T3–T4 nucleus !
The nucleus pulposus is the soft, gel-like centre of the T3-T4 disc in the mid-back; it works like a water cushion that spreads the load.
Official name: T3-T4
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What it is
The soft, gel-like centre (nucleus pulposus) of the T3–T4 disc.
What it does
Works like a water cushion: it turns pressure from above into outward push on the fibre ring, spreading the load. It is under the most pressure when you bend forward and lift.
Key facts
- Where
- Centre of the T3–T4 disc, slightly toward the back, inside the annulus fibrosus
- Function
- Notochord-derived gel (about 70–90% water, proteoglycans); turns axial load into annulus tension; small in thin thoracic discs, herniation rare
Relations
- Behind
- Back of the annulus fibrosus and the posterior longitudinal ligament, then a narrow canal holding the spinal cord
Examination
- Normal arm reflexes with brisk knee and ankle jerks, ankle clonus or a Babinski sign place the lesion below the cervical cord and above the lumbar enlargement
On imaging
Sagittal T2 MRI compares its brightness with the discs above and below; a dark disc alone is common and often silent.
Common problems
- Squeezes out through a tear in the ring (herniation), usually backward and to one side, toward a nerve root.
- Loses water with age, so the disc gets thinner and stiffer.
How it is diagnosed
On MRI a healthy nucleus is bright on T2 images; a worn one turns dark ('black disc').
Treatment
- In a microdiscectomy only the loose piece that has pushed out is removed; most of the disc stays.
Clinical notes
- Compression here spares the arms: stiffness, weakness and numbness begin in the legs, and bladder symptoms tend to come later
- Leg upper motor neuron signs with a normal arm exam call for thoracic MRI; scanning only the neck can miss an upper thoracic disc
Test yourself
Think of the answer, then tap the question to see it.
Why is a central herniation of the T3–T4 nucleus a concern for the spinal cord?
The cord here has little blood supply to spare, at the top of the mid-thoracic watershed, and the canal is narrow.
How is the T3–T4 nucleus judged on sagittal T2 MRI?
By comparing its brightness with the discs above and below; a dark disc alone is common and often silent.
Where in the disc does the T3–T4 nucleus pulposus sit?
In the centre of the T3–T4 disc, slightly toward the back, inside the annulus fibrosus.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- nucleus pulposus T3-T4 TA2 1686
- Official Spanish (DeCS)
- Núcleo pulposo T3-T4 DeCS D000070614
- English (TA2)
- T3-T4
Related
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Back, Nucleus Pulposus; Anatomy, Back, Intervertebral Discs; 7.3 The Vertebral Column (OpenStax (Rice University), 2022) · adapted, CC BY 4.0.
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Representative model, for educational purposes only.
