Abstract: A positioning aid includes an opening configured to be inserted a distal end portion of an endoscope; and an alignment portion configured to be aligned with a particular alignment subject on a distal end surface of the endoscope. The alignment portion is configured to line up with the particular alignment subject in a longitudinal direction of the endoscope in a state where the endoscope inserted into the opening and a guide sheath are arranged to have a particular positional relationship in a circumferential direction about a longitudinal axis of the endoscope.

Abstract: A medical sheath is a medical sheath to be used in combination with a medical device including an insertion portion that can be inserted into a body cavity of a subject via a trocar, the medical sheath including: a sheath body formed in a shape that can be inserted to and removed from a through hole through in the trocar; a channel provided in the sheath body, the channel having a shape that enables insertion and removal of the insertion portion; a first optical transmission section provided in the sheath body, the first optical transmission section being provided for guiding illuminating light; and a second optical transmission section that is provided in the sheath body and is separate from the first optical transmission section, the second optical transmission section being provided for guiding return light generated upon application of the illuminating light from the first optical transmission section.

Abstract: A medical device includes: an insertion portion formed in an elongated shape that can be inserted into an insertion hole of an insertion assisting instrument that assists insertion into a body cavity of a subject; a distal end portion that is provided in the insertion portion and is configured to be capable of emitting an illuminating light that is irradiated at the subject; and an interlock mechanism which has a member that is provided in the insertion portion, and which is configured to, in conjunction with a position between the insertion assisting instrument and the member, perform an operation for transitioning to either one of a state in which emission of the illuminating light by the distal end portion is possible and a state in which emission of the illuminating light by the distal end portion is not possible.