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# T3–T4 nucleus

The nucleus pulposus is the soft, gel-like centre of the [T3-T4](https://durgical.com/en/anatomy/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 points

- A central herniation here meets a cord with little blood supply to spare, at the top of the mid-thoracic watershed

## 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](https://durgical.com/en/anatomy/posterior-longitudinal-ligament/), then a narrow canal holding the [spinal cord](https://durgical.com/en/anatomy/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.

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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

- [T3–T4 disc](https://durgical.com/en/anatomy/t3-t4/)
- [T3 vertebra](https://durgical.com/en/anatomy/t3/)
- [T4 vertebra](https://durgical.com/en/anatomy/t4/)

Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=56248&filter=ths_termall&q=N%C3%BAcleo%20Pulposo); [Anatomy, Back, Nucleus Pulposus](https://www.ncbi.nlm.nih.gov/books/NBK535373/); [Anatomy, Back, Intervertebral Discs](https://www.ncbi.nlm.nih.gov/books/NBK470583/); [7.3 The Vertebral Column](https://openstax.org/books/anatomy-and-physiology-2e/pages/7-3-the-vertebral-column) (OpenStax (Rice University), 2022) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/t3-t4-spine-and-pelvis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/t3-t4-spine-and-pelvis/