Musculature: Topographical Anatomy

3 Musculature: Topographical Anatomy

3.1 The Back Muscles and Thoracolumbar Fascia


A The thoracolumbar fascia as a partition between the intrinsic and nonintrinsic back muscles

The trapezius muscle has been completely removed and the latissimus dorsi has been partially removed on the right side to reveal the thoracolumbar fascia. The superficial layer of the thoracolumbar fascia separates the intrinsic back muscles from the nonintrinsic muscles that have migrated to the back.

Note: The superficial layer of the thoracolumbar fascia is located close to the spinal column just beneath the skin, where it is heavily reinforced and serves as the origin for the extensive tendon of the latissimus dorsi. Lateral to the origin, the superficial layer is pushed beneath both the tendon and the muscle, thereby losing direct contact to the subcutaneous tissue. Along its entire width, medial to lateral, the superficial layer covers the intrinsic back muscles.

3.2 The Intrinsic Back Muscles: Lateral and Medial Tracts


A Course of the thoracolumbar fascia

Posterior view. To reveal the thoracolumbar fascia, both shoulder girdles and the extrinsic back muscles have been removed (except for the serratus posterior superior and inferior and the aponeurotic origin of the latissimus dorsi on the right side).


B Lateral tract of the intrinsic back muscles

Posterior view. Portions of the superficial layer of the thoracolumbar fascia have been removed on the left side of the back to expose the lateral tract muscles (iliocostalis, longissimus, and splenius muscles). The levatores costarum and intertransversarii muscles, also part of the lateral tract, are covered here by the iliocostalis and longissimus muscles (see C and D).

Note that the thoracolumbar fascia on the back of the neck is continuous with the deep layer of the nuchal fascia.


D Medial tract of the intrinsic back muscles (with the entire lateral tract removed)

Posterior view. The entire lateral tract (except for the intertransversarii and levatores costarum) has been removed, along with portions of the medial tract, to demonstrate the various individual muscles of the medial tract.

Note the origin of the transversus abdominis from the deep layer of the thoracolumbar fascia in the lumbar region (left side).

On the right side, the deep fascial layer and multifidus muscle have been removed to display the intertransversarii (lateral tract) and the quadratus lumborum (posterior [deep] abdominal muscle).

3.3 The Intrinsic Back Muscles: Short Nuchal Muscles


C Origin and insertion of the short nuchal muscles

Suboccipital region, posterior view. The colored areas indicate the origins (red) and insertions (blue) of the muscles.

3.4 The Thoracic Wall Muscles and Endothoracic Fascia

3.5 Thoracoabdominal Junction: The Diaphragm


A The diaphragm, superior view

The diaphragm consists of three parts: costal, lumbar, and sternal. As the muscle that separates the thoracic and abdominal cavities, the diaphragm has characteristic apertures for the passage of the esophagus, inferior vena cava, and aorta (see Cb and Db).


B The diaphragm, inferior view

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Jul 25, 2021 | Posted by in ANATOMY | Comments Off on Musculature: Topographical Anatomy

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