{"id":3066,"date":"2020-12-13T21:28:09","date_gmt":"2020-12-13T19:28:09","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/neurohistology\/eyes-eyelids\/internal-layer\/"},"modified":"2021-12-04T10:47:44","modified_gmt":"2021-12-04T08:47:44","slug":"internal-layer","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/nervous-system\/eyes-eyelids\/internal-layer\/","title":{"rendered":"Internal layer"},"content":{"rendered":"\n

The internal layer of the eye is made of the retina. The retina is a nerve tissue consisting of photoreceptor cells that transform absorbed light into electrical nerve impulses.<\/div><\/p>\n\n\n\n
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Figure 1. Layers of the retina<\/strong><\/figcaption><\/figure><\/div>\n\n\n\n

Retina<\/h3>\n<\/span>\n\n\n

The retina is the sensory part of the eye. It is the deepest layer of the eye. <\/p>\n\n\n\n

It can be divided into two divisions:<\/p>\n\n\n\n

  1. Retinal pigment epithelium<\/li>
  2. Neural retina<\/li><\/ol>\n\n\n<\/span>\n

    Retinal pigment epithelium<\/h4>\n<\/span>\n\n\n

    The outer layer, which is attached to the choroid — the choriocapillary layer, through Bruch’s membrane. The cells are connected via a gap and tight junctions.<\/p>\n\n\n\n

    The functions of the retinal pigment epithelium are quite diverse:<\/p>\n\n\n\n

    1. Form the blood-retinal barrier<\/strong> via the tight junctions<\/li>
    2. Help the visual function of the photoreceptors<\/li>
    3. Maintains the photoreceptors by phagocytosis of waste<\/li>
    4. Absorbs the light passing through the retina and prevents reflection<\/li><\/ol>\n\n\n\n
      \n
      <\/span>\n

      Neural retina<\/h4>\n<\/span>\n\n\n

      The inner layer, containing two regions with distinct functions according to their name, a photosensitive region<\/strong> posterior to the ora serrata, and a non-photosensitive region<\/strong> anterior to it.<\/p>\n\n\n\n

      Together with the retinal pigment epithelium, the photosensitive region of the retina consists of 10 layers (from in-out, see Figure 2):<\/p>\n\n\n\n

      1. Internal limiting membrane<\/li>
      2. Nerve fiber layer<\/li>
      3. Ganglionic layer<\/li>
      4. Inner plexiform layer<\/li>
      5. Inner nuclear layer<\/li>
      6. Outer plexiform layer<\/li>
      7. Outer nuclear layer<\/li>
      8. External limiting membrane<\/li>
      9. Photoreceptors<\/li>
      10. Retinal pigmented epithelium<\/li><\/ol>\n<\/div>\n\n\n\n
        \n
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        Figure 2. Histological slide of the retina. The choroid is not a part of the retina<\/strong><\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n
        \n
        <\/span>\n

        Cells of the retina<\/h4>\n<\/span>\n\n\n

        The neural retina contains many types of cells, including photoreceptors, neurons, ganglion, and neuroglial cells.<\/p>\n\n\n\n

        There are two types of photoreceptor cells – rods<\/strong> (responsible for black-white\/dark-light vision), and cones<\/strong> (responsible for color vision), and over 30 types of renal ganglion cells, several types of neurons and neuroglial are present within the retina.<\/p>\n\n\n\n

        The distribution of the cones is concentrated at the fovea, while the rods are much more numerous and are located at the periphery.<\/p>\n\n\n\n