How to use: Press Feed a meal and the bolus waits in your mouth while
you chew — the clock does not start until the swallow carries it down. Chewing is not cosmetic,
it multiplies the surface area the enzymes can work on. Watch the pink bolus travel down by
peristalsis. The stomach is acid, so only pepsin
works there; the small intestine is neutralised by bicarbonate from the pancreas, which is when
amylase, trypsin and lipase get to act, while bile breaks fat into droplets so lipase has
something to grip. Watch for absorbed dots crossing the wall into the blood and lymph vessels.
Finally the colon reclaims water and you get the balance back. Turn peristalsis right up and
notice what happens to absorption; lower the stomach pH and watch salivary amylase die.
Notice: digestion is not one step, it is a schedule. Each enzyme only works inside a
narrow pH window, so the stomach's acid has to be switched off again by bicarbonate before the
next set can act — and a bolus that moves too fast simply passes enzymes by. Absorption depends
on two things you can see here: how much surface area chewing created, and how long the food
lingers against the villi. And not everything takes the same route: sugars and amino acids go
straight to the liver through the portal vein, but fats are packaged and sent down the lymphatic
duct first.