The lumbar fascia is an anatomic structure of the

lumbar region In tetrapod anatomy, lumbar is an adjective that means ''of or pertaining to the abdominal segment of the torso, between the diaphragm and the sacrum.'' The lumbar region is sometimes referred to as the lower spine, or as an area of the back i ...

. It consists of a band or sheet of

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

fibres, primarily

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...

, that attaches, stabilizes, encloses and separates muscles not limited to the lumbar region as the name suggests, but extending upwards over the

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

to the neck and downwards over the muscles covering the

sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part ...

. The upper

thoracic The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cr ...

portion is thin while the lumbar and sacral regions are thicker and stronger.

Function

The lumbar fascia binds the deep muscles of the back to the spine and to the transverse processes of the vertebrae. Additionally the lumbar fascia is an attachment for the

gluteus maximus muscle The gluteal muscles, often called glutes are a group of three muscles which make up the gluteal region commonly known as the buttocks: the gluteus maximus, gluteus medius and gluteus minimus. The three muscles originate from the ilium and sa ...

and the

latissimus dorsi muscle The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from L ...

Extent

The posterior layer covers the

loin The loins, or lumbus, are the sides between the lower ribs and pelvis, and the lower part of the back. The term is used to describe the anatomy of humans and quadrupeds, such as horses, pigs, or cattle. The anatomical reference also applies to ...

and continues upwards on the back of the thorax and the neck while middle and the anterior layers are confined to the lumbar region.

Attachments

Posterior layer

Medially, the posterior layer attaches to the tips of the lumbar and sacral spines and the

interspinous ligament The interspinous ligaments (interspinal ligaments) are thin and membranous ligaments, that connect adjoining spinous processes of the vertebra in the spine. They extend from the root to the apex of each spinous process. They meet the ligamenta f ...

s. To the sides it blends with the middle layer at the lateral border of the erector spinae muscle group that extends the vertebral column (bending the spine so the head moves back relative to the chest), also known as

sacrospinalis The erector spinae ( ) or spinal erectors is a set of muscles that straighten and rotate the back. The spinal erectors work together with the glutes (gluteus maximus, gluteus medius and gluteus minimus) to maintain stable posture standing or si ...

in older texts and more recently as extensor spinae,^{/sup> though this term is not in widespread use. Superiorly it continues on to the back of the thorax where it attaches to the vertebral spines and the ribs, inferiorly to the posterior quarter of the outer lip of the Iliac crest
The crest of the ilium (or iliac crest) is the superior border of the wing of ilium and the superiolateral margin of the greater pelvis.
Structure
The iliac crest stretches posteriorly from the anterior superior iliac spine (ASIS) to the posteri ...
.

Middle layer

Medially, the middle layer attaches to the tips of the lumbar transverse processes

The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...
and the transverse ligaments, laterally, it blends with the anterior layer at the lateral border of the quadratus lumborum, and superiorly it attaches to the lower border of the 12th rib and to the lumbocostal ligament and inferiorly, it attaches to the posterior part of the intermediate area of the Iliac crest.^{/sup>

Anterior layer

Medially, the anterior layer attaches to the vertical ridges on the anterior surface of the lumbar transverse processes, laterally it blends with the middle layer at the lateral border of the quadratus lumborum and superiorly, it forms the lateral arcuate ligament, extending from the tip of the first lumbar transverse process to the 12th rib and inferiorly, it attaches to the inner lip of the iliac crest
The crest of the ilium (or iliac crest) is the superior border of the wing of ilium and the superiolateral margin of the greater pelvis.
Structure
The iliac crest stretches posteriorly from the anterior superior iliac spine (ASIS) to the posteri ...
and iliolumbar ligament
The iliolumbar ligament is a strong ligament passing from the tip of the transverse process of the fifth lumbar vertebra to the posterior part of the inner lip of the iliac crest (upper margin of ilium).
Course
It forms the thickened lower bo ...
.

References

Vleeming, A., Pool-Goudzwaard, A., Stoeckart, R., van Wingerden, J., & Snijders, C. (1995). The Posterior Layer of the Thoracolumbar Fascia, Its Function in Load Transfer From Spine to Legs. Spine, 20(7), 753-758. https://dx.doi.org/10.1097/00007632-199504000-00001

Abdomen
Fascia

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