First of all, an optical drive can be a CD, DVD, or BluRay drive. The button isn't invisible, it's just hidden in plain site by design. The previous pictures show its location, but here is one more. This is a picture of the top of a 660 showing 2 drives.
What is difference between an osteon and osteocyte? An osteon is the functional unit of cortical bone. Osteons contain osteocytes, which are cells that produce bone matrix.
Answered by The Community. Making the world better, one answer at a time. osteons are the structural units of compact bone and therefore located in compact bone. essentially an osteon is hollow tube consisting of ring like structures called lamellae similar to rings of a tree. within the lamellae are lacunae.