Posterior branches of thoracic nerves

Posterior branches of thoracic nerves
Diagram of the distribution of the cutaneous branches of the posterior divisions of the spinal nerves.
Details
From	thoracic nerves
Latin	rami posteriores nervorum thoracicorum
*Anatomical terms of neuroanatomy* [edit on Wikidata]

The posterior branches of thoracic nerves branch from the dorsal rami of the thoracic nerves.

Branches

Medial branches

The medial branches of the posterior divisions of the upper six thoracic nerves run between the semispinalis dorsi and multifidus, which they supply. They then pierce the rhomboidei and trapezius, and reach the skin by the sides of the spinous processes.

The medial branches of the lower six are distributed chiefly to the multifidus and longissimus, occasionally they give off filaments to the skin near the middle line.

Lateral branches

The lateral branches increase in size from above downward.

They run through or beneath the Longissimus dorsi to the interval between it and the Iliocostales, and supply these muscles; the lower five or six also give off cutaneous branches which pierce the Serratus posterior inferior and Latissimus dorsi in a line with the angles of the ribs.

The lateral branches of a variable number of the upper thoracic nerves also give filaments to the skin.

The lateral branch of the twelfth thoracic, after sending a filament medialward along the iliac crest, passes downward to the skin of the buttock.

Medial cutaneous branches

The medial cutaneous branches of the posterior divisions of the thoracic nerves descend for some distance close to the spinous processes before reaching the skin, while the lateral branches travel downward for a considerable distance—it may be as much as the breadth of four ribs—before they become superficial; the branch from the twelfth thoracic, for instance, reaches the skin only a little way above the iliac crest.

Additional images

Areas of distribution of the cutaneous branches of the posterior divisions of the spinal nerves.
Diagram of the course and branches of a typical intercostal nerve.

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

Spinal nerves

Cervical	C1 C2 C3 C4 C5 C6 C7 C8 anterior Cervical plexus Brachial plexus posterior Posterior branches of cervical nerves Suboccipital – C1 Greater occipital – C2 Third occipital – C3

Thoracic	T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 anterior Intercostal Intercostobrachial – T2 Thoraco-abdominal nerves – T7–T11 Subcostal – T12 posterior Posterior branches of thoracic nerves

Lumbar	L1 L2 L3 L4 L5 anterior Lumbar plexus Lumbosacral trunk posterior Posterior branches of the lumbar nerves Superior cluneal L1–L3

Sacral	S1 S2 S3 S4 S5 anterior Sacral plexus posterior Posterior branches of sacral nerves Medial cluneal nerves

Coccygeal	anterior Coccygeal plexus posterior Posterior branch of coccygeal nerve

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