The Ligaments uniting the Lamina
The ligamenta flava are thick plates of closely woven yellow elastic tissue, interposed between the laminae of two adjacent vertebrae. The first connects the epistropheus with the third cervical, and the last the fifth lumbar with the sacrum. Each ligament extends from the medial and posterior edge of the intervertebral foramen on one side to a corresponding point on the other; above, it is attached close to the inner margin of the inferior articular process and to a well-marked ridge on the inner surface of the laminae as far as the root of the spine; below, it is fixed close to the inner margin of the superior articular process and to the dorsal aspect of the upper edge of the laminae.
Thus each ligamentum flavum, besides filling up the interlaminar space, enters into the formation of two articular capsules; they do so to a greater extent in the thoracic and lumbar regions than in the cervical, where the articular processes are placed wider apart. When seen from the front after removing the bodies of the vertebrae, they are concave from side to side, but convex from above downward; they make a more decided transverse curve than the arches between which they are placed. This concavity is more marked in the thoracic, and still more in the lumbar region than in the cervical; in the lumbar region the ligamenta flava extend a short distance between the roots of the spinous process, blending with the interspinous ligament, and making a median sulcus when seen from the front; there is, however, no separation between the two parts. In the cervical region, where the spines are bifid, there is a median fissure in the yellow tissue which is filled up by fibro-areolar tissue. The ligaments are thickest and strongest in the lumbar region; narrow but strong in the thoracic; thinner, broader, and more membranous in the cervical region.