A speculum for the insertion and expanding of a body cavity. The speculum comprises a plurality of blades pivotally connected around a ring-shaped frame, the first ends thereof extending longitudinally and meeting at a point distant from the frame to form a generally bulbous end and the second ends which are manipulated to rotate the blades about the frame. A rotating action of the second ends causes the first ends to angularly move away from each other to expand the bulbous end, and hence the body cavity. A series of block pivotally attached to the frame interact with the second ends to form a ratcheting locking means to lock the blades at certain positions between a closed position and an open position.