Our Gut Reactions To Food Flashcards
What happens in phase 1/oral phase of deglutition?
Food bolus is formed by mastication
Tongue moves up and backwards
VOLUNTARY
What happens in phase 2/pharyngeal phase of deglutition?
Soft palate rises Epiglottis closes Pharynx contracts UOS relaxes INVOLUNTARY
What happens in phase 3/oesophageal phase of deglutition?
UOS contracts
Bolus moved by peristalsis
LOS relaxes
What does the pharynx stimulate?
Tactile/distension receptors on pharynx send signals to brain stem which sends signals causing the UOS to relax
What happens when food enters the stomach?
Signals travel up vagal afferent fibre to brain stem
Brain acts to change gut environment by signals down vagal efferent fibres
Eg Ach down phrenic nerve
Reflex contractions of lower oesophageal sphincter
What are the regions of the stomach?
Lower oesophageal sphincter Fundus Corpus - acid secreting Antrum - muscular pump where endocrine cells lie Duodenum Pyloric sphincter
How is food mixed in the stomach?
Retropulsion
What keep food in the stomach?
Pyloric sphincter
What happens in the pacemaker zone of the stomach?
Peristaltic contractions
How do we accommodate a large meal?
Receptive relaxation of the body of the stomach (corpus)
Brainstem acts on intrinsic nerves in stomach wall, switches off nerves giving stomach tone and switches on nerves that relax
What is released when we have had enough food?
At the end of a meal CCK acts on vagal afferent fibres
Lowers appetite and lowers food intake
How do fatty meals delay gastric emptying?
By releasing CCK from the duodenum
What delays and controls gastric emptying?
Fat rich, hypertonic and acidic meals, and meals with high viscosity all delay gastric emptying
Rate of emptying is controlled by the duodenum
What is the major cell type in the fundus of the stomach?
Surface epithelial
What is the role of mucus in the fundus?
Contains Mucins which detects against proteases
Barrier against forces and mechanical damage
What is the role of HCO3 in stomach?
Creates a pH diffusion barrier
Protects against acid
What is the role of gastric lipase in fundus of stomach?
Facilitates the breakdown of fat