What Is The Role The Stomach Plays In The Digestive Tract?

It stores food for 3-4 hrs while digestion is occurring. The churning helps break down protein.

Most people believe that stomach is the only part of the digestive
system where food is collected and digested. Well, that is where the
food collects but that is not the only place where digestion occurs. In
the aspect of digestion, stomach has two important roles:

1. 
   It 'churns' the food by contractions of its wall muscles. This
   thoroughly mixes the food with all the enzymes in the stomach and also
   breaks down food particles into pieces small enough to be acted upon by
   enzymes. Thus, stomach is very important as far as 'physical digestion' goes. The only other place where this happens is the mouth where chewing breaks down food particles. When the stomach is done churning the food, the result is a liquidy mixture called 'chyme'.
2. The second important role of stomach in digestion is the digestion of protein. It has enzymes that digest proteins (proteases). These act on proteins to break them down into amino acids.
3. Stomach is also the place for absorption of some substances into blood like alcohol.