Horizontal and amacrine cells allow for communication laterally between the neurons. The photoreceptors synapse on bipolar cells, and the bipolar cells synapse on the ganglion cells. In addition to the photoreceptors, there are four other cell types in the retina. There are 5 primary types of cells in the retina ‘Eye Anatomy’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License. Details about the functions of each region are in the text. The fovea (dark red section) is a small portion of the retina where visual acuity is highest, and the optic disc is located where the optic nerve (tan region) leaves the eye. The retina (red line) is located along the back of the eye. The visible regions of the eye include the cornea, pupil (gray region), and iris (blue region). This region is called the optic disc and is the location of the blind spot in our visual field. Where the optic nerve leaves, there are no photoreceptors since the axons from the neurons are coming together. The optic nerve projects to the brain from the back of the eye, carrying information from the retinal cells. In the middle of the bowl is the fovea, the region of highest visual acuity, meaning the area that can form the sharpest images. The retina covers the entire back portion of the eye, so it’s shaped like a bowl. The retina is the light-sensitive region in the back of the eye where the photoreceptors, the specialized cells that respond to light, are located. Proper focusing requires the lens to stretch or relax, a process called accommodation. The lens refracts light to focus images on the retina. The lens is located behind the pupil and iris. The iris is the colored portion of the eye that surrounds the pupil and along with local muscles can control the size of the pupil to allow for an appropriate amount of light to enter the eye. The pupil is the opening in the iris that allows light to enter the eye. It covers the pupil and the iris and is the first location of light refraction. The cornea is the transparent, external part of the eye. The front of the eye consists of the cornea, pupil, iris, and lens.
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