lens sits in the optic cup the
vitreous body develops in the space between the lens and the inner wall of
the optic cup. The early lens vesicle is hollow. Later, cells of its posterior
pole begin to elongate to form
primary lens fibers that run antero-posteriorly obliterating the cavity. The
cells of the anterior pole remain cuboidal and become the
anterior epithelium. The
hyaloid artery passes through the vitreous space to vascularize the
posterior aspect of the developing lens. Later, the part supplying the lens
disappears; its proximal part remains as the central artery of the
The lens transforms the overlying surface ectoderm into the anterior epithelium
cornea and its primary stroma (acellular). Neural crest/mesenchymal cells,
surrounding the optic cup, migrate to form the posterior corneal endothelium and
invade the primary stroma forming the secondary stroma (cellular).
Optic Cup: - Retina, Ciliary body, Iris - Retina: The cells of the
inner wall of the optic cup divide to form the multilayered, sensory
neural retina; the outer wall of the cup forms the
pigment layer of the retina. The neural retina comes to consist of a
3-neuron chain:1) rods and cones, 2) bipolar cells, and 3) ganglion cells.
Growth of the axons of the ganglion cells into the optic stalk forms the optic
nerve. The edge of the optic cup transforms into the non-light sensitive
portions of the retina, on the posterior aspect of the iris and ciliary bodies.
Ciliary body - Its outer epithelial layer is pigmented, a forward extension of
the pigment layer of the optic cup; its inner epithelial layer is a
non-pigmented extension of the neural retina. The stroma of the ciliary body,
including its muscle cells, arises from mesenchyme. Iris - The inner and outer
epithelial layers of the iris are pigmented. The stroma of the iris arises from
mesenchyme; in the stroma are the sphincter and dilator muscles (which arise
from its pigmented epithelial cell layer).