GI Physiology 1 Flashcards
GI tract is a…
Tube! mouth to anus
Systems needed for food acquisition and ingestion
Sensory!
tactile, visual, olfactory, memory
and of course mechanical ingestion
Pre-gastric mechanical functions
prehension - seizing food in mouth
mastication
deglutition- swallowing
3 stages: mouth (voluntary), pharynx, esophagus (both reflex)
What is segmentation
back and forth mixing due to intermittent contraction of circular smooth muscle
(promotes digestion and absorption!)
What is peristalsis?
unidirectional waves of contraction towards the anus
(propulsive in nature)
Motility in the gut wall (3 types)
propulsive - moving aboral
retentive - material is retained longer
mixing - material within lumen is churned
timing of material from one area to another is called…
transit time
transit time ___ between species and diet
VARIES
minutes in small birds eating high energy dense food (rapid absorption)
30+ hours in ruminants - time needed for roughages and microbial environment
altering transit times?
increasing retention and reducing propulsive motility are the basis of treatments for diarrhea
digestion vs absorption
digestion = reduction in size
- reduce food to molecules to be absorbed
- physical, chemical, enzymatic breakdown
absorption = transport of nutrient particles into vascular system
- must follow digestion
chemical and enzymatic digestion
chem: hydrolysis of chemical bonds, by HCl
enzyme: hydrolysis of chemical bonds via enzymes
Saliva function and what species its greatest in?
aids mastication and deglutition
volume varies but is greatest in herbivores!
Ruminant saliva
buffering solution - support rumen microbes and buffer acid produced in fermentation process
antifoaming
continuous flow
80% of water in ruminant stomach is from salivary secretions
In all species the major digestive enzyme produced by the salivary glands is?
Amylase
maldigestive diseases share clinical signs with______ diseases
malabsorptive
etiologies are treated differently
(bad teeth = maldigestive, vs parvo pet where absorptive lining has been destroyed)
What is detoxification?
liver is integral in detoxifying substances
for bacterial housing; all species MUST (4)?
• Prevent bacteria from leaving the gut and entering the bloodstream
• Maintain the ‘correct’ types of bacteria for that species.
• Keep colonic bacteria out of small intestine
• Provide a good environment (be a good host) for fermentative bacteria.
2 systems control GI Function
extrinsic and intrinsic
both controlled by nerves and endocrine secretions
Intrinsic neuronal control in the enteric nervous system
autonomic system
-regulation of digestion
ENS controls GI functions independent of central nervous system
Intrinsic gut hormones
gastrin, gastric inhibitory peptide (GIP), cholecystokinin (CCK), secretin, and motilin.
not responsible for digesting
hormones made by_______ tract have both local and systemic influences because…
alimentary
they are secreted by the organ into systemic circulation
APUD cells are?
group of endocrine cells that (some) secrete hormones with GI function
Amine Precursor Uptake Decarboxylase
APUD cells in the GI are distributed______ and secrete different hormones based on ….
throughout!
where they are in the GI
Extrinsic nervous control is via the … (4 nerves)
Vagus nerve!! (parasympathetic)
pelvic nerve (parasympathetic)
Splanchnic nerve (sympathetic)
Hypogastric nerve (sympathetic)
Only extrinsic gut hormone is ______ which helps regulate water absorption from GI tract
aldosterone. !!!!!!!!!!
What are peyer’s patches
immune surveillance of the intestinal lumen. Facilitate the immune response within the mucosal lining of the gut. Especially prevalent in the ileum.
What are paneth cells
Secrete antimicrobial peptides and proteins, among other things.
Phases of assimilation of foodstuff
DIGESTION
1. luminal phase of digestion
2. Mucosal phase of digestion
3. Intracellular phase of digestion
ABSORPTION - 4. transport phase
Luminal phase of digestion
1st
lumen of GI tract (mouth to SI)
uses enzymes from organs and accessory glands and hosted microbes
Luminal phase produces
- Short-chain polymers, that are still too big to absorb into blood
- in the ruminant and equine: the symbiotic microbes produce some products of absorbable size
Mucosal phase of digestion
Only in SI
only on surface of enterocytes
made by enterocytes
enteric enzymes further digest products of luminal digestion
intracellular phase of digestion
(similar to mucosal phase)
only in SI
within enterocytes
important only for protein
CNS can_____ but not ____ the gut
influence, but not entirely control the gut
short reflexes
from gut back to gut
named from origin to destination
affect motility or secretion
long reflexes
gut to spinal cord back to gut
ex: vomiting and defecation (more complex)
What is the largest endocrine organ of the body?
the GI tract
2 dietary glucose-containing polysaccharides
starch and cellulose
starch= digestible
cellulose= 100% not digestible by vertebrates
cellulose is accessible via _____
fermentation - microbial flora
horses are ____ fermenters
hindgut - LI is modified to host microbes
ruminants are _____ fermenters
foregut
stomach modified to host microbes
foregut vs hindgut
The bacterial portion of the microflora contains large amounts of protein
In hindgut fermenters, the microbial mass is passed out of the body in the feces
In foregut fermenters, microbial mass is passed on into remainder of GI tract, digested, and utilized as a protein source
in short - fore= protein source, hind= waste
ecological differences in hindgut vs foregut fermentation
size limit to foregut fermentation (rumen takes up a lot of time and space in the body - requires balance)
-giraffe is the largest ruminant, elephants cannot be ruminants - the physics don’t work
Other variables
transplant - rumen bacteria transplant
forage quality
water recovery
cecal digestion
veterinary concerns-
• Drugs that kill the bacteria
• Drugs that get digested before being therapeutically absorbed
• Dietary imbalances that adversely affect the flora/fauna of the gut
