Nucleus pulposus is the jelly-like substance in the middle of the spinal disc. It is the remnant of the notochord

Notochord

The notochord is a flexible, rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes...

 . It functions to distribute hydraulic pressure in all directions within each disc

Annulus fibrosus disci intervertebralis

Each intervertebral fibrocartilage is composed, at its circumference, of laminæ of fibrous tissue and fibrocartilage, forming the annulus fibrosus.-Spelling notes:...

 under compressive loads. The nucleus pulposus consists of chondrocyte-like cells, collagen

Collagen

Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

 fibrils, and proteoglycan

Proteoglycan

Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan chain. The point of attachment is a Ser residue to which the glycosaminoglycan is joined through a tetrasaccharide bridge...

 aggrecan

Aggrecan

Aggrecan also known as cartilage-specific proteoglycan core protein or chondroitin sulfate proteoglycan 1 is a protein that in humans is encoded by the ACAN gene. This gene is a member of the aggrecan/versican proteoglycan family...

s that have hyaluronic long chain

Hyaluronan

Hyaluronan is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues...

s which attract water. Attached to each hyaluronic chain are side chains of chondroitin sulfate

Chondroitin sulfate

Chondroitin sulfate is a sulfated glycosaminoglycan composed of a chain of alternating sugars . It is usually found attached to proteins as part of a proteoglycan. A chondroitin chain can have over 100 individual sugars, each of which can be sulfated in variable positions and quantities...

 and keratan sulfate

Keratan sulfate

Keratan sulfate , also called keratosulfate, is any of several sulfated glycosaminoglycans that have been found especially in the cornea, cartilage, and bone. It is also synthesized in the central nervous system where it participates both in development and in the glial scar formation following an...

.

External links

• Image at spinesource.com
• Presentation on synthetic nucleus pulposus