The Eye
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| What are the three structural layers of the eye? | Corneoscleral coat, vascular coat and retina
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| Corneoscleral coat consist of what? | Sclera and cornea
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| The vascular coat consist of what? | The uvea (choroid and the stroma of the ciliary body and iris)
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| The retina consist of what? | Outer pigment epithelium, inner neural layer and the epithelium of the ciliary body and the iris
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| The anterior chamber is the space between what? | Cornea and the iris
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| The posterior chamber is the space between what? | Posterior surface of the iris and the anterior surface of the lens.
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| The vitreous chamber is the space between what? | The posterior surface of the lens and the neural retina.
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| As the neural tube closes the optic grooves form outpocketings called what? | Optic vesicles
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| As the optic vesicle grows laterally the forebrain becomes constricted forming what? | Optic stalk
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| The overlying ectoderm of the optic vesicle forms what? | Lens placode
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| The lens placode and the optic vesicle invaginates forming what? | Double layered optic cup
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| The inner layer of the optic cup becomes what? | Neural retina
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| The outer layer of the optic cup becomes what? | Retinal pigment epithelium
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| Grooves containing blood vessels develop along the inferior surface. They are called what? | Choroid fissures (enable the hyaloid vessels to reach the inner chamber of the eye)
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| The distal portions of the hyloid vessels degenerate but the proximal portions remain as what? | Central artery and vein of the retina
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| During the third month of gestation, the groth of the optic cup gives rise to what? | The ciliary body and iris
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| The key regulator gene for the eye is what? | PAX6
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| PAX6 initiates the formation of what? | A ridge of neural plate that forms a single eye field.
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| The signal for separation of the eye field is what? | Sonic hedgehog (SHH)
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| What structures of the eye are derived from ectoderm? | Lens, epithelium of the cornea, conjuctiva, lacrimal gland and its drainage system
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| What stuctures of the eye are derived from neural ectoderm? | Vitreous body, epithelium of the retina, iris, ciliary body, sphincter pupillae, dilator pupillae and the optic nerve
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| A cleft in the iris that may be associated with other congenital defects is called what? | Coloboma
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| When the lens becomes clouded during intrauterine life it is termed what? | Congenital cataracts (may be cause by maternal rubella infection)
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| When the eye is to small it is termed what? | Microphthalmia (caused by infections such as cytomegalovirus and toxoplasmosis)
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| Absence of an eye an eye is termed what? | Anophthalmia (accompanied by severe cranial abnormalities)
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| Absence of the lens is termed what? | Congenital aphakia (caused by mutations in PAX6 gene)
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| Fusion of the eyes is called what? | Cyclopia or synophthalmia (associated with holoprosencephaly)
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| Ansence of the iris is called what? | Aniridia (caused by mutations in the PAX6 gene)
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| WAGR is an acronym for what 4 diseases? | Wilm's tumor (cancer of the kidney), aniridia, genitourinary abnormalities and mental retardation
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| What are the five layers of the cornea? | Corneal epithelium, Bowman's membrane, corneal stroma, Descemet's membrane and corneal endothelium.
