1. A surgical access system for accessing a surgical target site in a patient, said system comprising: a retractor assembly having: a retractor body including a first arm having a distal end with a first blade connector and a first longitudinal axis extending through the distal end, a second arm having a distal end with a second blade connector and a second longitudinal axis extending through the second distal end, and a third arm having a distal end with a third blade connector and a third longitudinal axis extending through the distal end, wherein the third arm is situated between the first arm and the second arm; a first retractor blade releasably coupled to the first blade connector of the first arm, a second retractor blade releasably coupled to the second blade connector of the second arm, and a third retractor blade releasably coupled to the third blade connector of the third arm, the first, second, and third retractor blades capable of simultaneous advancement over a tissue dilator to the surgical target site while in a closed position and thereafter selectively opened to create an operative corridor to the surgical target site, wherein when positioned at the surgical target site the first retractor blade is a caudal-most retractor blade, the second retractor blade is a cephalad-most retractor blade, and the third retractor blade is a posterior retractor blade; wherein the retractor body is operable to: move the first retractor blade away from the second and third retractor blades in a first caudal direction; move the second retractor blade away from the first and third retractor blades in a second cephalad direction; linearly translate the third retractor blade relative to the first and second retractor blades in a third direction in a line transverse to the first and second directions; rotate the first retractor blade about the first longitudinal axis to move a distal end of the first retractor blade relative to a proximal end of the first retractor blade; and rotate the second retractor blade about the second longitudinal axis to move a distal end of the second retractor blade relative to a proximal end of the second retractor blade; and a supplemental retractor blade assembly attachable to each of the first retractor blade and second retractor blade, the supplemental retractor blade assembly including an elongated supplemental retractor blade and a crosslink, the crosslink slidably engageable with a first holding element that extends distally relative to the retractor body from the first retractor blade and a second holding element that extends distally relative to the retractor body from the second retractor blade, and the supplemental retractor blade including a blade surface, a handle, and an engagement region between the blade surface and handle that engages with the crosslink.