A releasable mechanism such as a cap is adapted for use with an access sheath having an elongate tube and a handle structure disposed at a proximal end of the tube. The releasable mechanism is sized and configured to fit the handle structure, which is shaped like the bell of a horn, to further facilitate use with surgical instrumentation. The releasable mechanism may operate as a separate cap that snaps onto the handle structure to provide access pathways to the sheath. The releasable mechanism may also be disposed at a proximal end of a surgical instrument to be introduced into the access sheath such that it may be interlocked with the sheath. In a method of manufacturing a kink-resistant sheath, a wire is initially coated with a plastic material, the coated wire is then wrapped around a mandrel forming a plurality of windings, and the wound coated wire is heated until the plastic material melts and bonds the windings to form a wire-reinforced sheath. The plastic material is preferably polyurethane but may be a thermoplastic, a thermoset or any plastic material having hard and/or soft durometer. The wound coated wire may be heated by capturing the windings within a shrink tube or compressing the windings in a mold and heating the windings until the sheath is formed. In another aspect of the invention, a mandrel is used as part of an extrusion process. In another aspect of the invention, another coating or outside layer could be formed over the spring reinforcement by dipping in a solvent based solution. In yet another embodiment of the invention, a braid such as a polyester braid may be used instead of or in addition to the coil spring to form a kink-resistant sheath.