The film starts with a cutaway of man's upper body.
Besides the brain, the only organs shown are
the mouth, throat, esophagus, and stomach.
Peristalsis is a series of wave-like muscle
contractions that move food through the digestive tract.
The man chews and swallows a ball of food
that bulges as it travels through the esophagus.
It starts in the esophagus
where strong wave-like motions of the smooth muscle
move balls of swallowed food to the stomach.
A box around the stomach enlarges to
show a cutaway of the top of the stomach.
Food enters in waves as the esophagus contracts.
There, the food is churned into a liquid
mixture called chyme that moves into
the small intestine where peristalsis continues.
The image changes to a close-up of the small intestine.
Then a section of intestine is enlarged and straightened.
Stretching out a piece of intestine
will make it easier to see the wave-like motion.
A cut away of the stretched intestine shows the inside wall.
As chyme passes through,
wave-like motions of the intestine shift it back and forth.
The motion mixes and shifts the chyme back and forth.
This lets the bloodstream absorb nutrients
through the walls of the small intestine.
A new image shows a close-up of the large intestine.
In the large intestine peristalsis helps water
from undigested food be absorbed into the blood stream.
Then, the remaining waste products are
excreted through the rectum and anus.