Development of the optic nerve of the rat - Investigative ...

Volume 14
Number 10
Rat optic nerve 735
Fig. 4. Cross-section of the optic stalk of a 15.5-day-old fetus. Proliferating stalk cells form
a cluster in the upper center. Axons have invaded into the peripheral zone of the stalk. Epoxy
section, toluidine blue. *260.
Fig. 5. Longitudinal section of the optic stalk of a 15.5-day-old fetus. Axons extend mainly
into the lower periphery of the stalk ( *), A small number of axons are seen in the upper
periphery also (arrow). The cluster of the stalk cell extends about 0.5 mm. behind the globe.
Epoxy section, toluidine blue. *180.
Several elongating stalk cells maintain their
basal attachments and become the marginal
limit of the optic nerve. The original
basement membrane of these cells is prominent
beneath the cytoplasm. Axonal processes
are found in the newly formed lateral
intercellular spaces, first in the basal
portion in the fissure zone and eventually
all around the stalk (Fig. 5).
The continuity between the pigment
epithelium of the retina and the cells of
the optic stalk is broken on the fourteenth
day. The thick connective tissue separates
the pigment epithelium from the optic
stalk on the seventeenth day. The cluster
of the elongated stalk cells proliferate
rapidly at their apical portion and differentiate
into glia cells.
Axons. During the fourteenth to sixteenth
day, cells in the inner layers of the
retina and of the central nervous system
show profound proliferation and differentiation.
Also, the outer layer of the
optic cup differentiates into the pigment