The idea of all physiological systems is to keep the body"s internal environment stable. The git is concerned with supplying the milieu interieure with the nutrients required to maintain balance. Large particles of food enter the oral cavity and are broken down mechanically and chemically. Until they are small enough to be absorbed and metabolized. Physiology concerns itself with how the body obtains the food. There are other levels, such as psychological control of hunger, and biochemical breakdown of molecules. We will consider the gastrointestinal tract and how it accomplishes the goal of getting nutrients to the body. The function and structure of the git are strongly related. Git connects 2 ends of the external environment through the body of the worm. This is shared with humans: we are tubes. Through evolution, 2 key differences have occurred from early git to human git. Human git are much longer and bigger than worm git.