1. GI Part 1 Flashcards
List the functions of the GI system (5)
- transportation of food
- digestion of food in absorbable particles
- regulation of water and electrolyte balance
- immunologic barrier (GALT)
- thermoregulation – fluid intake, panting
general differences between different GI systems
carnivores
ruminants
horses
birds
carnivorous - big stomach, relatively short intestinal tract
ruminants - fermentation in forestomach system
horses - fermentation in the large intestine (hindgut)
birds - food storage in the crop, glandular stomach called proventriculus, muscular stomach called gizzard
species differences in prehension
horses cattle goats/sheep pigs carnivores
horse - lips (eating from manger), incisors (grazing)
cattle - tongue (wrap around forage), incisors
goats/sheep - tongue, lips
pigs - snout, mandible
carnivores - canines, incisors, forelimbs
define mastication
first act of digestion
involves actions of teeth, jaws, and tongue
describe carnivorous mastication
very sparsely, movement of mandible is vertical
molars and premolars in the upper and lower jaws move against each other like scissor blades
describe herbivorous mastication
spend long time masticating
upper and lower jaws are large providing room for teeth with large chewing surfaces
movements are horizontal
functions of GI tract movements (4)
- propel ingesta from one location to the next
- retain ingesta at a given site for digestion, absorption, or storage
- break food material physically and mix it with digestive secretions
- circulate ingesta so all portion come in contact with absorptive surfaces
what are the 2 phases of deglutition
Voluntary phase (oral phase) food is in the oral cavity and is molded into a bolus; using the tongue it will be pushed back into the pharynx
when the food enters the pharynx –> activation of sensory nerve endings –> initiation of involuntary phase
Involuntary phase (swallow reflex) occurs within the pharynx and esophagus --> directs food into digestive system (away from upper airways)
sequence of events of deglutition (4)
- soft palate elevated closing the pharyngeal opening of the nasopharynx preventing food from entering the internal openings of the nostrils
- tongue is pressed against the hard palate closing off the oral opening
- epiglottis is moved backwards covering the entrance of the trachea preventing the movement of food into the respiratory system
- upper esophageal sphincter opens and food transported through esophagus by peristaltic contractions; the entrance of the trachea is reopened and respiration continues
disorders of deglutition
Dysphagia - difficulty in swallowing due to neuromuscular disorder of mechanical obstruction
Oropharyngeal Dysphagia - malfunction of the pharynx and upper esophageal sphincter
Esophageal Dysphagia - malfunction of the esophagus
Aspiration - a dysphagia in which food particles/fluids or stomach contents (acid reflux) reach the upper airways
what is the regulatory center for energy homeostasis
hypothalamus
hunger center - Nucl. paraventricularis, lateral hypothalamus fields, perifornical region
satiety center - Nucl. ventromedialis
regulation of food intake - neuropeptides in the hypothalamus
stimulatory - neuropeptide Y (NPY), orexin
inhibitory - melanocyte stimulating hormone (MSH)
what does MSH do
inhibits hunger and increases energy consumption
regulation of food intake - non hypothalamic hormones
stimulatory - ghrelin
inhibitory - cholecystokinin (CCK), peptide YY (PYY), leptin, insulin
where is CCK produced and what does CCK do
produced by small intestine
inhibits food ingestion
released after a meal while food being digested in small intestine
