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. The osteon is the structural unit of compact bone. Haversian system is a microscopic, structural unit of compact bone also called the osteon.The osteons are arranged in multiple layers or rings called concentric lamella.nswered by The Community. Making the world better, one answer at a time. The osteon is the structural unit of compact bone. Haversian system is a microscopic, structural unit of compact bone also called the osteon.