Endoscopes having a hollow outer sheath configured for insertion into a patient's body are disclosed. A hollow inner sheath is receivable within the outer sheath, and is configured to slideably receive a first internal instrument. A working element can be configured to rotatably support at least the first internal instrument and a second internal instrument such that at least the first internal instrument and the second internal instrument are rotatable about a common axis of rotation being substantially coextensive with a longitudinal axis of the outer sheath. The working element can have at least one guide rail extending longitudinally of the axis of rotation and an actuator block can be slideably mountable to the at least one guiderail and so securable to at least one of the instruments as to be able to urge the at least one of the internal instruments longitudinally of the outer sheath.