A device for accessing tissue within a body lumen comprises an elongated body portion defining a lumen and an anchoring mechanism including an expanding structure on a distal portion of the elongated body portion. The anchoring mechanism moves the expanding structure from an insertion configuration in which the expanding structure is constricted against the device to an operative configuration in a body in which the expanding structure expands away from the device without altering a length of the anchoring mechanism in combination with a control mechanism for selectively engaging the anchoring mechanism.