stomach,liver,and intestines
After food is swallowed it travels in soft lumps down the gullet into the stomach. This stretches as it fills,to hold 2 litres(3.5 pt) or more.The stomach is both food mixer and acid-and-enzyme bath.Every few minutes its strong,muscular walls undergo a spasm of squeezing to churn the food into a semiliquid called chyme.Only a few substances are actually absorbed through the stomach lining into the blood.The next stage of the digestive tube is the small intestine,where chemical digestion continues and most nutrient are absorbed.Inside a healthy intestine live "friendly"bacteria.They can make important nutrients such as vitamin K,help to break down thick cellulose walls of plant cells,and are involved in processing bile salts.Both members of this partnership benefit-the bacteria have a warm,food-rich place to live,and the body obtains nutrients it would otherwise miss.The large intestine forms the leftovers into brownish,semisolid masses,ready for disposal.