Pulposus

Pulposus refers to the nucleus pulposus, the gelatinous inner core of an intervertebral disc. Each disc sits between adjacent vertebral bodies and is composed of an outer fibrous ring called the annulus fibrosus surrounding the central nucleus pulposus, which acts as a cushion and shock absorber within the spine.

The nucleus pulposus originates embryologically from the notochord and, in the mature disc, consists largely of water, proteoglycans, and collagen type II. Its high water content gives it a gel-like consistency that allows the disc to distribute axial loads and adapt during movement. With aging, proteoglycan content declines and water content decreases, leading to disc dehydration and reduced height.

Functionally, the nucleus pulposus distributes pressure across the disc when the spine is loaded and works in concert with the annulus fibrosus to enable flexibility and load transfer. Its hydraulic properties help to absorb shocks during activities such as walking, lifting, and bending.

Clinical significance includes degeneration and herniation of the disc. Degenerative changes can reduce water content and weaken the annulus fibrosus, allowing nucleus material to protrude or extrude, potentially compressing adjacent nerves and causing pain, numbness, or weakness. Imaging typically shows higher water content in a healthy nucleus pulposus on T2-weighted MRI, with signal loss indicating dehydration or degeneration.