Bending structure and joint function part

A bending structure being bendable with respect to an axial direction, comprising:

• an outer coiled part formed of a wire which is wound in a coiled shape to have a plurality of coils in the axial direction;
• and
• an inner coiled part formed of a wire which is wound in a coiled shape to have a plurality of coils in the axial direction and arranged in the outer coiled part;
• and
• a flexible member extending inside the inner coiled part in the axial direction and movable in the axial direction to conduct operation, wherein
• the outer coiled part has a plurality of gaps to distance adjacent coils in the axial direction,
• the coils of the inner coiled part are provided so as to correspond to the gaps of the outer coiled part and fit between the adjacent coils while being in contact with the adjacent coils of the outer coiled part,
• the inner coiled part has a passing portion defined by an inner circumference of the inner coiled part, the inner circumference directly facing an outer circumference of the flexible member in a diametral direction, and the passing portion movably passing and guiding the flexible member in the axial direction so that the bending structure movably passes the flexible member through the passing portion in the axial direction and is bendable as well as the flexible member, and
• the flexible member has flexibility that allows the flexible member to axially move in the passing portion in a bending state of the inner and the outer coiled parts of the bending structure while keeping a bending posture of the inner and the outer coiled parts in said bending state without change.