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  1. The photoreceptor layer consisting of the rods and cones is the outer
    layer of the retina.

  2. The outer limiting membrane is formed by the junctional complexes
    between Müller’s cells and the membranes of photoreceptor cells.

  3. The outer nuclear layer contains the nuclei of rod and cone cells and
    the surrounding cytoplasm (perikarya).

  4. The outer plexiform layer contains rod and cone synapses as well as the
    cell processes of bipolar, horizontal, and photoreceptor cells.

  5. The inner nuclear (bipolar) layer is composed of the nuclei and
    perikarya of the bipolar and amacrine cells as well as the nuclei of
    Müller’s cells.

  6. The inner plexiform layer consists of amacrine cells dispersed between
    the processes of bipolar and ganglion cells. This layer is responsible for
    modulation of signals from the ganglion to the photoreceptor cells.

  7. The ganglion cell layer contains the ganglion cells separated by the
    cytoplasm of astrocyte-like glia (Müller’s cells).

  8. The nerve fiber layer consists of axons of the ganglion cells that will
    form the optic nerve.

  9. The internal limiting membrane is located between the vitreous body
    and the retina. The photoreceptors are of two types: rods and cones.
    The nuclei of the rods and cones are found in the outer nuclear layer
    and extend across the outer limiting membrane in one direction and
    toward the outer plexiform layer in the other direction. The outer seg-
    ment is the photon-sensitive portion of the rod and cone and contains
    membranous disks. Rhodopsin is composed of opsin and retinal. It is
    responsible for transduction of light (photons) into hyperpolarization
    of the cell membrane. Rhodopsin is present in the disks of the outer
    segment of the rod. The inner segment contains numerous mitochon-
    dria, glycogen, and protein synthetic apparatus. Rods are responsible
    for night vision, whereas the cones are responsible for color vision,
    which is best resolved at the fovea. The fovea, which is the center of
    the macula, is composed exclusively of cones and is the site of optimal
    resolution.


The choroid is a highly vascular layer that consists of three parts:
stroma, choriocapillaris, and Bruch’s membrane. Blood supply to the retina
is derived from the choriocapillaris of the choroid. The sclera is a layer of
relatively avascular dense connective tissue.


404 Anatomy, Histology, and Cell Biology

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