L29 - Digestion 2 Flashcards
What occurs during the cephalic phase?
digestive reflexes triggered by stimuli are received in the medulla oblongata e.g. sight, sound, smell of food
feeds forward through to the PNS so that ENS activity is increased
Where does mechanical digestion begin?
in the mouth
What is mechanical digestion (mastication)?
chewing which involves slicing, tearing, grinding and mixing of food by the teeth
What is the role of saliva?
softens and lubricates food, mucus provides lubrication, lysozyme destroys bacteria
What is chemical digestion?
amylase activity which begins carbohydrate digestion
some lipase activity which begins fat digestion
What occurs during swallowing?
respiration is inhibited, the glottis and epiglottis close, the upper esophageal sphincter opens and the lower esophageal sphincter relaxes
What is the swallowing reflex?
- tongue pushes bolus against soft palate and back of mouth, triggering swallowing reflex 2. upper esophageal sphincter relaxes while epiglottis closes to keep swallowed material out of the airways 3. food moves downward
What propels food down the esophagus?
propelled by peristaltic waves and aided by gravity
What enables peristalsis to occur?
esophageal intraluminal pressures at different sites during swallowing
after a swallow, the “pressure wave” moves sequentially down the esophagus
Our gastroesophageal sphincter is normally closed to prevent…
gastric contents from refluxing into the esophagus
What is the role of the gastroesophageal sphincter?
separates esophagus from stomach, prevents reflux of stomach contents, relaxes to allow entry of food
What are characteristics of gastroesophageal sphincter disorders?
failure of relaxation: swallowing difficulties
ineffectiveness: reflux esophagitis “heartburn”
What are the three general functions of the stomach?
storage (and control of exit)
protection: acid environment destroys bacteria and other pathogens, stomach must also protect itself from “autodigestion”
digestion: enzymes, acid assists
How does the stomach digest?
mechanical: mixing (peristaltic waves)
chemical: enzymes, acid assists
absorption: no food, some water
What is going to increase the rate of emptying of stomach contents into the duodenum?
volume of chyme in the stomach