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Chapter 15

Chapter 15. Special Senses: Vision. Accessory structures of the eye. Lacrimal apparatus Lacrimal glands Superior and lateral in each eye Produces tears Several small ducts liberate the tear continually Excretory ducts. Lacrimal Apparatus. Lacrimal canal Medial in each eye Lacrimal sac

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Chapter 15

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  1. Chapter 15 Special Senses: Vision

  2. Accessory structures of the eye • Lacrimal apparatus • Lacrimal glands • Superior and lateral in each eye • Produces tears • Several small ducts liberate the tear continually • Excretory ducts

  3. Lacrimal Apparatus • Lacrimal canal • Medial in each eye • Lacrimal sac • Nasolacrimal duct • Tears • Salt solution • Contains lysozyme and antibodies • Cleanse, protect, moisten and lubricate the eye ball

  4. Accessory structures of the eye • Palpebrae • Lateral canthus • Medial canthus • Caruncle – contains sweat and sebaceous glands

  5. Accessory structures of the eye • Eyelashes • Ciliary glands • Modified sweat glands between the eyelashes • Meibomian or tarsal glands • Posterior to the eyelashes. Secrete oil

  6. Accessory structures of the eye • Sty • Acute inflammation of the ciliary or meibomian gland • Chalazio • Chronic inflammation of the meibomian gland

  7. Accessory structures of the eye • Conjunctiva • Palpebral • Ocular or bulbar • It is a mucosa that secretes mucus • Conjunctivites • Inflamation of the conjunctiva • Extrinsic muscles of the eye • Control eye movement

  8. Internal Anatomy of the eye • Outer fibrous tunic • Dense avascular connective tissue • Sclera • Cornea • Transparent, anterior most portion

  9. Internal Anatomy of the eye • Middle vascular tunic (uvea) • Iris • Colored part of the eye • Smooth muscle acting as a diaphragm • Ciliary body • Ciliary muscles – control the shape of the lens • Ciliary processes – secretes aqueous humor • Suspensory ligaments

  10. Internal Anatomy of the eye • Choroid • Posteriormost part • Contain melanin • Tapetum lucidum (only in animals) • Inner sensory tunic (Retina) • Pigmented layer • Covers the choroid

  11. Internal Anatomy of the eye • Neural layer • Rods – photoreceptors cells for dim light. Perceives gray tones • Cones – photoreceptors cells for color. They need high amount of light • Optic disc – blind spot. Emergency of the optic nerve • Macula lutea – high concentration of cones. • Fovea

  12. Internal Anatomy of the eye • Lens • Held by the suspensory ligaments. Attaches to the ciliary body. • Catarats – lens become opaque and hard

  13. Internal Anatomy of the eye • Anterior segment • Aqueous humor – clear fluid formed by the ciliary process. It provides nutrients for the lens and cornea. • Scleral venus sinus (canal of Schlemm) – absorbs the aqueous humor • Glaucoma – increased intraocular pressure • Posterior segment • Vitreous humor – helps to keep the retina in place

  14. The Sectional Anatomy of the Eye Figure 17.4a, b

  15. Microscopic anatomy of the retina • Pigmented epithelial layer • Located between the choroid and neural layer • Neural layer • Photoreceptors – rods and cones • Bipolar neurons • Ganglion neurons

  16. Microscopic anatomy of the retina

  17. Visual Pathways to the brain • Optic nerve • Optic chiasma • It is the crossing of the fibers of the optic nerve • Optic tract • Thalamus • Optic radiation • Visual cortex – located on the occipital lobe

  18. Visual Tests and Experiments • Blind Spot • When the image fall on the optic disc

  19. Visual Tests and Experiments • Afterimages • Positive afterimage • stimulation of the photoreceptors • Negative afterimage

  20. Visual Tests and Experiments • Refraction of the light rays • Cornea • Lens • Vitreous humor • Accommodation of the lens • Near-point accommodation • Presbiopia – difficult focus for close vision because of decreased lens elasticity

  21. Visual Tests and Experiments • Visual acuity • Snellen chart • Emmetropy • Myopia • Hyperopia • Astigmatism • Irregularity in the curvatures of the lens and/or cornea

  22. Visual Tests and Experiments • Color blindness • Three cone types- red, green and blue • Binocular vision • Three dimensional vision • Accuracy of locating objects • Depth perception • Panoramic vision

  23. Visual Tests and Experiments • Extrinsic muscles of the eye • Convergence • Medial eye movements for near vision • Keep moving objects focused on the fovea

  24. Visual Tests and Experiments • Pupillary reflex • Photopupillary reflex • Constriction of the pupils when the retina is illuminated by a bright light • Intrinsic muscles of the eye • Accommodation pupillary reflex • Change of the pupil diameter for near focus

  25. Eye Dissection • WHOLE EYE • Cornea • Sclera • Optic nerve • Extrinsic muscles

  26. Eye Dissection • FRONTAL CUT • Humors: aqueous, vitreous • Lens • Ciliary body • Iris • Pupil • Choroid • Retina • Posterior cavity

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