A system including an overtube configured to radially expand facilitates insertion of instruments in a patient. The system is directed to an overtube comprising an elongated body having a distal end and a proximal end, the overtube configured to radially expand from an insertion configuration to an expanded configuration, and including at least one articulation section having at least one degree of freedom and including a main channel expandable in the radial direction, and at least one additional channel. The at least one articulation section can radially expand. The system may include a radially expandable overtube having an optical channel configured to receive an optical device. The main channel and/or the at least one additional channel may be sized to receive one or more medical instruments.