a division of the gray matter of the spinal cord into nine laminae (I-IX) and a gray area around the central canal (area X) based on cytoarchitectural features; the posterior (dorsal) horn is composed of laminae I-VI, the intermediate zone of lamina VII, and the anterior (ventral) horn of laminae VIII and IX; general correlation of laminae with some of the major nuclei: I, posteromarginal nucleus; II, substantia gelatinosa; III and IV, nucleus proprius cornu dorsalis; V and VI, sometimes described as containing the spinal reticular formation; VII, Clarke nucleus, intermediomedial, and intermediolateral cell columns; VIII, commissural nuclei, interneurons; and IX, motor nuclei of the anterior horn.