Gastrointestinal Physiology Flashcards
where are the longitudinal muscles?
- outer layer of guts, contract linearly
where are the circular muscles?
- inner layer of guts, sphincter muscles that contract and make lumen smaller, contract circularly creating peristalsis
what is motility?
- movement of the gut wall
what is propulsive motility?
- moving aboral (away from mouth)
what is retentive motility?
- material is retained longer
what is mixing motility?
- material within lumen is churned
what is transit time?
- timing of material getting from one area to another
- altering transit time (increasing retention) and reducing propulsive motility are basis of treatments for d+
what is digestion?
- a reduction in size
- aim to reduce food to molecules small enough to be absorbed
what processes does digestion use?
- physical, chemical, and/or enzymatic breakdown
what is an example of a short transit time?
- birds eating high energy dense food - berries, little digestion is necessary - rapid absorption
what is an example of long transit time?
- ruminants can take 30+ hours for a food item to transit entire GI
what is mechanical digestion?
- physical dec in size caused by mechanical action
- mastication or by tearing foods into smaller pieces, not all species chew (reptiles, birds, snakes, lizards, etc.)
- gastric digestion: physical breakdown through contractions and mixing
what is chemical digestion?
- hydrolysis of chemical bonds by action of HCl
what is enzymatic digestion?
- hydrolysis of chemical bonds via enzymes produced by various regions of alimentary track or by hosted microbes
what is saliva?
- aids in mastication and deglutition
- volume varies but greatest in herbivores
what is special about ruminant saliva?
- buffered solution required to help support rumen microbes and buffer acid produced in fermentation process
- antifoaming characteristics
- flow continuous but varies with activity
- 80% of water entering ruminant stomach is via salivary secretions, beed water recovery from large intestine
what is amylase?
- in all species the major digestive enzyme
what is absorption?
- transport of nutrient particles into vascular system
- can only follow adequate digestion (size reduction)
what controls govern digestion and absorption processes?
- maldigestive disease share clinical signs with malabsorptive diseases
- etiologies are distinct and thus treated differently
- 2 very skinny dogs, one may have bad teeth (maldigestive), vs a skinny animal with history of parvo where absorptive lining destroyed (malabsorptive)
what is elimination?
- production, temporary storage, and expulsion of fecal mass
what is detoxification?
- the liver is integral in detoxifying many substances
what must all species do in order to manage bacteria?
- prevent bacteria from leaving gut and entering blood
- maintain correct types of bacteria for that species
- keep colonic bacteria out of small intestine
what are the two systems that control GI function?
- intrinsic
- extrinsic
what part of the nervous system controls intrinsic system?
- enteric nervous system
describe the enteric nervous system
- component of autonomic nervous system associated with regulation of digestion
- controls majority of GI functions independent of CNS
what do the intrinsic hormones do?
- hormones that regulate system, they do not digest and are not secreted into lumen as digestive compounds
what is the only extrinsic gut hormone?
- aldosterone
what does aldosterone do?
- helps regulate water absorption from GI tract
what nerves control extrinsic gut?
- vagus
- pelvic
- splanchnic
- hypogastric
what are the two forms of immune protection in GI?
- Peyer’s patches
- Paneth cells
what are Peyer’s patches?
- immune surveillance of of intestinal lumen. facilitate immune response within mucosal lining of gut, very prevalent in ileum
what are Paneth cells?
- secrete antimicrobial peptides and proteins among other things
what does gut lining secrete to aid in digestion and absorption?
- mucus, HCl, HCO3, enzymes, electrolytes, water, hormones
what is the first phase of digestion?
- luminal phase: takes place within lumen of GI tract
