Anatomy And Physiology Of The Eye Flashcards
Describe how the eye converts light rays to a perceived image, naming the principal structures involved in the process.
Light Rays are reflected from an object are focused by the cornea and the lens to produce an upside down image of the object on the light sensitive retina. The retina converts the image to electric impulses, which are carried by the optic nerve to the brains visual cortex, where they produce the sensation of sight.
Name 4 primary structures included in the adnexa.
Orbit, extraocular muscles, eyelids, lacrimal apparatus.
Describe the structure and function of the orbit.
The bony cavity in the skull that houses the globe, extraocular muscles, blood vessels and nerves ; protects the globe from major injury by a rim of bone.
Match the 6 extraocular muscles with their functions
- Medial Rectus. A. Outward rotation
- Lateral Rectus. B. Upward rotation
- Superior Rectus. C. Downward rotation
- Inferior Rectus. D. Inward rotation
- Superior Oblique. E. Excyclotorsion, up and outward
- Inferior Oblique. F. Incyclotorsion, down and inward
- D
- A
- B
- C
- F
- E
What are the 3 functions of the of the eyelids?
To protect the eye from injury, to exclude light, and to aid in lubricating the ocular surface.
Name the three layers of the eyelid.
Outer layer of skin, middle layer of fibrous tissue and muscle, inner layer of tissue (conjunctiva).
What are the 2 principal functions of the Lacrimal Appartatus?
To produce and drain tears.
Give four reasons why tears are important to the functioning of the eye.
Ocular comfort, clear vision, provide moisture and nourish the eye
What is the relationship between the lacrimal gland, lacrimal sac and nasolacrimal duct?
Tears are produced by the lacrimal gland; tears are collected in the lacrimal sac; tears drain into the nasal cavity by means of the nasolacrimal duct.
Name the 3 layers of tear film and their functions.
The outer, oily layer helps prevent evaporation of moisture from the middle, aqueous layer; the middle layer provides moisture, oxygen, and nutrients to the cornea; the inner mucinous layer promotes even spread of the tear film.
What is the principal function of the cornea?
To focus light ray’s reflected to the eye, contributing about two-thirds of the focusing power of the eye.
Match the 5 layers of the corneal tissue with their functions. (Two of the layers preform the same function.)
- Endothelium A. Serves as first line of defense against infection and injury
- Epithelium B. Contributes rigidity
- Bowman membrane C. Acts as an anchor for epithelium
- Descemet membrane D. Maintains proper fluid balance
- Strom
- D
- A
- C
- B
- B
What is the main function of the Sclera?
To protect intraocular contents.
Why is a balance between the inflow and outflow of aqueous humor important?
To maintain intraocular pressure.
Describe the course of aqueous humor into and out of the eye, naming the principal ocular structures involved.
Aqueous humor enters the eye from behind the iris, flows across the back of the iris, through the pupil, and into the anterior chamber; it leaves the anterior chamber at the filtration angle and passes through the trabecular meshwork, the canal of Schlemm, aqueous veins and into the blood vessels.
Name the 3 main structures that make up the uveal tract.
Iris, ciliary body and choroid.
Describe how the pupil dilates and contracts, naming the muscles involved.
Fibers of the dilator muscle that extend from the pupil to the boundary of the iris contract to dilate the pupil; contraction of the sphincter muscle the encircles the pupil makes the pupil smaller.
What is the function of the ciliary processes.
To secrete aqueous humor.
What is the main function of the choroid?
To supply blood (nourishment) to the outer layers of the retina.
Which structure besides the cornea provides the eyes focusing power?
Lens.
What is the physiological process and purpose of accommodation?
The curvature of the lens can change, becoming rounder, to focus images of objects that are closer to the eye.
What is the lens is attached to the ciliary body by transparent fibers called?
Zonules
What is the main function of the vitreous?
To act as a shock absorber for the eye and help maintain the spherical shape of the globe.
The retina includes a photoreceptor layer containing 2 type cells : ______ and _______
Rods and cones
How are the functions of these 2 types of retinal photoreceptors cells different?
Rods are largely responsible for vision in dim light (“night vision”) and for peripheral vision; cones provide sharp central vision and color perception.
Briefly describe how the retina works to produce sight.
The retinal rods and cones receive light rays and, in turn, generate electric (nerve) impulses. These impulses are transmitted to the brain, where the visual messages they carry are converted to the sensation of sight.
The macula contains most of the _____ cells.
Cone
Describe the route of nerve impulses through the retrobulbar visual pathway.
The optic nerve from each eye merge at the optic chiasm. Axon fibers from the nasal retina of each eye cross to the opposite side of the chiasm, while axons from the temporal retina of each eye continue on the same side. The realigned axons emerge from the chiasm as the left and right optic tracts, ending in the left and right lateral geniculate bodies. There the axons synapse (connect) to the optic radiations, which travel to the right and left halves of the visual cortex of the brain.
