The trocar housing is located in a trocar head (1) on a trocar channel (2) that has a closing valve, together with a seal (7) and valve flap (6) that is arranged in an closed position inclined in the trocar channel. The seal is inserted in the valve flap with its free end (6') being rounded off to the proximal side. There may be a narrow surrounding edge seal (13) on which the valve flap's seal may lie. A pipe section (11) may be inserted in the trocar head on which the valve flap lies, and where there may be a circumferential chamfer (12) with a constant angle between 10 - 30 deg . There may be direction specific guides (14) on the distal side of the valve flap in the trocar head.
