Eye Development Quiz

Eye Development

• The eye develops from three embryonic layers: neuroectoderm, surface ectoderm, and mesoderm.
• On day 22, optic vesicles appear on the forebrain, later forming the optic cup and lens vesicle.
• The optic vesicle contacts the surface ectoderm, inducing the formation of the lens placode.
• The lens placode invaginates and detaches from the surface ectoderm, forming the lens vesicle.
• The optic vesicle invaginates to form the double-layered optic cup.
• The choroid fissure allows the hyaloid artery to reach the inner chamber of the eye.
• The choroid fissure closes in week 7, forming the future pupil.
• The optic stalk connects the optic vesicle to the prosencephalon and becomes the optic nerve.

Derivatives of the Optic Cup

• The retina is formed by two layers: outer pigmented epithelium and inner photoreceptive layer.
• The ciliary body is covered by epithelial layers from the optic cup and connective tissue from mesenchyme.
• The iris is covered by epithelial layers from the optic cup and contains neuroectodermal smooth muscle fibers.
• The optic nerve derives from the optic stalk and contains the central retinal artery and vein.

Other Eye Structures

• The choroid and sclera are formed from mesenchyme surrounding the optic cup.
• The cornea is transparent and avascular, while the sclera is opaque and vascular.
• The anterior chamber forms in mesenchyme between the lens vesicle and surface ectoderm.
• The iridopupillary membrane disappears, allowing communication between the anterior and posterior chambers.
• The cornea develops from surface ectoderm and mesenchyme.

Congenital Defects

• Coloboma iridis occurs when the choroid fissure fails to close.
• Persistent iridopupillary membrane is caused by incomplete resorption of the iridopupillary membrane.
• Congenital cataracts are caused by a lens becoming opaque during intrauterine development, sometimes due to rubella infection.

Eye Histology

• The cornea is the outermost connective tissue layer containing pain receptors and responsible for light transmission.
• The sclera covers the posterior 5/6ths of the eye and contains collagen and elastic fibers.
• The lens is a biconvex structure suspended by zonular fibers and responsible for focusing light.
• The uvea is the vascular middle layer of the eye.
• The choroid contains a network of capillaries.
• The ciliary body contains the ciliary muscle responsible for lens accommodation.
• The iris regulates light entering the eye by adjusting the pupil size.
• The sphincter pupillae constricts the pupil (miosis), while the dilator pupillae dilates it (mydriasis).
• The retina is a thin tissue lining the posterior wall of the eye, composed of seven cell types.

Retina Cell Types

• The retinal pigment epithelium (RPE) absorbs excess light, stores vitamin A, supports photoreceptors, and phagocytizes shed photoreceptor segments.
• Photoreceptors (rods and cones) are light-sensitive neurons responsible for vision.
• Rods are sensitive to low light and responsible for night vision.
• Cones provide color vision and high acuity.
• Bipolar cells connect photoreceptors to ganglion cells.
• Horizontal and Amacrine cells modify visual data to enhance borders and contrast.
• Muller cells provide metabolic support to retinal cells, similar to oligodendrocytes.

Test your knowledge on the fascinating process of eye development. This quiz covers the embryonic layers involved, the formation of the optic vesicle, and the derivatives of the optic cup. Challenge yourself and learn more about how the eye structure evolves from an early stage.