Small animal GI Learning objectives (1: conc GI dz; 2: Clin apprch to GI dz; 3: Pre, Pro, Symbiotics) Flashcards
three basic gastric functions
- Gastric filling (adjustable food reservoir)
- Mix food with gastric secretions to start digestion
- gradually empty partially digested food into intestine
Accomodation
stomach adjusts size to inc volume w/o inc gastric pressure
accomodation is mediated by
vagal inhibitory fibers
Receptive relaxation
- when a bolus of food enters stomach
- vagal inhibitory fibers dec the lower esophageal sphincter pressure and fundic contractions
Disruption of gastric filling
- by failure to relax
- inflammatory dz
- neoplastic dz
Receptacle for food
Fundus
Distal pump
Anterum
Disruption of gastric emptying
vomiting
In dogs, when does the stomach empty
12-24 hours after eating
Final determinant of gastric emptying
caloric content of the meal
Structural components of gastric mucosal barrier
- surface mucus
- bicarb secreted
- epithelial cell membranes
- gastric mucosal blood flow
- prostaglandins and cytoprotection
- basal membrane
Secretion of gastric juice is not
continuous
Acid is secreted by
parietal cells
the making of bicarb
- each molecule of H+ secreted makes a molecule of CO2.
- CO2 combines with water to make bicarb
- bicarb goes into interstitial fluid
- mucosal capillaries in interstitium absorbs bicarb
Damage to gastric mucosal barrier
- allows H+ to leak back into the mucosa
- saturates buffers and cell pH decreases: cell injury/death
Result of damage to gastric mucosal barrier
- local ischemia
- hypoxia
- vascular stasis
- leakage of plasma proteins and blood into lumen
Vomiting reflex is mediated through
emetic center in medulla
Activation of the emetic center
- from higher centers
- from cerebellum
- from viscera
- from extra visceral sources
- drugs or toxins
Causes for activation from higher emetic centers
- CNS tumor
- limbic epilepsy
- inc crania pressure….
- others
Causes for activation of nausea from cerebellum
- motion sickness
- vestibular dz
causes for activation of nausea from viscera
- GI distention
- Torsions
- severe pain in viscera
- inflammation
Causes for activation of nausea from extra-visceral sources
- tonsillitis
- heartworms
- tactile stimulation of pharynx
Causes for activation of nausea from drugs or toxins
- Apomorphine
- Uremic toxins
- Hepatotoxins
- Endotoxins
- Cardiac glycosides
Emetic center can be directly stimulated by
- cerebral cortex
- chemoreceptor trigger zone
- oculovestibular system (cats only)
- GI tract
Chemoreceptor trigger zone
- located outside blood brain barrier so it can ‘sample’ chemicals in blood w/o it getting to brain
- this area is usually responsible for repeat vomiting
CRTZ is directly stimulated by
- emetic toxins
- the oculo vestibular system of dogs only
Diarrhea def
inc fecal water content which results in change of frequency, fluidity, and volume of bowel movements
Percent of fluid in intestines that come from diet
- 20%
- remainder comes from endogenous GI secretions
More fluid exchanged each day in GI than
there is in extracellular volume