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Eye
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Layers Cornealscleral layer (tunica fibrosa) Uvea (tunica vasculosa)
Retinal layer (tunica interna or nervosa)
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Supporting coat Vascular coat Retinal coat Ciliary body Cornea Sclera
Neural retina Iris Non-nervous anterior portion Ciliary processes Sheaths of nerve Retinal pigment epithelium Choroid Supporting coat Vascular coat Retinal coat
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Refractive media Cornea Lens Suspensory ligament (Zonule)
Aqueous humor Vitreous body
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Chambers/body Anterior chamber Posterior chamber Vitreous chamber
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Accessory structures Eyelid Lacrimal apparatus Extrinsic eye muscles
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Schlemm’s canal Cornea Limbus Anterior chamber Lens Ciliary muscle Zonule Ora serrata Iris Posterior chamber Ciliary body and process Vitreous body Choroid Photosensitive retina Sclera Optic papilla Fovea Sclera Choroid Pigment epithelium 1 2 3 4 Optic nerve
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Cornealscleral layer Cornea (anterior 1/6 of eye) Epithelium
Bowman’s membrane Substantia propria Descemet’s membrane Endothelium
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Corneal epithelium Bowman’s membrane Substantia propria Descemet’s membrane Corneal endothelium
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Cornealscleral layer Sclera (posterior 5/6 of eye)
Dense fibrous connective tissue with elastic and collagenous fibers Tendons of extrinisic eye muscles insert into this layer Optic nerve region: sieve-like Forms lamina cribrosa
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Cornea Scleral sulcus Posterior chamber Anterior chamber Lens Sclera Vitreous body Lamina cribrosa
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Limbus Corneo-scleral junction
Corneal epithelium continuous with bulbar conjunctiva Blood vessels that supply cornea Endothelium Spaces of Fontana: the trabecular meshwork Canal of Schlemm: circumferential vessel that drains aqueous humor into episcleral veins (in limbus)
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Cornea Limbal conjunctiva Limbal stroma Anterior chamber Trabecular meshwork Canal of Schlemm Iris Posterior chamber
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Uvea Middle, highly vascular layer Three components: Choroid
Ciliary body Ciliary processes Ciliary muscle Iris
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Iris Ciliary body Zonule Choroid
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Choroid Loose connective tissue Richly vascularized Pigmented
Several layers
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Ciliary Body Girdles eye anterior to ora serrata
Triangular in shape in section Two components: Ciliary processes Ciliary muscle
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Corneal epithelium Cornea Canal of Schlemm Bulbar conjunctiva Anterior chamber Ciliary muscle Dilator of pupil Sphincter Of pupil Iris Sclera Posterior chamber Ciliary process Ora serrata Lens Vitreous Nuclear zone of lens Hyaloideo-capsular ligament
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Cornea Sphincter pupillae Iris Canal of Schlemm Conjunctiva
Ciliary muscle Ciliary process Sclera Episcleral tissue Episcleral vessels Zonula ciliaris Hyaloidea Lens Ora serrata
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Ciliary processes Form the aqueous humor Ciliary epithelium
Two layers Deep, pigmented layer Superficial non-pigmented layer (represents a non-nervous extension of the nervous portion of the retina anterior to the ora serrata) Stromal cores with numerous capillaries
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Zonular fiber Epithelium Pigment layer Vessel layer Ciliary muscle
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Anterior chamber Aqueous pathway Posterior chamber Vitreous cavity
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Sphincter pupillae Cornea Iris Substantia propria Anterior corneal epithelium Canal of Schlemm Anterior lens epithelium Bulbar conjunctiva Posterior iris epithelium Iridocorneal angle Lens fibers Zonula ciliaris Ciliary processes Equator of the lens Lens capsule Ciliary muscle
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Ciliary muscle Smooth muscle
Three sets of muscle fibers with different orientations Important in accommodation Contraction: releases tension on lens Relaxation: increases tension on lens Parasympathetic innervation
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Cornea Sclera Lens Ciliary muscle Ciliary processes Ora serrata
Anterior chamber Sphincter of pupil Dilator of pupil Sclera Posterior chamber Zonule Lens Ciliary processes Ora serrata
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Cornea Aqueous humor Meridional fibers Circular fibers of ciliary muscle, contracted Zonula fibers (= suspensory ligament) relaxed Ciliary muscle, relaxed Lens, relaxed and permitted to assume greater curvature by its own elasticity (arrow) and pulled forward by the meridional fibers Suspensory ligament pulls (arrow) to flatten lens
