Anatomy & Physiology - Eye & Vision 1 Flashcards
Name the three layers of the eye ball
- Fibrous 2. Vascular 3. Inner (Retina)
Name the two parts of the fibrous layer.
- Cornea = anterior 1/6 2. Sclera = posterior 5/6
What is the external sheet of the cornea made of?
Stratified squamous epithelium
What is the corneal endothelium (deep epithelial sheet) composed of?.
Simple squamous endothelium
List two features of the cornea that allow it to keep its transparency
- No blood vessels 2. Active sodium pumps in corneal endothelium
What is the constant pressure in the cornea
There is a constant intraocular pressure pushing aq humour into stroma
What is the benefit of the endothelial pump
Maintains clarity of cornea by keeping water content low.
What is the function of the sclera?
Provides anchoring site for extrinsic eye muscles
Name the three parts of the vascular layer.
- Choroid 2. Ciliary body 3. Iris
What is the function of the choroid?
- Supplies blood to all 3 layers of the eye. 2. Melanocytes absorb light and prevent it from scattering.
What is the function of the iris?
Controls diameter of pupil regulating amount of light admitted to eye.
What muscles control the iris functions
- Dilator pupillae - radial muscle 2. Sphincter pupillae - circular muscle
List the two functions of the ciliary body
- Smooth muscle bundles control shape of lens 2. Produces aqueous humor.
Describe the vascularity of the retina.
- Inner 2/3 supplied by central artery and central vein of the artery. 2. Outer 1/3 - supplied by blood vessels in choroid
Describe the histology of the fovea centralis
- Avascular. 2. Contains only cones. 3. Outer layers of retina displaced - allows light to pass directly to cones.
How does the eye focus an image on the retina?
Ciliary muscles and ciliary zonule change shape of lens.
What is the anatomical positioning of the lens
Sits behind the pupil suspended from ciliary body by sensory ligaments in a 360 degree fashion
Describe the structure of the lens
- Avascular 2. Biconvex 3. Enclosed in thin, elastic capsule. 4. Flexible 5. Transparent
Why is it harder for eye to focus as we get older age?
- Cuboidal cells in lens ==> new lens fibers continually 2. Lens gets larger, denser, more convex, and less elastic.
What structure separates the anterior and posterior segments of the eye?
The lens.
Describe the structure of the anterior segment?
- Divided into 2 chambers - anterior and posterior - by iris. 2. Filled with aqueous humor.
Name the two muscles of the eyelid and describe their functions.
- Levator palpebrae superioris - elevates to open 2. Obicularis oculi - contracts to close
What is the conjuctivia
Membrane that lines the inside of the eye lid and the sclera infront - doesn’t extend over cornea
True or False. The mucous membrane that lines the eyelids and is reflected over the anterior surface of the eyeball is the conjunctiva.
True
True or False. Vitamin A needed by the photoreceptor cells is stored by the cells of the retina pigmented layer.
False. Stored by the retinals.
True or False. The optic disc is forms a blind spot where the optic nerve leaves the eyeball.
True
True or False. Ciliary muscles are considered voluntary, skeletal muscle.
False. Ciliary muscles are controlled by parasympathetic fibers of the oculomotor nerve.
True or False. The neural layer of the retina prevents excessive scattering of light within the eye.
False. The pigmented layer prevents excessive scattering of light.
True or False. Light passes through the entire thickness of the neural layer of the retina to excite the photoreceptors.
True.