Bones such as the vertebrae, or bones of the spine, have an outer and inner layer. Cortical bone is a term used to describe the hard compact bone on the outside, while trabecular bone refers to the porous spongy bone inside. Both are affected by osteoporosis, but it is the trabecular bone that is most vulnerable. There is constant activity inside the bone. When we take a closer look, we see that bone is made up of living cells, called osteocytes, that are surrounded by a hard mineral material.
Blood vessels bring nourishment and minerals to the bone.
Throughout our lives, scavenger cells called osteoclasts come along and eat away old bone. The eaten away areas are then repaired by osteoblasts, tiny construction worker cells, whose job it is to build the new bone. Calcium and other minerals finish the job by hardening the area. This on going process of breakdown and replacement is known as bone remodeling. From infancy to early adulthood, more bone is built than removed.