Answer:
between 20,000 and 25,000
The outer periphery of the inter-vertebral disk is composed of strong fibrous tissue called the Annulus fibrosus. This is a tough circular exterior of the inter-vertebral disc that surrounds the soft inner core, the nucleus pulposus. The outer portion is composed of a ring of ligament fibers that encases the inner core of the disc and securely connects the spinal vertebrae above and below the disc.
The difference between plant cells and animal cells is that most animal cells are round whereas most plant cells are rectangular. Plant cells have a rigid cell wall that surrounds the cell membrane. Animal cells do not have a cell wall.
