Disclosed is a seal membrane and assembly including the concave-channel. The seal membrane includes a proximal opening, a distal aperture, and a sealing wall from the distal aperture extending to the proximal opening. The sealing wall includes a proximal surface and a distal surface. The distal aperture is formed by a sealing lip for accommodating the inserted instrument and forming a gas-tight seal. The sealing wall includes a main rotary-wall and multiple concave-channels.