1. The Eye and Vision
Most of eye protected by cushion of fat and bony orbit
Accessory Structures protect eye and aid eye function
Eyebrows, Eyelids, Conjunctiva, Lacrimal apparatus
Extrinsic eye muscles

2. Conjunctiva: Transparent mucous membrane
Produces lubricating mucous secretion
Conjunctiva covers white of eyes but not cornea
Lacrimal Apparatus
Lacrimal glands secrete tears and drain them via ducts into nasolacrimal duct
Lacrimal gland in orbit above lateral end of eye
Tears are dilute saline solution containing mucus, antibodies, and lysozyme
Blinking spreads tears toward medial commissure

3. Six extrinsic eye muscles attach to scleral layer and move eyeball
Originate from bony orbit; insert on eyeball
Enable eye to follow moving objects; maintain shape of eyeball; hold in orbit
Four rectus muscles originate from common tendinous ring; names indicate movements
Superior, inferior, lateral, medial rectus muscles
Two oblique muscles move eye laterally and rotate eyeball
Superior and inferior oblique muscles

4. Structure of Eye:
Outermost layer; dense avascular connective tissue
Two areas: sclera and cornea
1. Sclera--Opaque region
Protects, shapes eyeball; anchors extrinsic eye muscles
Continuous with dura mater of brain posteriorly
2. Cornea--Transparent anterior area
Bends light as it enters eye
Pain receptors contribute to blinking and tearing reflexes
Corneal transplants typically are not rejected by immune system because cornea has no blood vessels

5. 1. Choroid Choroid---Middle pigmented layer
Contains: choroid, ciliary body, and iris
1. Choroid
Supplies blood to all layers of eyeball
Black pigment absorbs light to prevent it scattering within eye which makes focusing impossible
2. Ciliary body
Ring of smooth muscle surrounding lens
Ciliary muscles relax and contract to control lens shape to allow lens to focus light
Capillaries of ciliary processes secrete fluid
Suspensory ligament holds lens in position

6. 3. Iris-anterior to ciliary body
Colored part of eye
Pupil—central opening that regulates light entering eye
Close vision and bright light —pupils constrict
Distant vision and dim light —pupils dilate
Changes in emotional state—pupils dilate when subject matter is appealing or requires problem-solving skills
Intrinsic eye muscles = ciliary muscle and iris

7. Biconvex, transparent, flexible, and avascular
Lens
Biconvex, transparent, flexible, and avascular
Changes shape to precisely focus light on retina
filled with transparent protein crystallin
becomes more dense, convex, less elastic with age
Cataracts (clouding of lens) consequence of aging, diabetes mellitus, heavy smoking, frequent exposure to intense sunlight

8. Innermost Layer: Retina Delicate 2-layered membrane
Outer pigmented layer
Absorbs light and prevents its scattering
Phagocytize photoreceptor cell fragments
Stores vitamin A
Inner Neural layer
Transparent
Composed of 3 types of neurons
Photoreceptors, bipolar cells, ganglion cells
Signals spread from photoreceptors  bipolar cells  ganglion cells
Ganglion cell axons exit eye as optic nerve

9. Optic disc (blind spot) Lacks photoreceptors
The Retina
Optic disc (blind spot)
Lacks photoreceptors
Site where optic nerve leaves eye
Photoreceptors (quarter-billion) of two types
Rods-black and white vision
Cones-color vision

10. Rods Cones Dim light, peripheral vision receptors
More numerous, more sensitive to light than cones
Used for peripheral vision because numbers greatest at periphery
Cones
Receptors for color vision which function better in bright light (daytime vision)
Macula lutea
Mostly cones
Fovea centralis
Tiny pit in center of macula with all cones; best vision

11. Internal Chambers and Fluids
Anterior area contains Aqueous humor
Plasma like fluid continuously formed
Drains via canal of Schlemm (at sclera-cornea junction)
Supplies nutrients and oxygen mainly to lens and cornea but also to retina, and removes wastes
Helps maintain shape and pressure of eye
Glaucoma: blocked drainage of aqueous humor increases pressure and causes compression of retina and optic nerve  blindness

12. Posterior area contains vitreous humor that Transmits light
Supports posterior surface of lens
Holds neural layer of retina firmly against pigmented layer
Contributes to intraocular pressure and maintains shape of eye
As you get older, may get floaters—
caused by age-related changes and/or changes in vitreous consistency  becomes more liquid  causes shrinking and pulling away from interior surface of eye. This can cast shadows on your retina, which you interpret as eye floaters.
If you notice a sudden increase in number of floaters, contact an eye doctor immediately — especially if you see flashes of light or lose your peripheral vision; may be caused by retinal detachment.

