sensory

Anatomy of the Eye: Structures and Functions

• Lamellated (Pacinian) corpuscles are large oval structures located deep in the reticular dermis and hypodermis, and are responsible for sensing coarse touch, pressure, and high-frequency vibrations.
• The eye is composed of three concentric tunics or layers: fibrous layer, vascular layer (uvea), and retina.
• The fibrous layer consists of the sclera, which is the tough external layer, and the cornea, which is the transparent avascular anterior part.
• The vascular layer, or uvea, includes the choroid, ciliary body, and iris. The choroid is a well-vascularized layer that prevents light from entering the eye, while the ciliary body consists of smooth muscle fibers that affect the shape of the lens. The iris, which covers part of the lens, determines the color of the eye.
• The retina is composed of two layers: the pigmented layer, which absorbs scattered light and forms part of the protective blood-retina barrier, and the neural layer, which contains various neurons and photoreceptors.
• The neural layer of the retina consists of nine distinct layers, including the rod and cone layer, outer limiting layer, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglionic layer, nerve fiber layer, and inner limiting membrane.
• The rod cells in the retina are extremely sensitive to light and allow for vision in low light conditions, while the cone cells produce color vision in bright light.
• Specialized areas of the retina include the optic disc (blind spot), fovea centralis (area of maximal visual acuity), and macula lutea (area with carotenoids that protect cone cells).
• The lens is a transparent, avascular, biconvex structure located behind the iris, and it focuses light onto the retina. It is held in place by the ciliary zonule and can change shape for visual accommodation.
• The vitreous body is a gel-like connective tissue that occupies the large vitreous chamber behind the lens, providing support to the eye.
• Accessory structures of the eye include the conjunctiva, which is a thin mucosa that covers the sclera and inner surface of the eyelids, the eyelids, which are pliable and protective structures consisting of skin, muscle, tarsus, and sebaceous glands, and the lacrimal glands, which produce tears for lubrication.
• The eye is a complex organ with various structures and functions that allow for vision and perception of the surrounding environment.