A Bioroid is an android built partially or totally with biological components. Differentiated from a cyberized human by the lack of Cyberbrain.
It is never explained whether biologic components are 'replaceable' in the same way as mechanical ones, but despite sustaining fatal injuries during the climax of 2nd Gig, Proto is seen again in the Ghost in the Shell: S.A.C. Solid State Society movie.
Bioroids are a main theme of Appleseed, another of Shirow Masamune's creations.