Human digestive system is located in the upper right quadrant of the abdomen and below the diaphragm to which it is attached at one part, This is to the right of the stomach and it overlies the gall bladder. The liver produces bile, an important alkaline compound which aids digestion. Bile produced by the liver is made up of water (97%), bile salts, mucus and pigments, 1% fats and inorganic salts. Bilirubin is its major pigment. Bile acts partly as a surfactant which lowers the surface tension between either two liquids or a solid and a liquid and helps to emulsify the fats
Surface tension entropy, energy and free energy. As stated above, the mechanical work needed to increase a surface area "A" is . Hence at constant temperature and pressure, surface tension equals Gibbs free energy per surface area: where is Gibbs free energy and is the area. Thermodynamics requires that all spontaneous changes of state are accompanied by a decrease in Gibbs free energy. From this it is easy to understand why decreasing the surface area of a mass of liquid is always spontaneous (), provided it is not coupled to any other energy changes. It follows that in order to increase surface