When divided horizontally, it exhibits, to some extent, the appearance of a biconvex lens, while a
coronal section of its central part presents a somewhat triangular outline. It is shorter than the caudate nucleus and does not extend as far forward.
Relations It is deep/medial to the
insular cortex, with which it is coextensive; the two are separated by intervening structures. It is lateral to the caudate nucleus and
thalamus, and is seen only in sections of the hemisphere. It is bounded laterally by a lamina of a white substance called the
external capsule, and lateral to this is a thin layer of gray substance termed the
claustrum. Its anterior end is continuous with the lower part of the head of the caudate nucleus and with the
anterior perforated substance. Inferiorly, there is a groove upon the surface of the lenticular nucleus that accommodates the
anterior commissure.
Components In a coronal section through the middle of the lentiform nucleus, two medullary laminae are seen dividing it into three parts. The lateral and largest part is of a reddish color, and is known as the
putamen, while the medial and intermediate are of a yellowish tint, and together constitute the
globus pallidus; all three are marked by fine radiating white fibers, which are most distinct in the putamen. ==Pathology==