GI 3 Flashcards
Cephalic phase
Increased parasympathetic output from medulla to salivary glands and the ENS
Mechanical digestion
- chewing by teeth
- tongue and lips help
- joined by flood of saliva
3 pairs of salivary glands
parotid, submandibular, sublingual
4 functions of saliva
- soften and moisten food
- digestion of carbs (amylase)
- dissolve foods (taste)
- defense (lysozyme)
Saliva is an exocrine secretions which means…
It is released onto epithelium instead of bloodstream
How much saliva is ?released? per day?
1.5L/day
Saliva is __% water and __% solutes
99.5% water, 0.5% solutes
acini
secretory cells found in clusters
parotid glands
watery solution with amylase
submandibular glands
similar to parotid plus some mucus
sublingual glands
mainly mucus
Saliva secretion is primarily under _________ control.
parasympathetic
serous cells
secrete watery fluids; no mucus really
deglutition
reflex that pushes a bolus of food or liquid into the esophagus
somatic motor outputs
to pharynx and upper esophagus
autonomic motor outputs
to the lower esophagus
Explain process of swallowing
- soft palate elevates and closes nasopharynx
- larynx moves up and forward, closing trachea
- upper esophageal sphincter opens
Food moving downward into the esophagus is propelled by…and aided by…
peristaltic waves, gravity
epiglottis
helps keep swallowed material out of airways
gastroesophageal reflux disease (heartburn)
-negative intrapleural pressure during inspiration can cause esophagus to expand, drawing gastric acid and pepsin from the stomach
3 general functions of stomach
-storage, digestion, defense
receptive relaxation
upon swallowing food, parasympathetic neurons to ENS cause funds to relax
propulsion
moving chyme towards pylorus
retropulsion
when chyme is moved back to the body (from duodenum to stomach)
G cells
release gastrin in response to amino acids, peptides, and distension during short reflex
ENS and gastrin production
ENS stimulates gastrin production during long reflex
G-cells
stimulate gastric acid secretion
direct vs indirect gastric acid secretion secretion
direct: directly from parietal cells
indirect: stimulates histamine release from enterochromaffin-like cells, stimulating parietal cells
parietal cells
produce 1-3L of historic acid (HCl) daily with a pH as low as 1
gastric acid functions
- stimulate release of pepsinogen and cleaves it to pepsin
- denatures proteins
- kills bacteria and other microorganisms
- inactivates amylase from saliva
- stimulate D cells
pepsin
digests proteins