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Iris Anterior portion Endothelial surface Underlying connective tissue
Many pigmented cells: chromatophores Amount of pigment determines eye color blue eyes: little or no pigment Gray, green, and brown eyes: increasing pigment Smooth muscle Sphincter: parasympathetic innervation Dilator: sympathetic innervation
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Iris Posterior portion Heavily pigmented in all individuals
Two rows of cuboidal cells
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Sphincter papillae muscle
Stroma of the iris Pigment epithelium Melanocytes
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Retina Inner layer of eye; sensitive portion continues anteriorly only to ora serrata Anterior to ora serrata continues as the non-nervous pars ciliaris Ten named layers
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Ora serrata Pars optica of the retina Macula lutea Fovea centralis
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Pigment epithelium Rods and cones layer External (outer) limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Nerve fiber layer Internal (inner) limiting layer
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Pigment epithelium Layer of rods and cones External limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Optic nerve fiber layer Internal limiting membrane
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Pigmented epithelium Rod photoreceptor Outer limiting membrane Cone photoreceptor Cone cell nuclei Rod cell nucleus Cone pedicle Rod spherule Horizontal cell Bipolar cell MÜller cell nucleus Body of MÜller cell Amacrine cell Ganglion cells Optic nerve fibers Inner limiting membrane Light
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Direction of Light from Lens
Optic nerve fibers to brain Nuclei of ganglion cells Ganglion neuron Müller cell Bipolar neurons Nuclei of bipolar neurons Nuclei of rods and cones Cone Rod Pigmented epithelium
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ILM ONFL GCL Artery IPL INL OPL ONL OLM R&CL PE
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Nerve fiber layer Inner plexiform layer Ganglion cell layer Outer plexiform layer Inner nuclear layer Outer nuclear layer Pigment epithelium Cones and rods Venule Choroid Arteriole Sclera Melanocytes
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Synthesis of melanin by RER, Golgi, and melanosomes. Melanin absorbs light after it has sensitized the receptor. Digestion, by lysosomal enzymes, of photo- receptor fragements phagocytized by pigment epithelial cells. Vitamin A transport and esterification in SER. Ion transport by mito- chondria and membrane invaginations.
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Major retinal cell types
Photoreceptor cells Rod cells Cone cells Bipolar cells Ganglion cells
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Other cell types Horizontal cells Amacrine cells MÜller cells
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Rod cells 130 million Intensity discrimination; night vision
Outer segment: rhodopsin Rod-shaped; membranous stacks of disks contain pigment Inner segment: organelles Nuclear and synaptic regions 100 rods supply each ganglion cell
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Synaptic body Nucleus m Inner segment e Connecting structure (cilium) Outer segment
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Cone cells 6-7 million Color perception and visual acuity
Outer segment: iodopsins Conically shaped; membranous stacks of disks contain pigment Inner segment: organelles Nuclear and synaptic regions 1-10 cones supply each ganglion cell
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Cone cell Inner segment Mitochondria Cilium Outer segment
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Outer segments Cilium Mitochondria Inner segment Cone Rod
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Rod Cell Cone Cell Cilium Basal body Rootlet
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Free- floating disks
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Bipolar cells Extend from outer to inner plexiform layers
Cell bodies lie in inner nuclear layer
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Rod Cone Cone Bipolar cell Vertical pathway Bipolar cell
Outer nuclear layer Outer plexi- form layer Bipolar cell Vertical pathway Bipolar cell Horizontal cell Lateral pathway Inner nuclear layer Amacrine cell Amacrine cell Inner plexi- form layer Ganglion cell layer Ganglion cell Light To optic nerve
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Ganglion cells Give rise to optic nerve
Processes form nerve fiber layer Cell bodies lie in ganglion cell layer
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Rod Cone Cone Bipolar cell Vertical pathway Bipolar cell
Outer nuclear layer Outer plexi- form layer Bipolar cell Vertical pathway Bipolar cell Horizontal cell Lateral pathway Inner nuclear layer Amacrine cell Amacrine cell Inner plexi- form layer Ganglion cell layer Ganglion cell Light To optic nerve
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Other retinal cell types
Horizontal cells Connect groups of cone cells in one area with rods and cones in another area Probably integrate information between rods and cone Amacrine cells Primarily associated with ganglion cells Function: ??
