Meal Phases: Cephalic + Oral + Esophageal Flashcards
function of cephalic phase
prepare the GI tract for a meal
mechanism of cephalic phase
olfactory/visual/auditory cues trigger anticipatory cognitive pathways –> increase parasympathetic output to GI tract
effect of cephalic phase
- increased salivary, gastric, and pancreatic secretions
- relaxation of proximal stomach
function of oral phase
mechanical disruption and initiation of digestion (chewing and swallowing)
mechanism of oral phase
increase parasympathetic output to GI tract
effect of oral phase
- increased salivary, gastric, and pancreatic secretions
- relaxation of proximal stomach
- contraction of gallbladder to release bile into SI - triggered by CCK
chewing
- involves muscles of mastication, tongue, cheeks
- increases surface area of ingested solids
- mixes solids with saliva to lubricate bolus
what part of CNS controls swallowing
deglutition center in brainstem
is swallowing voluntary or involuntary
starts voluntary then becomes involuntary
voluntary part of swallowing
controlled by CNS only
- tongue pushes bolus back into pharynx
- sensory nerves detect bolus and activate deglutition center
involuntary part of swallowing
controlled by CNS and ENS
- closing of nasopharynx
- closing of oropharynx
- epiglottis blocks laryngeal opening
- wave of muscular contractions pushes bolus to esophagus
- UES relaxes to allow food into esophagus
function of esophageal phase
transferring food from mouth to stomach
prevention of reflux
mechanism of esophageal phase
bolus distends esophagus –> triggers mechanosensitive afferents (vagal and intrinsic) –> signals to vagal and intrinsic efferents –> motor reflex causes primary peristalsis of esophagus –> distention after primary peristalsis triggers secondary peristalsis –> secondary waves repeat until bolus is passed
effect of esophageal phase
bolus reaches the stomach
salivary glands
tubuloalveolar structures that contain acinar epithelial cells
salivary gland ducts
contain duct cells
serous acinar cells
secrete digestive enzymes
histology: basal nuclei, rough ER, apical secretory granules
mucus acinar cells
secrete mucin
histology: large secretory granules
duct cells
secrete bicarbonate
function of saliva
- lubrication and moistening food
- solubilizing food for taste
- anti-bacterial
- clearance and neutralization of esophagus
- grooming/temp control
- starch digestion (NOT dogs)
components of saliva
electrolytes, bicarbonate, lipase, mucin, lysozyme, amylase
what regulates salivary secretions
autonomic nervous system
parasympathetic: active; more watery
sympathetic: passive; more viscous
primary salivary secretions
secretions from acinar cells (mucus, serous)
isotonic
secondary salivary secretions
secretions from duct cells to modify primary secretions
hypotonic
esophagus function
conveys food from pharynx to stomach
esophagus epithelium
stratified squamous non keratinized
esophagus lamina propria
no glands
diffuse lymphatic tissue
esophagus submucosa
mucous glands only
esophagus muscularis
dogs/ruminants: striated
cats/horses: proximal striated, distal smooth
longitudinal folds
aid in adjusting size of esophagus to pass larger boluses
