8.2 – Internal Anatomy of the Eye ANATOMY & PHYSIOLOGY The Eyeball Hollow sphere Wall is composed of three layers ◦ Fibrous layer ◦ Vascular layer ◦ Sensory layer Interior filled with fluid called humors ◦ Help maintain shape ◦ Two types: aqueous and vitreous (more on these in a second) Lens of the eye divides it into two chambers ◦ Anterior (aqueous) segment ◦ Posterior (vitreous) segment General Structures of the Eye The Fibrous layer Two main parts ◦ Sclera ◦ White connective tissue layer ◦ Seen anteriorly as the “white” of the eye ◦ Cornea ◦ Transparent central anterior portion of sclera ◦ Allows for light to pass through ◦ One of four refractory media of the eye ◦ “Window on the world” ◦ Most exposed part of the eye ◦ Vulnerable to damage but easily repairable ◦ Only tissue that is able to be transplanted without rejection Vascular layer: The Choroid Most posterior section of the vascular layer Blood rich, nutritive layer of the eye Heavily pigmented ◦ Prevents light from scattering inside the eye Moving anterior, becomes modified to form two smooth muscle structures ◦ Ciliary body ◦ Iris Vascular Layer: The Ciliary Body Contains muscles that controls the shape of the lens Intrinsic smooth muscles Attached to the lens by a suspensory ligament called the ciliary zonule Vascular Layer: Iris Pigmented with rounded opening (pupil) Serves as “diaphragm” of the eye ◦ Allows light to pass through Intrinsic smooth muscles ◦ Circularly and radially arranged ◦ Close vision and bright light, circular muscles contract and pupil constricts ◦ Distant vision and dim light, radial fibers contract and pupil dilates Sensory Layer Composed of delicate, two-layered retina ◦ Pigmented layer ◦ Outer layer ◦ Absorb light and prevent light from scattering ◦ Neural layer ◦ Inner layer ◦ Contains the receptor cells ◦ Rods and cones Sensory Layer (cont.) The rods and cones are distributed over most of the retina ◦ No photoreceptors are distributed where the optic nerve leave the eyeball ◦ Known as the optic disk ◦ Lateral to the blind spot is the fovea centralis ◦ Tiny pits that contain only cones ◦ Area of greatest visual acuity Chambers of the Eye Central to the eye at the anterior end is the lens ◦ Helps focus light on the retina ◦ We will focus on this more on Monday The lens divides the eye into two chambers ◦ Anterior segment - aqueous chamber ◦ Posterior segment – vitreous chamber Anterior (Aqueous) Chamber Located anterior to the lens Contains a clear watery fluid called aqueous humor ◦ Serves as the third refractory media of the eye ◦ Provides nutrients to the lens and cornea ◦ Helps maintain intraocular pressure ◦ Reabsorbed by the Canal of Schlemm Posterior (Vitreous) Chamber Located posterior to the lens Contains a gel-like substance called the vitreous humor ◦ Helps reinforce the eyeball by maintaining intraocular pressure ◦ Last of the refractory media of the eye For Next Time: Reading: ◦ pg. 288-291 Homework: ◦ 8.2 Worksheet (the first #5).