What is the structure of the lens cortex and nucleus?
In the center (#3 in photomicrograph) tightly packed cells have lost their nuclei and become packed by special transparent proteins (crystallins) to form so-called lens fibers. New lens cells are added to the margin of the lens throughout life from the lens epithelium, but the cells at the cortex and nucleus (center) of the lens do not undergo turnover or replacement and are therefore the oldest cells in the body of an adult. The lens is avascular and nourished by diffusion from the aqueous and vitreous. The radius of curvature of the anterior surface averages 10 mm, but it is subject to marked changes during accommodation. Because the lens nucleus is formed by increasing density of cortical cells, cortex and nucleus are considered together. Both are made up exclusively of cells derived from the lens epithelium. The common designation of “lens fiber” for the cortical cells is a misnomer for the elongated cells of the lens substance. Lens cortical cells are elongated and on cross-sectio
