A tube or skeleton for a steerable catheter includes a cylindrical body structured to permit bending in at least one bending direction and to resist bending in directions transverse to the bending direction. The cylindrical body may include a laser cut metal tube, wires bent and connected to one another, or one or more coiled wires with axial support wires attached to the coil to define one or more bending directions to form bending segments. The skeleton includes axially stiff portions that resist compression when a pull wire is pulled to cause bending movement. The axially stiff portions may include a backbone, an alignment of pivot structures, connected axially extending portions of wire elements, or axially extending support wires or rods. Two or more bending portions may be provided, each with different bending directions. Complex bending shapes may be provided by arranging the segments in rotated positions along the skeleton.