An assembly for maintaining an extended access channel in tissue, the assembly comprising: a channel retractor, having: a lumen from an opening at a proximal end of the channel retractor to an opening at a distal end of the channel retractor, the lumen providing a first portion of an access channel; a longitudinal centerline of the lumen; a first gate track to receive a slide gate to press an extended retractor radially outward relative to the longitudinal centerline of the lumen; and a second gate track to receive a second slide gate to press a second extended retractor radially outward relative to the longitudinal centerline of the lumen; a first extended retractor with: a proximal portion that extends out of the proximal end of the channel retractor; a distal portion that extends out of the distal end of the channel retractor; and an intermediate portion between the proximal portion and the distal portion; and a first slide gate adapted to fit within the first gate track to retain the first extended retractor between the first slide gate and the channel retractor and thus maintain the first extended retractor away from the longitudinal centerline of the lumen, such that, when the first extended retractor has the distal portion extending beyond the distal end of the channel retractor for retaining tissue to provide the extended access channel, inserting the first slide gate into the first gate track causes the distal portion of the first extended retractor to remain separated from the longitudinal centerline of the lumen to maintain the extended access channel. a channel retractor, having: a lumen from an opening at a proximal end of the channel retractor to an opening at a distal end of the channel retractor, the lumen providing a first portion of an access channel; a longitudinal centerline of the lumen; a first gate track to receive a slide gate to press an extended retractor radially outward relative to the longitudinal centerline of the lumen; and a second gate track to receive a second slide gate to press a second extended retractor radially outward relative to the longitudinal centerline of the lumen; a lumen from an opening at a proximal end of the channel retractor to an opening at a distal end of the channel retractor, the lumen providing a first portion of an access channel; a longitudinal centerline of the lumen; a first gate track to receive a slide gate to press an extended retractor radially outward relative to the longitudinal centerline of the lumen; and a second gate track to receive a second slide gate to press a second extended retractor radially outward relative to the longitudinal centerline of the lumen; a first extended retractor with: a proximal portion that extends out of the proximal end of the channel retractor; a distal portion that extends out of the distal end of the channel retractor; and an intermediate portion between the proximal portion and the distal portion; and a proximal portion that extends out of the proximal end of the channel retractor; a distal portion that extends out of the distal end of the channel retractor; and an intermediate portion between the proximal portion and the distal portion; and a first slide gate adapted to fit within the first gate track to retain the first extended retractor between the first slide gate and the channel retractor and thus maintain the first extended retractor away from the longitudinal centerline of the lumen, such that, when the first extended retractor has the distal portion extending beyond the distal end of the channel retractor for retaining tissue to provide the extended access channel, inserting the first slide gate into the first gate track causes the distal portion of the first extended retractor to remain separated from the longitudinal centerline of the lumen to maintain the extended access channel.