PowerPoint ® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PART A 8 Special Senses: Eyes

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Eye and Vision Protection for the eye  Most of the eye is enclosed in a bony orbit  A cushion of fat surrounds most of the eye

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Eyelids and eyelashes  Conjunctiva  Lacrimal apparatus  Extrinsic eye muscles

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.1

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Conjunctiva  Membrane that lines the eyelids  Connects to the surface of the eye  Secretes mucus to lubricate the eye

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Lacrimal apparatus  Lacrimal gland—produces lacrimal fluid  Lacrimal canals—drain lacrimal fluid from eyes  Lacrimal sac—provides passage of lacrimal fluid towards nasal cavity  Nasolacrimal duct—empties lacrimal fluid into the nasal cavity

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.2a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.2b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Function of the lacrimal apparatus  Protects, moistens, and lubricates the eye  Empties into the nasal cavity

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Properties of lacrimal fluid  Dilute salt solution (tears)  Contains antibodies and lysozyme

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye  Extrinsic eye muscles  Six muscles attach to the outer surface of the eye  Produce eye movements

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.3a–b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Structures of the Eye Figure 8.3c

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings DCL #13  Draw Color and Label Figure  Also label the Conjunctiva and Orbicularis oculi

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye  Layers forming the wall of the eyeball  Fibrous layer  Outer Tunic  Vascular layer  Middle Tunic  Sensory layer  Inner Tunic

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye Figure 8.4a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye Figure 8.4b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: The Fibrous Layer (Outer)  Sclera  Connective tissue layer (protection)  The “white of the eye”  Cornea  Transparent  Window that focuses light rays  No blood vessels, transplants easily  Optic Nerve  Sends signals to brain  Blood vessels attach there

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Vascular Layer (Middle)  Choroid coat  Rear 5/6 of eye containing blood vessels  Melanin for light absorption  Ciliary body—smooth muscle attached to lens  Lens - central clear body, can change shape  Accomodation - thicken or thins for distance sighting

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Vascular Layer (Middle)  Iris  Regulates amount of light entering eye (opening and closing the pupil)  Colored portion of the eye  Aqueous humor  Fluid secreted from ciliary body  Pupil  Rounded opening in the center of the iris

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer (Inner)  Retina  Contains receptor cells (photoreceptors)  Rods  Cones  Optic disc  Blind spot  Vitreous humor  Jellylike fluid that fills the inside of the eye

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings DCL #14  Draw Color and Label Figure  Label ALL from text

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer  Signals pass from photoreceptors through neurons  Signals leave the retina through the optic nerve  Optic disc (blind spot) is where the optic nerve leaves the eyeball  Cannot see images focused on the optic disc

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer Figure 8.5a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer Figure 8.5b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer Rods  Dim light vision and peripheral vision  All perception is in gray tones

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structure of the Eye: Sensory Layer Cones  Allow for detailed color vision  Fovea centralis—area of the retina with only cones  No photoreceptor cells are at the optic disc, or blind spot

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ophthalmoscope  Instrument used to illuminate the interior of the eyeball  Can detect diabetes, arteriosclerosis, degeneration of the optic nerve and retina

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Posterior Wall of Retina as Seen with Ophthalmoscope Figure 8.8

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pathway of Light Through the Eye  Light must be focused to a point on the retina for optimal vision  The eye is set for distance vision (over 20 feet away)  Accommodation—the lens must change shape to focus on closer objects (less than 20 feet away)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pathway of Light Through the Eye Figure 8.9

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pathway of Light Through the Eye  Image formed on the retina is a real image  Real images are  Reversed from left to right  Upside down  Smaller than the object

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Images Formed on the Retina Figure 8.10

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8.11 Visual Fields and Visual Pathways

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Lens  Cataracts result when the lens becomes hard and opaque with age  Vision becomes hazy  Eventually causes blindness

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Lens Figure 8.7

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings A Closer Look Myopia (nearsighted)  Distant objects appear blurry  Light from those objects fails to reach the retina and are focused in front of it  Results from an eyeball that is too long

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings A Closer Look  Hyperopia (farsighted)  Near objects are blurry while distant objects are clear  Distant objects are focused behind the retina  Results from an eyeball that is too short or from a “lazy lens”

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings A Closer Look  Astigmatism  Images are blurry  Results from light focusing as lines, not points, on the retina due to unequal curvatures of the cornea or lens

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Homeostatic Imbalances of the Eyes  Night blindness—inhibited rod function that hinders the ability to see at night  Color blindness—genetic conditions that result in the inability to see certain colors  Due to the lack of one type of cone (partial color blindness)  Cataracts—when lens becomes hard and opaque, our vision becomes hazy and distorted

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Homeostatic Imbalances of the Eyes  Glaucoma—can cause blindness due to increasing pressure within the eye  Hemianopia—loss of the same side of the visual field of both eyes; results from damage to the visual cortex on one side only