Final answer:
The inner part of intervertebral discs is called the nucleus pulposus, which is a gel-like substance with a high water content essential for cushioning and support. As age increases, the water content decreases, impacting disc thickness and flexibility. The anulus fibrosus is the outer layer that encases the nucleus pulposus.
Step-by-step explanation:
The inner part of the intervertebral discs is known as the nucleus pulposus. It is composed of a softer, more gel-like material, which provides the discs with their cushioning properties. This gel-like center has a high water content that helps it resist compression during weight-bearing activities. As we age, the water content in the nucleus pulposus decreases, leading to thinner discs and a reduction in flexibility and range of motion. Such changes can affect overall body height and increase the difficulty of bending movements.
In addition to the nucleus pulposus, the intervertebral discs also have an outer layer called the anulus fibrosus. This tough, fibrous layer encircles the nucleus pulposus and secures the discs to the adjacent vertebral bodies, effectively uniting them and providing padding during weight-bearing activities.