13. LABWORK
1. Dissect sheep eye 2. Using eye models and charts, locate the following: sclera, choroid, cornea, retina, iris, pupil, ciliary body, lens, aqueous humor, vitreous body, optic disk, optic nerve. 3. Perform eye tests for visual acuity, astigmatism, and other tests in your lab book, time permitting.

14. The Ear: Hearing and Equilibrium (Balance) Three major areas of ear
External (outer) ear – hearing only
Middle ear (tympanic cavity) – hearing only
Internal (inner) ear – hearing and equilibrium
Receptors for hearing and balance respond to separate stimuli

15. External Ear
Auricle (pinna)
Funnels sound waves into auditory canal
Sound is form of energy transmitted in waves; different sounds have different wavelengths
External acoustic meatus (auditory canal)
Short tube lined with skin ceruminous glands
Transmits sound waves to eardrum

16. Tympanic membrane (eardrum)
Boundary between external and middle ears
Connective tissue membrane that vibrates in response to sound
Transfers sound energy to bones of middle ear
Middle Ear
Small, air-filled, mucosa-lined cavity in temporal bone
Eardrum at lateral border and medially is bony wall containing oval (vestibular) and round (cochlear) windows

17. Eustachian or Pharyngotympanic (auditory) tube—connects middle ear to nasopharynx
Equalizes pressure in middle ear cavity with external air pressure
Ear Ossicles
Three small bones in tympanic cavity: the malleus (hammer), incus (anvil), and stapes (stirrup)
Suspended by ligaments and joined by synovial joints
Transmit vibratory motion of eardrum to oval window

18. Inner Ear (has sound and equilibrium receptors)
Bony labyrinth --filled with perilymph
Three regions: vestibule, semicircular canals, and cochlea
Membranous labyrinth -filled with endolymph
Series of membranous sacs and ducts
Vestibular apparatus
Equilibrium receptors in semicircular canals and vestibule
Vestibular receptors monitor static equilibrium
Semicircular canal receptors monitor dynamic equilibrium

19. Vestibule
Central cavity of bony labyrinth
Contains two membranous sacs
Saccule: continuous with cochlear duct
Utricle: continuous with semicircular canals
Sacs responsible for static or linear equilibrium
Maculae contain equilibrium receptor regions
Responds to gravity and changes in position of head

20. Semicircular Canals
Three canals (anterior, lateral, and posterior) lie in three planes of space
Membranous ducts line canals and communicate with utricle
Ampulla of each canal houses equilibrium receptor region called crista ampullaris
Receptors respond to angular (rotational) movements of head

21. spiral, conical, bony chamber; size of split pea
The Cochlea--hearing
spiral, conical, bony chamber; size of split pea
Extends from vestibule
Coils around bony pillar
Contains cochlear duct, which contains Organ of Corti (spiral organ)
"roof" of cochlear duct is vestibular membrane
External wall secretes endolymph
"Floor" of cochlear duct composed of basilar membrane which supports organ

22. Auditory Processing
Pitch perceived by impulses from specific hair cells in different positions along basilar membrane
Loudness detected by increased numbers of action potentials that result when hair cells experience larger deflections
Localization of sound depends on relative intensity and relative timing of sound waves reaching both ears

23. Sensory receptors for static equilibrium
Maculae
Sensory receptors for static equilibrium
One in each saccule wall and one in each utricle wall
Monitor position of head in space, necessary for control of posture
Respond to linear acceleration forces, but not rotation
Contain supporting cells and hair cells
Stereocilia and kinocilia are embedded in otolith membrane studded with otoliths (tiny CaCO3 stones)

24. The Ear: 1. Find the following structures in your lab book and the human ear models: Pinna, pharyngotympanic (auditory) tube, Tympanic membrane (eardrum), malleus, Incus, Stapes, Cochlea, Vestibule, Semicircular canals, Auditory canal, Round/oval windows, Vestibulocochlear nerve. 2. View slide of the cochlea and note the three fluid-filled chambers and the organ of Corti. 3. Perform hearing/balance tests in lab book.