According to the invention, the endoprosthesis comprises an expandable support structure or stent (2) held between the inner tissue structure (4) and the outer covering (10), wherein the outer covering (10) Is composed of a blood-compatible flexible synthetic material which penetrates into the inner structure (4) through an opening provided in the support structure (2).本発明によれば、体内人工組織は、内側組織構造体(4)と外側被覆(10)との間に保持される拡張可能な支持構造体又はステント(2)を備え、外側被覆(10)が、支持構造体(2)に設けられた開口を通じて内側構造体(4)に侵入する血液適合性の柔軟な合成材料で構成される。