentary tract or bacteria
chemical digestion
hydrolysis of chemical bonds via HCl
mostly in stomach
ruminant saliva
buffered solution required to help support rumen microbes buffer acid produced in fermentation
antifoaming characteristics
flow is continuous but varies with activity