Trunk (thorax, abdomen, back)

Nucleus pulposus (Intervertebral disc core)

Nucleus pulposus disci intervertebralis

Origin

Central gel-like core rich in proteoglycans (aggrecan), type II collagen, and water (notochord remnant)

Insertion

Centrally enclosed by anulus fibrosus and cartilaginous endplates

Function

Acts as a hydraulic ball bearing and shock absorber, converting vertical axial load into radial hoop stress on the anulus

Innervation

Avascular and aneural in healthy state; nerve ingrowth occurs in disc degeneration

Movement & chain

Deforms and migrates dynamically opposite to spinal bending (migrates posteriorly during spinal flexion)

Palpation

Not palpated directly

Clinical

Herniated nucleus pulposus (HNP) causing radiculopathy/sciatica via mechanical pressure and inflammatory cytokines; degenerative disc disease (DDD).

Segmental innervation

C2–S1

In clinical practice

McKenzie directional preference exercises for disc centralization and ergonomic lifting instruction

Region in the model

Trunk (thorax, abdomen, back)