68: Phylogeny and development of organ of vision Flashcards
(33 cards)
What is the first step in eye development?
The development starts with the optic vesicles forming from the diencephalon, a part of the brain.
What is Lens Placode Formation?
The optic vesicles signal the nearby surface ectoderm to thicken, forming the lens placode.
What happens during Lens Pit Formation?
The lens placode invaginates to create the lens pit.
What occurs during the transition from Optic Vesicle to Optic Cup?
Simultaneously, the optic vesicle invaginates to form a bilayer optic cup.
What is Optic Stalk Formation?
The optic stalk develops to connect the optic vesicle with the forebrain.
What is Lens Vesicle Creation?
The lens pit further develops into the lens vesicle.
What is Cornea Induction?
The lens vesicle induces the formation of the cornea.
What happens during Retinal Development?
The optic cup forms the retina; the outer layer becomes the retinal pigment epithelium and the inner layer differentiates into other retinal layers.
What occurs during Iris and Ciliary Body Formation?
The anterior rim of the optic cup, along with neural crest cells, forms the iris and the ciliary body.
What causes Myopia (Nearsightedness) and how is it corrected?
Distant objects appear blurry because the image is focused in front of the retina. Corrected using concave lenses, which spread the light before it reaches the eye.
What causes Hyperopia (Farsightedness) and how is it corrected?
Close objects appear blurry as images are focused behind the retina. Convex lenses are used to correct this by converging the light before it hits the eye.
What is Astigmatism and how is it corrected?
Causes blurry vision at certain distances due to an irregularly shaped cornea or lens, corrected with specially shaped lenses.
What is Presbyopia and how is it corrected?
Age-related condition where the eye loses the ability to focus on near objects, often corrected with reading glasses.
What are the Outer Eye Layers and their functions?
o Sclera: Tough, fibrous tissue providing structural support and protection.
o Cornea: Transparent, dome-shaped structure that refracts light towards the pupil, crucial for focusing light onto the retina.
What are the Middle Eye Layers and their functions?
o Choroid Layer: Vascular layer supplying nutrients to the retina, contains pigmented cells to prevent light scattering.
o Iris and Pupil: Iris regulates the amount of light entering the eye by controlling pupil size.
o Lens: Behind the iris, adjusts focus through accommodation.
o Aqueous Humor: Watery fluid maintaining intraocular pressure and nourishing the cornea and lens.
What are the Inner Eye Layers and their functions?
o Retina: Contains photoreceptor cells (rods and cones) for detecting light and color, crucial for sending visual information to the brain.
o Vitreous Humor: Gel-like substance supporting the eye’s shape and aiding in light transmission to the retina.
What is Convergent Evolution?
This is the phenomenon where two unrelated lineages evolve similar traits independently, often as a response to analogous environmental pressures.
What was the initial feature of the Eye Shape and Lens in early evolution?
Initially featured an elliptical shape with a spherical, non-adjustable lens.
How do teleosts and some sharks and rays achieve focusing?
Teleosts (bony fish) use a musculus retractor to pull the lens towards the retina for focusing, whereas sharks and rays use a musculus protractor to move the lens away.
What is the Tapetum Lucidum and its function in some species?
Some species may have this reflective layer, enhancing low-light vision.
How do amphibians achieve Lens Accommodation?
Achieved by moving the lens forward to focus on nearby objects.
What kind of vision do amphibians have?
Equipped with rods and cones for color vision.
What features do amphibians have for eye protection?
Features a fixed upper eyelid and a transparent nictitating membrane (membrana nicticans) for protection.
How do pupil shapes differ in diurnal and nocturnal reptile species?
Diurnal species typically have round pupils; nocturnal species have vertical pupils.
