15The Eye and VisionAccessory Structures of the EyePowerPoint PresentationEyebrowsEyelidsSlide 7Slide 8ConjunctivaLacrimal ApparatusSlide 11Extrinsic Eye MusclesSlide 13Slide 14Slide 15Structure of the EyeballSlide 17Fibrous LayerSlide 19Vascular Layer (Uvea)Vascular LayerSlide 22Slide 23Sensory Layer: RetinaSlide 25Slide 26The RetinaSlide 28PhotoreceptorsSlide 30Blood Supply to the RetinaSlide 32Internal Chambers and FluidsSlide 34Slide 35Internal Chambers and FluidsSlide 37LensSlide 39PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal CollegeC H A P T E RCopyright © 2010 Pearson Education, Inc.15The Special Senses: Part ACopyright © 2010 Pearson Education, Inc.The Eye and Vision•70% of all sensory receptors are in the eye•Nearly half of the cerebral cortex is involved in processing visual information!•Most of the eye is protected by a cushion of fat and the bony orbitCopyright © 2010 Pearson Education, Inc.Accessory Structures of the Eye•Protect the eye and aid eye function•Eyebrows•Eyelids (palpebrae)•Conjunctiva•Lacrimal apparatus•Extrinsic eye musclesCopyright © 2010 Pearson Education, Inc.Figure 15.1aEyelashesSclera(covered byconjunctiva)Site whereconjunctivamerges withcorneaLateralcommissureIrisMedialcommissureLacrimalcaruncleEyelidEyelidEyebrowPupilPalpebralfissure(a) Surface anatomy of the right eyeCopyright © 2010 Pearson Education, Inc.Eyebrows•Overlie the supraorbital margins•Function in•Shading the eye•Preventing perspiration from reaching the eyeCopyright © 2010 Pearson Education, Inc.Eyelids•Protect the eye anteriorly•Palpebral fissure—separates eyelids •Lacrimal caruncle—elevation at medial commissure; contains oil and sweat glands •Tarsal plates—internal supporting connective tissue sheet •Levator palpebrae superioris—gives the upper eyelid mobilityCopyright © 2010 Pearson Education, Inc.Eyelids•Eyelashes •Nerve endings of follicles initiate reflex blinking•Lubricating glands associated with the eyelids•Tarsal (Meibomian) glands•Sebaceous glands associated with follicles•Ciliary glands between the hair folliclesCopyright © 2010 Pearson Education, Inc.Figure 15.1b(b) Lateral view; some structures shown in sagittal sectionLevator palpebraesuperioris muscleOrbicularis oculi muscleEyebrowTarsal platePalpebral conjunctivaTarsal glandsCorneaPalpebral fissureEyelashesBulbar conjunctivaConjunctival sacOrbicularis oculi muscleCopyright © 2010 Pearson Education, Inc.Conjunctiva•Transparent membrane•Palpebral conjunctiva lines the eyelids•Bulbar conjunctiva covers the white of the eyes •Produces a lubricating mucous secretionCopyright © 2010 Pearson Education, Inc.Lacrimal Apparatus•Lacrimal gland and ducts that connect to nasal cavity•Lacrimal secretion (tears)•Dilute saline solution containing mucus, antibodies, and lysozyme•Blinking spreads the tears toward the medial commissure•Tears enter paired lacrimal canaliculi via the lacrimal puncta•Drain into the nasolacrimal ductCopyright © 2010 Pearson Education, Inc.Figure 15.2Lacrimal glandExcretory ducts of lacrimal glandsLacrimal punctumLacrimal canaliculusNasolacrimal ductInferior meatusof nasal cavityNostrilLacrimal sacCopyright © 2010 Pearson Education, Inc.Extrinsic Eye Muscles•Six straplike extrinsic eye muscles•Originate from the bony orbit•Enable the eye to follow moving objects•Maintain the shape of the eyeball•Four rectus muscles originate from the common tendinous ring; names indicate the movements they promote•Two oblique muscles move the eye in the vertical plane and rotate the eyeballCopyright © 2010 Pearson Education, Inc.Figure 15.3aInferior rectusmuscleInferior obliquemuscleSuperior obliquemuscleSuperior obliquetendonSuperior rectusmuscleLateral rectusmuscle(a) Lateral view of the right eyeCopyright © 2010 Pearson Education, Inc.Figure 15.3bSuperior obliquemuscleCommontendinous ringTrochleaSuperior obliquetendonSuperior rectusmuscle(b) Superior view of the right eyeAxis at centerof eyeMedialrectus muscleInferiorrectus muscleLateralrectus muscleCopyright © 2010 Pearson Education, Inc.Figure 15.3c(c) Summary of muscle actions and innervating cranial nervesLateral rectusMedial rectusSuperior rectusInferior rectusInferior obliqueSuperior obliqueMoves eye laterallyMoves eye mediallyElevates eye and turns it mediallyDepresses eye and turns it mediallyElevates eye and turns it laterallyDepresses eye and turns it laterallyVI (abducens)III (oculomotor)III (oculomotor)III (oculomotor)III (oculomotor)IV (trochlear)Muscle ActionControllingcranial nerveCopyright © 2010 Pearson Education, Inc.Structure of the Eyeball•Wall of eyeball contains three layers• Fibrous•Vascular•Sensory•Internal cavity is filled with fluids called humors•The lens separates the internal cavity into anterior and posterior segments (cavities)Copyright © 2010 Pearson Education, Inc.Figure 15.4aCentral arteryand vein ofthe retinaOptic disc(blind spot)Optic nervePosterior poleFovea centralisMacula luteaRetinaChoroidScleraOra serrata(a) Diagrammatic view. The vitreoushumor is illustrated only in thebottom part of the eyeball.Ciliary bodyCiliary zonule(suspensoryligament)CorneaIrisAnterior polePupilAnteriorsegment (containsaqueous humor)LensScleral venoussinusPosterior segment(contains vitreous humor)Copyright © 2010 Pearson Education, Inc.Fibrous Layer•Outermost layer; dense avascular connective tissue•Two regions: sclera and cornea1.Sclera•Opaque posterior region•Protects and shapes eyeball•Anchors extrinsic eye musclesCopyright © 2010 Pearson Education, Inc.Fibrous Layer2.Cornea: •Transparent anterior 1/6 of fibrous layer•Bends light as it enters the eye•Sodium pumps of the corneal endothelium on the inner face help maintain the clarity of the cornea •Numerous pain receptors contribute to blinking and tearing reflexesCopyright © 2010 Pearson Education, Inc.Vascular Layer (Uvea)•Middle pigmented layer•Three regions: choroid, ciliary body, and iris1. Choroid region•Posterior portion of the uvea•Supplies blood to all layers of the eyeball•Brown pigment absorbs light to prevent visual confusionCopyright © 2010 Pearson Education, Inc.Vascular Layer2.Ciliary body•Ring of tissue surrounding the lens•Smooth muscle bundles (ciliary muscles) control lens shape•Capillaries of ciliary processes secrete fluid •Ciliary zonule (suspensory ligament) holds lens in positionCopyright © 2010