Superficial Layer of the Intrinsic Back Muscles

The Splenius Muscle Group

Human neck muscles, illustration
SEBASTIAN KAULITZKI/Getty

The superficial layer of the intrinsic back muscles contains the uppermost deep back muscles.

In contrast to extrinsic muscles, the intrinsic back muscles are deeply located; in other words, they are closer to the bones than to the skin. The intrinsic back muscles are subdivided into 3 layers: The superficial layer, the intermediate layer and the deep layer. This article talks about the superficial layer of the intrinsic back muscles.

Superficial Layer of the Intrinsic Back Muscles Overview

As the name suggests, the superficial layer of the intrinsic back muscles sits on top of the other 2 layers in this group. The superficial layer is comprised entirely of the splenius muscles – splenius cervicis and splenius capitis. Together the splenius muscles cover the vertically oriented paraspinals (which are deeper in and comprise the intermediate layer of the intrinsic back muscles.)

The word splenius refers to a bandage. (It is taken taken from the Latin word for bandage, which is “splenion”) And in a sense, bandaging is what the splenius muscles do to the paraspinals (the intermediate intrinsic layer) - as well as to those vertically oriented muscles that make up the deepest intrinsic layer. The splenius muscles (and therefore the superficial layer of the intrinsic back muscles) serve to hold these deeper layers in position.

Related:  The Paraspinal Muscles

The splenius captius and cervicalis cover the area from the bottom of the neck (C-7) down to the upper part of the thoracic spine (T-3 or T-4.) They start at the center of the spine at those levels, and together make a “V” shape - with the sides of the “V” very thick and the central indentation quite shallow.

The splenius capitis is positioned above the splenius cervicalis but, again, the two form one shape and act together.

The individual muscle fibers of the splenius capitis and cervicalis orient on a diagonal. Beginning at the midline of the spine, the fibers angle up to the skull and cervical vertebrae (C1-C3 or C4.)

Let's learn a bit more about the individual muscles of the superficial layer of the intrinsic back muscles.

Splenius Capitis

As mentioned above, the splenius capitis muscle starts at the midline of the spine, spanning the levels between your 7th cervical vertebra to your 3rd or 4th (it varies) thoracic vertebrae. More specifically, the splenius capitis arises from the nuchal ligament, which is a very strong ligament of the neck, itself arising from the ligament that connects the tips of your spinous processes all the way down the spine. (This is called the supraspinous ligament.) The spelnius capitus also arises from the spinous processes of C7-T3 or T4.

Related: Intro to Spinal Ligaments

The splenius capitis muscle then angles up and out to attach onto your skull at 2 places: The mastoid process, which is located behind and towards the very bottom of the ear, and at the nuchal line of the skull, which is at the back of your skull but at a level higher than the mastoid process.

Splenius Cervicalis

Like the splenius capitis, the splenius cervicalis starts at the midline of the spine, spanning the levels between your 7th cervical vertebra to your 3rd or 4th (it varies) thoracic vertebrae. More specifically, the splenius cervicalis arises from the nuchal ligament, which is a very strong ligament of the neck, itself arising from the ligament that connects the tips of your spinous processes all the way down the spine. (This is called the supraspinous ligament.) The spelnius cervicalis also arises from the spinous processes of C7-T3 or T4.

Related: Images: Parts of a Vertebra (Where Spinal Muscles Attach)

Unlike the splenius capitis, the splenius cervicalis attaches onto the transverse processes of the first 3 or 4 upper cervical (neck) bones, in other words at C1 – C3 or C4.

When both sides of the splenius machine act together, the result is neck extension, which equates to bringing the head back toward the back of the neck. When only one side is contracting, the splenius muscles help tilt and/or rotate the neck to the side of the contraction.

Sources

Moore, K., Dalley, A. Clinically Oriented Anatomy. Fifth. Edition. Lippincott, Williams & Wilkins. 2006. Baltimore. Philadelphia, PA

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