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| The corneal epithelium has what diagnostic features? | Nonkeratinized stratified squamous epithelium and it is connected to Bowman's membrane by HEMIDESMOSOMES
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| Bowman's membrane ends abruptly where? | Corneoscleral limbus (acts as a barrier to the spread of infection)
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| Corneal stroma (substantia propria) has what diagnostic feature? | Has layers of parallel bundles of collagen fibrils (normally avascular)
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| Descemet's membrane has what diagnotic feature? | It is an unusually thick basement membrane
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| Corneal endothelium does what for the eye? | Provides metabolic exchange between the cornea and the aqueous humor
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| The corneoscleral limbus is a transition zone between what? | Cornea and sclera
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| The limbus region, the iridocorneal angle, contains what? | The apparatus for the outflow of aqueous humor
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| Endothelium lined channels what merge to form the scleral venous sinus (canal of Schlemm)? | Trabecular network
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| The canal of Schlemm encircles the eyes and performs what function? | Drains aqueous humor from the anterior chamber of the eye
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| The vascular coat of the eye is known as what? | Uvea
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| The most anterior part of the vascular coat is what? | Iris (forms diaphragm of the lens)
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| The central apeture of the eye is known as what? | Pupil
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| The ciliary processes are covered by a double layer of columnar epithelium called what? | Ciliary epithelium
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| What are the three functions of the ciliary epithelium? | SECRETION OF AQUEOUS HUMOR, participation in the blood-aqueous barrier, secretion and anchoring of the zonular fibers that form the suspensory ligaments of the lens
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| Nonpigmented cells have the characteristics of what? | Fluid transporting epithelium (well developed zonula occludens)
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| Cells of the nonpigmented layer has a less developed junctional zone because they are held together by what? | Desmosomes and gap junctions (creates discontinuous spaces called ciliary channels)
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| An obstruction in the drainage of aqueous humor which leads to an increased intraocular pressure is called what? | Glaucoma (can damage the retina and cause blindness if not treated)
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| What are the 2 types of glaucoma? | Open-angle and closed angle glaucoma
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| Open-angle glaucoma is caused by what? | When the trabecular meshwork drains aqueous humor but the canal of Schlemm is blocked (most common type)
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| Closed-angle glaucoma is caused by what? | Results when the aqueous humor is unable to reach the trabecular meashwork because of inflammatory process of the uvea.
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| Surgery that uses a laser to burn holes in the trabecular meshwork (used to treat glaucoma) is called what? | Trabeculoplasty
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| Glaucoma can be treated with eye drops that contain what? | Carbonic anhydrase inhibitor (blocks carbonic anhydrase isoenzyme CA-II which plays impotant role in production of aqueous humor)
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| Photorecepters of the retina are what? | Rods and cones
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| Conducting neurons of the retina are what? | Bipolar and ganglion cells
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| Supporting cells of the retina are what? | Muller cells, microglial cells and astrocytes
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| What are the 10 layers of the retina? | Retinal pigment epithelium, rods and cones, outer limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion cell layer, optic nerve fibers, inner limiting membrane
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| A single layer of cuboidal cells connected by junctional complexes which helps form the blood-retina barrier is called what? | The retinal pigment epithelium
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| The blood-retina barrier does what function? | Isolates retinal cells from blood-bourne substances (cells rest on Bruch's membrane of the choroid layer)
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| The retinal pigment performs what function? | Absorption of light passing through the retina to prevent reflection and glare
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| A small shallow depression at the posterior pole of the optical axis of the eye is called what? | Fovea (fovea centralis) composed entirely of cones
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| The area surrounding the fovea is called what? | Macula lutea (yellow due to the presence of xanthophyll)
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| The site where the optic nerve exits the retina is called what? | Optic disc or papilla (potoreceptors are absent, blind spot of the eye)
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| if the potential space between the optic cup expands what can occur? | The neural retina pulls away from the retinal pigment epithelium (retinal detachment)
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| The most common cause of blindness in older individuals is what? | Age related macular degeneration (ARMD)
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| What are the 2 forms of macular degeneration? | Dry (atrophic, nonexudative) and wet (exudative, neovascular)
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| Dry ARMD is caused by what? | Degenerative lesions of the macula lutea (causes blind spots in the visual field)
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| Wet ARMD is caused by what? | Complications of dry ARMD where new blood vessels form (neovascular) in the area of the thickened Bruch's membrane
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| What are 2 diagnostic features of the lens? | Avascular and biconvex
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| The lens capsule is composed primarily of what? | Type IV collagen and proteoglycans (elastic)
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| In the lens, cuboidal cells are connected to subscapular epithelium via what? | GAP JUNCTIONS
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| The lens capsule is what? | Thick basal lamina produced by the anterior lens cells
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| The subcapsular epithelium is what? | Cuboidal cells only present on the anterior surface of the lens
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| Lens fibers are derived from what? | Subcapsular epithelial cells
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| Lens fibers lose their nuclei and other organelles when they become filled with proteins called what? | Crystallins
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| A disease that causes opacity of the lens is called what? | Cataracts (cause by a change in the solubility of lens proteins)
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| In cataract patients, when glucose levels are high what byproduct is produced that leads to this condition? | Sorbitol (decreases the solubility of crystallins)
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| Hyalocytes of the vitreous humor is responsible for what? | Synthesis of collagen fibers and glycosaminoglycans
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Created by:
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