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Psoas Fascia
Connective Tissue

Psoas Fascia

Fascia psoae

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The psoas fascia is a thick layer of epimysial fascia that covers the anterior surface of psoas major muscle. The epimysium is a well-defined layer of dense irregular connective tissue, which completely envelopes the muscle belly. It consists primarily of type I collagen fibers, which are tightly arranged to form a relatively strong fibrous covering of the muscle (Standring, 2016). Blood vessels travel through this collagenous sheath around the whole skeletal muscle, providing the skeletal muscle with blood supply. Nerves travel through the epimysium around the muscle, thus, innervating it.

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Related parts of the anatomy

Anatomical Relations

Proximally, the psoas fascia blends with the medial arcuate ligament and blends inferiorly with the iliac fascia as the iliopsoas fascia. Medially, it has the same attachment points as the underlying muscle, the transverse processes and bodies of the lumbar vertebrae, the tendinous arches superiorly, and to the pelvic brim inferiorly. Laterally, the iliopsoas fascia merges with the anterior lamina of the thoracolumbar fascia, which covers the quadratus lumborum muscle.


Psoas fascia covers and protects the underlying iliac muscle. The Femoral sheath is formed by an inferior prolongation of the iliopsoas and transversalis fascia superiorly.

List of Clinical Correlates

—Psoas abscess


Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.

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The fascia is also defined as a “the fascial system consists of the three-dimensional continuum of soft, collagen containing, loose and dense fibrous connective tissues that permeate the body” by Fascia Nomenclature Committee (Bordoni and Whitte, 2018), an as “masses of connective tissue large enough to be visible to the unaided eye” by Gray’s Anatomy (Standring, 2016).

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