An organ assist system having a closed fluid system having a ring-shaped prosthetic contactively surrounding at least a portion of a body part, including bladders adapted for selectable dilation and contraction in response to varying fluid pressure therewithin, a fluid pump, and apparatus for pressurizing the bladders; and a control unit for controlling operation of at least the fluid pump; pressure sensors within the fluid system; a power source, and shut off valves. The pressurization apparatus includes pressure cells arranged in an array, each pressure cell having a shut-off valve at its inlet, and a shut-off valve at its outlet, the shut-off valves being controlled by the control unit such that the pressurization apparatus is operable to provide a range of pressurizations to the bladders of the prosthetic for applying a controlled variable pressurizing effect to the body part thereby.