1. Special Senses
The eye

2. The Senses General senses of touch Temperature Pressure Painz
General senses of touch
Temperature
Pressure
Pain
Special senses
Smell
Taste
Sight
Hearing Equilibrium

3. 70% of all sensory receptors are in the eyes
The Eye and Vision
70% of all sensory receptors are in the eyes
Each eye has over a million nerve fibers

4. External Anatomy of the Eyez

5. Inert picture 8.1and 8.2

7. Accessory Structures of the Eyez z
Lacrimal apparatus
Produces fluid- contains lysozyme an enzyme that destroys bacteria
Lacrimal canals: drain fluid
Lacrimal sac: provides passage of lacrimal fluid towards nasal cavity
Nasolacrimal duct: empties lacrimal fluid into nasal cavity

9. Internal Anatomy of the Eye (KNOW ALL)
Enter image 8.4

10. Structure of the Eye The wall is composed of three tunics…….
Fibrous layer: outside layer
“Whites of the eye” -sclera & “the window” - cornea
Cornea has many nerve endings
Transplanted without rejection- avascular

11. Structure of the Eye Vascular layer: middle layer Choroid- blood rich
Ciliary body- attached to lens
Iris- makes pupil

12. Structure of the Eye Sensory tunic: inside layer Retina
Pigmented layer- prevent light from bouncing around
neural layer
Rods/cones- photoreceptors
Bipolar cells
Ganglion cells
Leave via optic nerve

13. Neurons of the Retina

14. Blind Spot
Photoreceptors are all over the retina, except where the optic nerve leaves the eyeball
Called optic disk-blind spot
Colorblindness
There are three cone types (blue, green, red)
Lack of all 3- total color blindness
Most common is lack of red or green
X-linked disorders

15. Lens Biconvex crystal-like structure
Held in place by a suspensory ligament attached to the ciliary body

16. Lens Accommodation
Light must be focused to a point on the retina for optimal vision
The eye is set for distance vision (over 20 ft away)
The lens must change shape to focus for closer objects
Eye am hyperlinked!

17. Internal Eye Chamber Fluids
Aqueous humor
Watery fluid found in chamber between the lens and cornea
Similar to blood plasma
Helps maintain intraocular pressure
Provides nutrients for the lens and cornea
Vitreous humor
Gel-like substance behind the lens
Keeps the eye from collapsing
Lasts a lifetime and is not replaced

18. Images Formed on the Retina

19. Visual Pathway Photoreceptors of the retina Optic nerve
Optic nerve crosses at the optic chiasma
Optic tracts
Thalamus (axons form optic radiation)
Visual cortex of the occipital lobe

20. Eye Disorders
Emmetropia: normal eyesight (focuses images correctly on the retina)
Myopia: nearsightedness
Objects are focused on a point in front of the retina
Distant objects appear blurry
Hyperopia: farsightedness
Objects are focused on a point behind the retina
Close objects appear blurry
Astigmatism: unequal curvatures in different parts of the cornea or lens
Cataracts: the lens becomes hard and opaque
Glaucoma: drainage of the aqueous humor is blocked, pressure causes depression of the retina and optic nerve

21. Which is which?
Emmitropia
myopia
hyperopia