Endoscope for the minimally invasive examination or surgical treatment of a patient, comprising - a flexible tubular shaft for insertion into the patient, with a distal end , and - a grip for holding the endoscope , a distal end of the grip being attached to a proximal end of the shaft , - wherein the endoscope is provided with at least one working channel for internally guiding a surgical instrument and/or carrying water or air to or providing suction at the distal end of the shaft , - at least one groove extending substantially axially along the outer face of the shaft from the vicinity of the proximal end to the distal end , where the groove ends in a recess in the distal end , and - the at least one working channel is provided by at least one hollow tube that is removably housed in the groove , and - wherein a convex hull (CH) or a completion (C) of the shaft to a simple geometric shape without the hollow tube is the same as a convex hull (CH) or completion (C) of the shaft with the hollow tube , characterized in that for better adaptation to length changes of the groove as a result of bending the shaft the tube has at least one free section in which the groove and the tube are dimensioned relative to one another in such a way that the tube has play in the axial direction, but also in respect of a rotation of the tube around its local longitudinal axis, by way of the tube having, in the straight extended state of the shaft , an exterior cross-section which is slightly smaller than an interior cross-section of the groove , and in that beyond and/or between the free section or free sections respectively are sections of the tube which are inserted more firmly into the groove , in that they are either pressed in exploiting the elasticity of the tube, or, alternatively or additionally, glued in with a not very strong adhesive. - a flexible tubular shaft for insertion into the patient, with a distal end , and - a grip for holding the endoscope , a distal end of the grip being attached to a proximal end of the shaft , - wherein the endoscope is provided with at least one working channel for internally guiding a surgical instrument and/or carrying water or air to or providing suction at the distal end of the shaft , - at least one groove extending substantially axially along the outer face of the shaft from the vicinity of the proximal end to the distal end , where the groove ends in a recess in the distal end , and - the at least one working channel is provided by at least one hollow tube that is removably housed in the groove , and - wherein a convex hull (CH) or a completion (C) of the shaft to a simple geometric shape without the hollow tube is the same as a convex hull (CH) or completion (C) of the shaft with the hollow tube , in that for better adaptation to length changes of the groove as a result of bending the shaft the tube has at least one free section in which the groove and the tube are dimensioned relative to one another in such a way that the tube has play in the axial direction, but also in respect of a rotation of the tube around its local longitudinal axis, by way of the tube having, in the straight extended state of the shaft , an exterior cross-section which is slightly smaller than an interior cross-section of the groove , and in that beyond and/or between the free section or free sections respectively are sections of the tube which are inserted more firmly into the groove , in that they are either pressed in exploiting the elasticity of the tube, or, alternatively or additionally, glued in with a not very strong adhesive. <EOS>