Abstract: A tissue retractor has a retractor body delimiting a central device opening and proximal and distal body ends. The proximal body end has a proximal flange having inner and outer proximal flange edges and a proximal flange body extending, with the retractor not delivered, away from the central device opening. The distal body end has a distal flange having inner and outer distal flange edges and a distal flange body extending, with the retractor not delivered, away from the central device opening. The retractor body has a retractor neck having a proximal end connected to the inner proximal flange edge and a distal end connected to the inner distal flange edge. The proximal flange has a proximal flange portion having concavity facing the distal flange, which has a distal concave flange portion having concavity, where the concavities are facing the same direction, and is dome segment-shaped or spherical crown-shaped.