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Rod Cone Cone Bipolar cell Vertical pathway Bipolar cell
Outer nuclear layer Outer plexi- form layer Bipolar cell Vertical pathway Bipolar cell Horizontal cell Lateral pathway Inner nuclear layer Amacrine cell Amacrine cell Inner plexi- form layer Ganglion cell layer Ganglion cell Light To optic nerve
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Other retinal cell types
MÜller cells Retinal glial cells Very large: stretch from internal to external limiting membranes Supportive function
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Pigmented epithelium Rod photoreceptor Outer limiting membrane Cone photoreceptor Cone cell nuclei Rod cell nucleus Cone pedicle Rod spherule Horizontal cell Bipolar cell MÜller cell nucleus Body of MÜller cell Amacrine cell Ganglion cells Optic nerve fibers Inner limiting membrane Light
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Retinal modifications
Macula lutea Lies in direct optic axis ~ 5 mm in diameter Rods gradually disappear Cones become increasingly slender and numerous Fovea centralis: entirely cones ~ 0.6 mm in diameter Clearest vision and greatest visual acuity
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ILM Ganglion cells NFL Fovea centralis GCL IPL INL OPL ONL OLM R&C Cone cells Pigment epithelium
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Normal right eye fundus
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Retinal modifications
Ora serrata Anterior scalloped margin of nervous portion of retina
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Retina with nerve elements
Ciliary extension of retina x150 Epithelium Choroid Sclera Ora serrata
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Retinal modifications
Optic disc Forms the blind spot of the retina Represents the retinal aspect of the optic nerve Optic papilla: portion of disc that is slightly raised due to a heaping up of nerve fibers Physiological cup: small central depression from which central artery and vein of retina emerge
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Central indentation of optic disc
artery Retina Lamina cribrosa Ciliary arteries and nerves Optic nerve Arachnoid Dura
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Refractive media Cornea Lens Zonule (suspensory ligament)
Aqueous humor Vitreous body
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Lens Capsule (a basal lamina; Type IV collagen) Subcapsular epithelium
Homogeneous; zonular fibers attach to it Subcapsular epithelium Single layer of cells on anterior surface Transformed into lens fibers at equator
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Lens Lens substance Aging of lens Lens fibers (cells)
Older ones near center Younger ones more peripheral Aging of lens Gradually loses water: becomes less elastic Result is inability of lens to accommodate
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Anterior pole Capsule Anterior epithelium Newly formed secondary lens fibers Nuclei of lens fibers forming “nuclear bow” Equatorial epithelium Equator Primary lens fibers Posterior pole
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Zonule Numerous fine fibers
Stretch from ciliary body to equator of lens Thin collagen fibers and fibrillin
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Aqueous humor Thin watery substance Produced by ciliary processes
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Vitreous body Clear, transparent gel; 99% water
Fills space posterior to lens Contains collagen-like proteins plus hyaluronic acid
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Accessory structures Eyelids Lacrimal gland
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Eyelid Tarsal plates: dense c.t.; support and strength to eyelid
Skeletal muscle: raises eyelid Thin skin covers outer surface Conjunctiva: a mucous membrane Palpebral: 2 cell layers with goblet cells Bulbar: continuous at limbus with corneal epithelium
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Eyelid Glands Eyelashes: 2-3 rows Sebaceous glands
Meibomian embedded in tarsal plates; inflammation produces a sty Lubricate edges of lids Zeis Associated with hair follicles Sweat glands (glands of Moll) Eyelashes: 2-3 rows
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Skin Conjunctiva Orbicularis muscle Tarsal plate Meibomian glands Eyelashes
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Lacrimal gland Compound tubuloalveolar gland Serous secreting
Many myoepithelial cells
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Eye
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Eye
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Integument Serous tarsal gland Tarsus Orbicularis oculi muscle Conjunctiva Sebaceous tarsal gland (of Meibom) Marginal fascicle of orbicularis oculi muscle Sebaceous and sweat glands Eyelashes
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sclera choroid retina anterior pole posterior pole ciliary body iris lens cornea optic nerve pigment epithelium
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Eye terminology Poles Geometrical axis: anterior to posterior poles
Anterior: central point of corneal curvature Posterior: central point of scleral curvature Geometrical axis: anterior to posterior poles Visual axis: center of pupil to fovea Anatomical equator Meridians: vertical and horizontal
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V.A. A.P. Cornea Posterior chamber Conjunctiva Limbus Anterior chamber Iris Canal of Schlemm Ciliary muscle Lens Medial rectus Zonula ciliaris Ciliary body Ora serrata Lateral rectus Vitreous Lamina cribrosa Sclera Choroid Fovea Retina Dura Optic nerve P.P.
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Visual axis Optical (geometrical) axis Pars iridica Pars ciliaris Ora serrata Pars optica of the retina Macula lutea Fovea centralis
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Nerve fiber layer Ganglion cell layer Internal plexiform layer Internal nuclear layer Direction of light External plexiform layer External nuclear layer Photoreceptor layer Cone Rod Pigment epithelium
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Outer segment Cilium Inner segment Outer rod fiber Cell body Inner rod fiber Rod spherule
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