Introduction

Question 0

Outline the broad functions of the various regions of the GI tract

Answer 0

Mouth - initial physical disruption, starts digestion
Stomach - storage, initial disruption, disinfection
Small intestine - dilution and neutralisation of chyme, absorption
Large intestine - absorption, dehydration
Rectum - excretion

Question 1

Describe the overall processes of the GI tract

Answer 1

Digestion
Absorption
Excretion

Question 2

Describe the fluid balance of the gut

Answer 2

1kg of food + 1.5l saliva + 2.5l gastric secretions + 9l water and alkali
Small intestine absorbs 12.5l
Large intestine absorbs 1.35l
–> 150g faeces

Question 3

Describe the properties of the enteric nervous system, and its relationship to the autonomic nervous system

Answer 3

Subdivision of ANS
Two plexuses in wall of gut - short reflex, long reflex
Neural –> autonomic (parasympathetic –> secretion and motility, range of neurotransmitter
Paracrine –> histamine controls secretion of acid, vasoactive substances
Endocrine –> enzyme secretion, alkali secretion, secretion of stomach acid

Question 4

Describe the role of hormones and other peptides which affect the motility and secretion in the gut

Answer 4

Gastrin

Secretin