The EYE SLO (s): You should be able to identify the accessory and internal structures of the eye and explain their function. You should be able to explain how light stimulates the production of nerve impulses, and trace the visual pathways to their destination in the brain. Essential Question: How does our eye detect external stimuli?

The EYE Do Now: List the parts of the eye that you are familiar with.

The EYE Anticipatory Set: Close your eyes and listen….Tell me what you hear. Is sound accentuated? Do you seem to hear more background noise when your eyes are closed? Is it completely dark when you close your eyes? Do you see flashes of light?

The EYE Vocabulary: palpebrae tarsal glands conjunctiva lacrimal glands lacrimal punctae lacrimal canals lacrimal sac lacrimal lake nasolacrimal duct cornea iris ciliary body aqueous humor vitreous humor sclera cornea limbus choroid retina rods cones

External Features of the Eye Palpebrae (eyelids)- separated by the palpebral fissue (intersection of top and bottom lids) Tarsal glands- Supplies oil substance to eye that prevents tear spillage onto the cheek, trapping tears between the oiled edge and the eyeball, and makes the closed lids airtight

External Features of the Eye Conjunctiva- lines the inside of the eyelids and covers the sclera (white part of the eye)- covers most of eye except cornea Sclera-white of the eye Limbus-border of cornea and sclera Cornea is transparent anterior portion

Lacrimal apparatus- system containing the structures for tear production and drainage. lacrimal gland-form/secretes the tears lacrimal gland ducts-convey the fluid to the surface of the eye Tears collect in the lacrimal lake lacrimal punctum-collect tears produced, convey fluid through the lacrimal canals to the lacrimal sac nasolacrimal duct-convey fluid into the cavity of the inner nose carotid plexus -the nerve supply of the lacrimal apparatus Accessory structures of the eye Lacrimal sac

The Anatomy of the Eye

The EYE DO NOW: Why do people cry? Is there a purpose/function of “emotional crying?” Using your laptops, briefly research any current theories on crying.

The EYE SLO (s): You should be able to identify the accessory and internal structures of the eye and explain their function. You should be able to explain how light stimulates the production of nerve impulses, and trace the visual pathways to their destination in the brain. Essential Question: How does our eye detect external stimuli?

The EYE Vocabulary: palpebrae tarsal glands conjunctiva lacrimal glands lacrimal punctae lacrimal canals lacrimal sac lacrimal lake nasolacrimal duct cornea iris ciliary body aqueous humor vitreous humor sclera cornea limbus choroid retina rods cones

Anatomy of the eye-The Orbit Orbit of the Eye

Anatomy of the Eye-Muscles Extrinsic / Extraocular Muscles Act to turn or rotate the eye verticalhorizontaltorsion/twisting

Anterior and Posterior Cavities-Fluids of the Eye

Aqueous humor- transparent, gelatinous fluid similar to plasma, located in anterior cavity Fluids in the eye Produced by ciliary body Circulates within the eye- continually replenished Purpose- -Maintains the intraocular pressure/inflates the eye - Provides nutrition for the avascular ocular tissues (cornea, lens, and anterior vitreous) -Immune support

Fluids in the eye

Vitreous humor fills the posterior cavity tautly hold the eye’s shape and keeps the retina in place not recycled – permanent fluid Fluids in the eye

Checking for Understanding. List the 2 fluid filled chambers of the eye. What is their purpose?

The eye-internal structure Three layers Outer fibrous tunic Sclera and cornea Middle vascular tunic Iris, ciliary body, choroid Inner nervous tunic Retina Suspensory ligaments

Internal structures of the eye Outer Fibrous Tunic- Cornea- transparent front part of the eye lies anterior to the anterior chamber, iris, pupil, and lens refracts light/helps focus incoming light (along with anterior chamber and lens)- primary and most powerful structure to focus light Sclera- Opaque, protective outer layer of the eye composed of tough, fibrous tissue containing collagen (structural protein) and elastic fiber (bundles of proteins in connective tissue that can stretch up to 1.5 times their length, and snap back to their original length when relaxed) site of attachment for the extrinsic eye muscles which rotate the eyeball.

Internal structures of the eye Iris- responsible for controlling the diameter and size of the pupil/amount of light reaching the retina "eye color.“ Ciliary Body- Choroid- Middle Vascular (Blood Vessels) Tunic

The Pupillary Muscles Controls diameter of pupil in response to the intensity of light that falls on the retina

Internal structures of the eye Iris- Ciliary body- attach to suspensory ligaments of lens Ciliary muscles change the shape of the lens for accommodation Ciliary processes produce aqueous humor Choroid- Middle Vascular (Blood Vessels) Tunic

Posterior to the cornea Lens helps focus images Accommodation is the process by which the lens adjusts to focus images Light is refracted as it passes through lens Normal visual acuity is 20/20 Lens

Internal structures of the eye Iris- Ciliary Body- Choroid- network of blood vessels that provides oxygen and nourishment to the outer layers of the retina lies between the retina and the sclera absorbs excessive light Middle Vascular (Blood Vessels) Tunic

Internal Structures of the Eye: Retina Inner Nervous Tunic -- Retina- Outer pigmented portion Inner neural part contains rods and cones (photoreceptors) optic nerve –located the center of the retina - from the center of the optic nerve radiates the major blood vessels of the retina

Internal Structures of the Eye: Retina - Cones –more concentrated at the macula --densely packed at the center of the macula called the fovea -- Color reception -- Less sensitive to light -- High resolution vision/visual acuity

The Organization of the Retina Rods –more numerous (120 million) More sensitive than the cones Dark-adapted vision/motion sensors

Physiology-Photoreception Retinal Pathway Photoreceptors convert light to signals that stimulate a change in the cells membrane potential Signals eventually travel down ganglion cells, to the brain via the optic nerve axons of the ganglion cells form the optic nerve and exit the eye to the brain

Figure Checking for Understanding What is the significance of rods and cones? If you were driving at night, which are responsible for your visual acuity? Which allows you to see color? Follow the path of light from the external environment to the retina. List the structures that the light passes through sequentially.