1. 7 Lesson 7.1: The Eye Lesson 7.2: The Ear Lesson 7.3: Smell and Taste The Sensory Systems

2. Lesson 7.1 The Eye Chapter 7: The Sensory Systems

3. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. anatomy of the eye – 1 inch (2.5 cm) in diameter –External –Internal vision injuries, diseases, and disorders of the eye The Eye (overview)

4. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. –External 1. Protection –Located in a bony socket of the skull, covered in a fleshy eyelid, and filtered by eyebrows and eyelashes from sweat and dust. 2. Lubrication –Lubricating structures – Tarsal, ciliary, lacrimal glands, and conjunctiva membrane. 3. Movement –Six extrinsic muscles – move the eye in its socket External Structures

5. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. tarsal glands - lubricate ciliary glands - sweat External Structures of the Eye conjunctiva – mucus membrane lacrimal glands - tears (antibodies)

6. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Extrinsic Muscles

7. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Eyeball – hollow chamber, oblong, fluid filled to maintain shape. Humors (fluids) –Aqueous – (smaller) between cornea and iris –Vitreous – (larger) between retina and lens Tissue layers (3) –Sclera – Outer layer, white of the eye, tough & fibrous Cornea – transparent, covers the lens, allows light to pass –Choroid- middle layer, blood vessels, nourish the eye Pupil – opening which light passes Iris – colored portion of eye, controls amount of light entering the eye with two muscles (sphincter & dilator pupillae) –Retina – inner layer, light sensitive nerve endings Rods – activated by dim light Cones – sensitive to bright light and color Internal Structures of the Eye

8. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Lens – located behind the iris - convex on both sides, transparent, flexible - held in place by suspensory ligaments - at rest the eye is focused to clearly see an object at 20 feet - closer objects require the lens to be stretched to change the shape of the lens - the process of contraction of the muscles and making the body of the lens thicker is called Accommodation - after about 40 years of stretching the lens, the muscles lose the ability to accommodate and reading glasses are necessary to see close objects Internal Structures of the Eye

9. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Internal Structures of the Eye

10. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. To “see” an object, light must be reflected off that object, then - pass through the cornea -through the pupil -through the lens -land on the retina -The rod and cone sensory cell will send an impulse -These impulses are collected in the optic nerve -The optic nerves cross at the optic chiasma and exit at the optic tracts - Optic tracts send stimuli to the occipital lobe of the brain for interpretation Vision

11. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Vision Disorders Focal point in front of retina Focal point behind retina Typically occurs age 40 – 45

12. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. conjunctivitis –also known as pink eye – bacterial infection, contagious Cataracts – clouding of the cornea or lens (laser) Glaucoma – increased pressure in the eye (Aq. Humor) macular degeneration – loss of central vision, peripheral is ok diabetic retinopathy – damage to the blood vessels, leakage vitreous floaters – common, chunks of vit. Humor break off and float around Aq. Humor, if too many, then it is problematic Eye Diseases