This shows what normal discs
look like in the lower back.
The central part has a significant amount of
water within it and behaves something like jello or like an expensive gel-filled
seat cushion.
This inner part of the disc, the nucleus, is a bright gray
on these pictures.
The outer part of the disc, the annulus, is a tough, fibrous
layer that is strong. It keeps the softer nucleus in place. It is dark on
these pictures and looks the same as the edges of the bone.
The inner part
of the bone, the bone marrow, contains cells that produce red and white blood
cells.
