Intervertebral disc T3–T4

Discus intervertebralis

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What it is
Fibrocartilage cushion between the T3 and T4 vertebral bodies: a tough ring (annulus fibrosus) around a gel core (nucleus pulposus).
Function
Absorbs shock and lets adjacent vertebrae rock and twist on each other.
Size
≈ 31 × 24 mm, 5 mm thick here (discs make up ~25% of spinal length)
Clinical note
Discs lose water with age, which is why people get slightly shorter; a torn annulus lets the nucleus herniate onto a nerve root.