An implantable access device including a port for receiving and guiding a filament, such as a needle, into an entry region of the device. The port includes a plate for receiving a filament, and at least two walls extending upwardly from the plate. The walls are shaped and positioned to guide the filament moving between opposing first and second ends of the plate through an entry region defined between the walls at the second end of the plate. Preferably, a greatest distance between the walls is at least five times greater than a height of the walls, so that the port provides a large filament strike area, yet has a small overall height. In addition, a greatest distance between the ends of the plate is also preferably at least five times greater than the height of the walls, to further increase the filament strike area without increasing height.