Which muscle originates from the sacrum and iliac crest via the thoracolumbar fascia?

• A. Spinalis cervicis
• B. Latissimus dorsi
• C. Longissimus thoracis
• D. Quadratus lumborum

Answer: (C)

The statement describes a muscle with a broad origin from the sacrum and iliac crest through the thoracolumbar fascia. That pattern is characteristic of the latissimus dorsi. The thoracolumbar fascia provides a strong, continuous origin across the lower back and pelvis, tying the sacrum and iliac crest into a single sheet from which the latissimus dorsi can arise. This large back muscle then runs up to insert on the humerus, enabling actions like shoulder extension, adduction, and medial rotation.

The other muscles listed don’t match this origin pattern. Spinalis cervicis is a neck-focused muscle that originates along the spine higher up. Longissimus thoracis mainly arises from lumbar transverse processes and thoracic region attachments, with its origin not classically described as from the sacrum and iliac crest via the thoracolumbar fascia. Quadratus lumborum does attach near the iliac crest and interacts with the thoracolumbar fascia, but it doesn’t originate from the sacrum and iliac crest via that fascia in the same broad, fascia-contained way as latissimus dorsi.