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# Sternothyroid

The sternothyroid is a strap muscle at the front of the neck, from the breastbone to the thyroid cartilage; it pulls the larynx down and lies over the thyroid.

Official name: Sternothyroid muscle

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## What it is

A strap muscle under the sternohyoid, to the thyroid cartilage.

## What it does

Pulls the larynx down; it lies right over the thyroid gland.

## Key points

- Lies directly on the thyroid gland, deep to the sternohyoid
- Its attachment to the oblique line of the [thyroid cartilage](https://durgical.com/en/anatomy/thyroid-cartilage/) blocks upward growth of the thyroid lobes, so a large goitre tends to extend down behind the [sternum](https://durgical.com/en/anatomy/sternum/) (retrosternal goitre)
- Near its upper end lie the [superior thyroid artery](https://durgical.com/en/anatomy/superior-thyroid-artery/) and the external branch of the [superior laryngeal nerve](https://durgical.com/en/anatomy/superior-laryngeal-nerve/), at the upper pole of the thyroid gland

## Key facts

**Origin**
Posterior manubrium; first [costal cartilage](https://durgical.com/en/anatomy/costal-cartilage/)

**Insertion**
Oblique line of the thyroid cartilage

**Action**
Depresses the larynx

**Nerve**
[Ansa cervicalis](https://durgical.com/en/anatomy/ansa-cervicalis/) (C2–C3)

**Blood supply**
Superior thyroid artery

## Relations

**Superficial**
[Sternohyoid](https://durgical.com/en/anatomy/sternohyoid-muscle/), with the superior belly of the [omohyoid](https://durgical.com/en/anatomy/omohyoid-muscle/) at its side

**Deep**
[Thyroid gland](https://durgical.com/en/anatomy/thyroid-gland/), [trachea](https://durgical.com/en/anatomy/trachea/) and larynx; lower down, behind the [manubrium](https://durgical.com/en/anatomy/manubrium-of-sternum/), the left [brachiocephalic vein](https://durgical.com/en/anatomy/brachiocephalic-vein/)

**Lateral**
[Carotid sheath](https://durgical.com/en/anatomy/carotid-sheath/) with the [common carotid artery](https://durgical.com/en/anatomy/common-carotid-artery/)

**Above**
Continued by the [thyrohyoid](https://durgical.com/en/anatomy/thyrohyoid-muscle/) from the oblique line up to the [hyoid bone](https://durgical.com/en/anatomy/hyoid-bone/)

## How to find it

Found in thyroidectomy by retracting the sternohyoid: it lies flat on the thyroid lobe and is lifted off the gland's capsule.

## On imaging

Ultrasound shows it as a thin dark band lying directly on the front of the thyroid lobe, deep to the sternohyoid. For a large goitre, a [chest](https://durgical.com/en/anatomy/region/chest/) radiograph may show a widened upper mediastinum with the trachea pushed aside; CT of neck and chest then shows how far the gland passes behind the sternum and how much it narrows the trachea, ideally without iodinated contrast if radioiodine is planned.

## Clinical notes

- Divided in its upper part when a large upper pole must be exposed, which spares its ansa cervicalis supply entering from below
- Strap muscle stuck to the thyroid gland may mean local invasion by cancer, and the involved muscle is then removed with the gland
- A retrosternal goitre can compress the trachea and the great veins at the thoracic inlet

## Development

Develops with the other strap muscles from the premuscle mass shared with the [tongue](https://durgical.com/en/anatomy/tongue/), which receives upper cervical nerves early; this is the basis of its ansa cervicalis supply.

## Related conditions

- [Goitre](https://durgical.com/en/conditions/goitre/)

## Test yourself

Think of the answer, then tap the question to see it.

## Why does a large goitre tend to extend down behind the sternum rather than up the neck?

The sternothyroid attaches to the oblique line of the thyroid cartilage and blocks upward growth of the thyroid lobes.

## Which structures lie near the upper end of the sternothyroid at the upper pole of the thyroid?

The superior thyroid artery and the external branch of the superior laryngeal nerve.

## What can strap muscle stuck to the thyroid gland mean at thyroidectomy?

Local invasion by cancer; the involved sternothyroid is then removed with the gland.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
musculus sternothyreoideus TA2 2173

**Official Spanish (DeCS)**
Músculo esternotiroideo

**English (TA2)**
Sternothyroid muscle

## Related

- [Ansa cervicalis](https://durgical.com/en/anatomy/ansa-cervicalis/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Head and Neck, Thyroid Muscles](https://www.ncbi.nlm.nih.gov/books/NBK541063/); [Anatomy, Head and Neck: Anterior Cervical Region](https://www.ncbi.nlm.nih.gov/books/NBK557475/); Anatomy of the Human Body (20th ed.): Development of the Muscles (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain.

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/sternothyroid-muscle/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/sternothyroid-muscle/