An endoscope comprising: a tubular elongated member; a tensioning wire in a tensioning lumen along one side of the elongated member, between the proximal end and the distal end of the elongated member; a head arranged at the distal end of the elongated member and comprising: a tubular tensioning ring attached to the distal end of the tensioning wire and having a same external diameter as the elongated member; an imaging sensor having a rectangular cross section, arranged at a distal end of the head; and a tubular distal shell arranged longitudinally around the imaging sensor and having an inner diameter identical to or slightly larger than a diagonal of the rectangular cross section of the imaging sensor; wherein a tubular jacket sheathes the elongated member and the tensioning ring of the head.