Embodiments of a surgical access port system that comprises a retractor that is adapted for being coupled to a cap and that is particularly useful in natural orifice surgery are described. The retractor comprises an outer ring, wherein the outer ring is configured to be disposed proximate the natural orifice of the patient and substantially surround the orifice; a tubular body; and various stabilizing mechanisms surrounding the tubular body, sized and configured to stabilize and retain the retractor within the orifice. The stabilizing embodiments described herein are useful in all natural orifices and are of particular use in the vaginal surgery.