A freshly baked apple pie has just come out of the oven. Before you even saw it, the aroma of pie filled your house. The sweet scent of bubbling Honeycrisp apples mixed with the tangy smell of Grannysmith draws you into the kitchen. The pie is too hot to touch, so just stand there and stare at it. You watch as the sweet syrup from the apples drips down the sides of the pie. You can't take your eyes off the golden pie crust bursting with apples. The pie seems to be calling to you: “Come here. Come taste me, just one bite. » Is your mouth already watering? Before you even take a bite of food, your digestive system springs into action. Just the sight or smell, even a tantalizing description, of a delicious food is enough to make you salivate and produce stomach acids. Your digestive system is made up of the gastrointestinal (GI) tract, also called the digestive tract, and the liver, pancreas, and gallbladder. The gastrointestinal tract is a series of hollow organs united in a long tube running from the mouth to the anus. The main purpose of the digestive system is to break food down into smaller substances that your body can use for energy. After you take your first bite of pie, chemical digestion begins in your mouth. The salivary glands here produce enough digestive juices (saliva) to begin chemically breaking down food. Saliva moistens food and helps you chew, taste and swallow. In addition to the salivary glands located in the lining of your mouth, you have three pairs of larger salivary glands: the parotid, sublingual, and submandibular glands. Together, they produce 2 to 4 liters of saliva per day. The basic secretory units of the salivary glands are clusters of cells called acini. These cells secrete a liquid which in the middle of the paper acts and relaxes to mix and digest the food. The respiratory and digestive systems work closely together to produce energy. The respiratory system provides the oxygen needed for energy production and the digestive system obtains the nutrients needed for energy production. The digestive system has the closest relationship with the circulatory system. As the digestive system breaks down food, it absorbs nutrients into the bloodstream. The circulatory system then transports the nutrients obtained through the digestive system to the rest of the body. In a more obscure way, the nervous system, more precisely the marrow, controls all involuntary actions carried out throughout the digestive process. Finally, the endocrine system releases many hormones that affect the digestive process. These hormones determine when certain enzymes should be used and when certain nutrients should be absorbed...