Intestinal contents are liquid when they reach the large intestine but
are normally solid by the time they reach the rectum as stool. The many
bacteria that inhabit the large intestine can further digest some material,
creating gas. Bacteria in the large intestine also make some important
substances, such as vitamin K, which plays important role in blood clotting.
These bacteria are necessary for healthy intestinal function, and some
diseases and antibiotics can upset the balance among the different types
of bacteria in the large intestine.
The large intestine does not undergo much change with age. Constipation
becomes more common. This may be due partly to a slight slowing in the
movement of contents through the large intestine and modest decrease in
the contractions of the rectum when filled with stool.
