A. Embryonic Nucleus. The primary fiber cells in humans are quite similar to bovine primary fibers in both size and arrangement. Location = center of the equatorial plane.
B-F. Fetal nucleus. In the fetal nucleus (B-E), considerable reduction in cross- sectional size is evident as regions further from the lens center are examined. The rounded profiles (B-C) gradually become flattened and irregular (D-F), but do not have the hexagonal shape seen in bovine lenses. Short rows of cells (C) become organized into radial cell columns (E), however, these are more difficult to discern in the human than in the bovine. The fibers continue to flatten (F) and the profiles take on an undulating appearance which is also seen in panels G and H.
B. Location = 0.6 mm from the lens center.
C. Location = 1 mm from the lens center.
D. Location = 1.3 mm from the lens center.
E. Location = 1.5 mm from the lens center.
F. Location = 2 mm from the lens center.
G. Juvenile Nucleus. Two distinct cell sizes are characteristic of the juvenile nuclear region, where larger cells are interspersed among the highly flattened cell profiles. Location = 2.4 mm from the lens center.
H. Adult Nucleus. Cells of the adult nuclear region are highly compressed, making their profiles difficult to distinguish. Location = 3.5 mm from the lens center.