We have all heard the saying "where form meets function." If we think of anatomy as being the form, then physiology is the function. The field of physiology can be broken down into numerous sub-categories like reproductive physiology, gastrointestinal physiology and renal physiology. Through an understanding of physiology, we can better understand what makes animals sick and how they can be made better. Physiologists also study when is the right time for animals to bred, what diet changes should be made during lactation and how does stress impact immune function.
In the video below, Paul Andersen, a high school science teacher from Bozeman, Montana does a nice job explaining the basic concepts behind anatomy and physiology.