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Semispinalis Thoracis Muscle
Muscular System

Semispinalis Thoracis Muscle

Musculus semispinalis thoracis

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Quick Facts

Origin: Transverse processes of T6-T11 vertebrae.

Insertion: Spinous process of C6-T4 vertebrae.

Action: Extends and rotates the trunk.

Innervation: Medial branches of posterior rami of thoracic nerves.

Arterial Supply: Dorsal branches of posterior intercostal arteries.

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Origin

The semispinalis thoracis muscle originates from the transverse processes of the sixth to eleventh thoracic vertebrae. There can be variations between individuals regarding the origin sites for the semispinalis muscles (Tubbs, Shoja and Loukas, 2016).

Insertion

The fibers of the semispinalis thoracis muscle travel superiorly along the upper back regions and insert onto the spinous processes of the sixth cervical to fourth thoracic vertebrae. There can be variations between individuals regarding the insertion sites for the semispinalis muscles (Tubbs, Shoja and Loukas, 2016).

Key Features & Anatomical Relations

Overall, the semispinalis muscles are the more superficial of the three muscles of the transversospinal muscles. They are intrinsic muscles of the back and are found along the upper back and posterior neck regions. They are long, flat skeletal muscles that are composed of three parts:

- semispinalis capitis, which is the superior portion;

- semispinalis colli, which is the middle portion;

- semispinalis thoracis, which is the large, inferior portion.

The semispinalis muscles are located:

- superficial to the suboccipital and multifidus muscles;

- deep to the trapezius, splenius capitis, splenius colli, and erector spinae muscles;

- medial to the levatores costarum breves and longi muscles;

- lateral to the interspinales muscles.

Actions

The semispinalis thoracis muscle is involved in multiple actions:

- during unilateral contraction, it rotates the trunk to the opposite side;

- during bilateral contraction, it extends the trunk (Netter, 2011).

References

Netter, F. H. (2011) Atlas of Human Anatomy. Netter Basic Science Series: Saunders/Elsevier.

Tubbs, R. S., Shoja, M. M. and Loukas, M. (2016) Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. Wiley.

Learn more about this topic from other Elsevier products

Semispinalis Capitis

ScienceDirect image

The semispinalis capitis, which is the largest and most prominent of the posterior neck muscles, arises from the transverse process of the upper thoracic spines and is inserted into the occiput below the superior nuchal line.

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Complete Anatomy

The world's most advanced 3D anatomy platform

Complete Anatomy