This invention relates to a three dimensional bioengineered sphincter such as a bioengineered internal anal sphincter (IAS) and three-dimensional physiological models of smooth muscle cells. The invention also related to methods for generating a bioengineered sphincter and smooth muscle rings in culture. In addition, the invention provides for methods of using a bioengineered sphincter or bioengineered smooth muscle ring to identify agents that modify contractile force and relaxation in smooth muscle cells.