The Process of digestion

Stages of Digestion Determine the order which the events of digestion occur. Step 1 Once food enters the mouth, salivary glands produce saliva that contains amylase. Amylase begins the digestion of starch and carbohydrates. Step 2 From the mouth, food is pushed down the esophagus by swallowing. The food then passes through the cardiac sphincter into the stomach. The cardiac sphincter prevents the contents of the stomach from moving back up the esophagus. Step 3 Within the stomach, digestive glands within the lining of the stomach produce acid and pepsin to break down proteins. A thick layer of mucus is also released to protect the stomach from the acid. Step 4 The stomach is a muscular pouch that contracts and releases to “mix up” the food and digestive juices of the stomach much like a washing machine. Once the food is properly mixed, the stomach pushes the contents through the pyloric sphincter into the first part of the small intestine, called the duodenum. Step 5 The liver, pancreas, and gallbladder are attached to the duodenum through ducts and release additional digestive juices into the small intestine. These include bile to emulsify fats, amylase to further break down carbohydrates, lipase to break down lipids, and trypsin to further break down proteins. Step 6 As the contents travel through the small intestine, they are absorbed through small projections on the surface of the intestines called villi. Each villi is connected to a capillary so, as molecules diffuse through the villi, they are transferred directly into the blood stream to be taken to the cells of the body. Step 7 Eventually, any contents that are left and have not been absorbed by the small intestine are pushed through the ileocecal valve into the colon. Step 8 As the contents move through the colon, water is absorbed and the leftover contents become feces that are expelled through the rectum and anus during a bowel movement.