physiology of large intestine Flashcards
what happens in mechanical digestion in the large intestine
- chyme enters through the ileocaecal valve
- haustral churning
- peristalsis occurs slowly (mass movement)
what happens in chemical digestion in the large intestine
- only bacterial enzymes are present
- carbohydrates are fermented to produce flatus
- break down remaining amino acids
what is the predominant mixing in the large intestine
segmental contractions
how do mass movements work
intense and prolonged peristaltic contraction which can clear sections of the colon of all contents
are mass movements seen anywhere else in the digestive tract
no
what stimulates colonic motility
morning wakening
what does gastrocolic reflex cause
increased motility in colon in response to stretch in stomach and byproducts of digestion in the small intestine
what influences transit
diet - eg fibre increases faecal weight and reduces transit time
stress can increase motility
what does immobility lead to
constipation
how does age affect colonic motility
can prolong transit time
do women have slower or faster colonic transit time
women have slower transit time
how much water enters large intestine per day and how much is reabsorbed
0.5-1L and all except 100ml is reabsorbed
what does faeces consist of
- undigested food
- inorganic salts
- sloughed off epithelial cells
- bacterial products
- bacteria
what is in the ascending (right) colon
it is relatively fluid
has the consistency of muesli with large aggregates beginning to form
what is in the transverse colon
less water and some gas
what is there a risk of in the descending colon
risk of impaction in faeces
