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# Serratus posterior

The serratus posterior muscles are two thin muscles over the upper and lower back [ribs](https://durgical.com/en/anatomy/ribs/); they help move the ribs when breathing.

Official name: Serratus posterior superior muscle

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## What it is

Two thin muscles over the upper and lower back ribs.

## What it does

Helps move the ribs when breathing.

## Key points

- Two thin sheets of the intermediate layer of the back, between the scapular muscles and the erector spinae
- Serratus posterior superior lies under the rhomboids; serratus posterior inferior lies under latissimus dorsi

## Key facts

**Origin**
Superior: [nuchal ligament](https://durgical.com/en/anatomy/nuchal-ligament/), spinous processes of C7–T3; inferior: spinous processes of T11–L2

**Insertion**
Superior: upper borders of ribs 2–5; inferior: lower borders of ribs 9–12

**Action**
Superior: elevates ribs; inferior: depresses ribs (respiratory role weak; mainly proprioceptive in some texts)

**Nerve**
Superior: [intercostal nerves](https://durgical.com/en/anatomy/intercostal-nerves/) T2–T5; inferior: ventral rami T9–T12

**Blood supply**
[Posterior intercostal arteries](https://durgical.com/en/anatomy/posterior-intercostal-arteries/); subcostal and [lumbar arteries](https://durgical.com/en/anatomy/lumbar-arteries/) (inferior)

## Relations

**Superficial**
Superior: [rhomboids](https://durgical.com/en/anatomy/rhomboid-major-muscle/) and [trapezius](https://durgical.com/en/anatomy/trapezius-muscle/); inferior: [latissimus dorsi](https://durgical.com/en/anatomy/latissimus-dorsi-muscle/)

**Deep**
Superior: [splenius](https://durgical.com/en/anatomy/splenius-capitis-muscle/) and the erector spinae; inferior: the erector spinae and the [thoracolumbar fascia](https://durgical.com/en/anatomy/thoracolumbar-fascia/)

## How to find it

Not felt separately. In a dissection they appear as thin sheets once the rhomboids or latissimus dorsi are turned back, the superior with fibres running down and outward, the inferior with fibres running up and outward.

## On imaging

Not seen separately on routine imaging: they are thin sheets under the rhomboids and latissimus dorsi. On axial CT or MRI they may be traced as a thin layer over the erector spinae reaching the upper and lower ribs. In upper back pain, imaging looks at the [spine](https://durgical.com/en/anatomy/region/spine/), the ribs and the costovertebral joints rather than at these muscles.

## Clinical notes

- Serratus posterior superior is described in some texts as a source of deep aching pain under the upper medial border of the [scapula](https://durgical.com/en/anatomy/scapula/)

## Anatomical variants

- Origin, insertion, size and nerve supply vary; either muscle may be thin or have fewer slips

## Test yourself

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

## Where do the serratus posterior superior and inferior insert?

Superior: upper borders of ribs 2–5; inferior: lower borders of ribs 9–12.

## What are the actions of the serratus posterior superior and inferior?

Superior elevates the ribs, inferior depresses them; the respiratory role is weak.

## Which muscles cover the serratus posterior superior and inferior?

The rhomboids cover the superior; latissimus dorsi covers the inferior.

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

## Its names

**Official Latin (TA2)**
musculus serratus posterior superior; musculus serratus posterior inferior TA2 2236

**Official Spanish (DeCS)**
Músculos serratos posteriores

**English (TA2)**
Serratus posterior superior muscle

**Also called**
musculus serratus dorsalis cranialis

## Related

- [Intercostal nerves](https://durgical.com/en/anatomy/intercostal-nerves/)
- [T12 vertebra](https://durgical.com/en/anatomy/t12/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Back, Extrinsic Muscles](https://www.ncbi.nlm.nih.gov/books/NBK537216/).

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Representative model, for educational purposes only.

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