Lens Flashcards
(21 cards)
What is the function of the lens?
Responsible for fine-tuning an image that is projected onto the retina.
What does the lens need to be functional?
Needs to be transparent,
Have a higher refractive index than the medium its suspended in,
Have flexible refractive surfaces with the proper curvature
What two types of epithelial cells make up the lens?
cubodial cells and elongated fiber cells
what do the epithelial cells of the lens secrete?
the lens capsule
What is the germanitive zone?
Region near the equatorial margin of the lens epithelium, where cells proliferate slowly.
True or False. Posterior Y sutures are upright.
False. posterior = inverted Y, anterior = upright Y
Where do the zonules originate?
Non-pigmented layer of the ciliary epithelium
Where do the zonules insert?
Lens capsule near the equator
How much crystallin does the lens have compared to typical cells?
3x higher
what allows for transparency of the lens?
Regular structure of lens fibers,
The absence of membrane-bound organelles,
Small/uniform extracellular space between fiber cells
True or False. Aphakia is the substitution of the natural crystalline lens with a synthetic lens.
False.
Aphakia: is the absence of the natural crystalline lens, from natural causes or removal.
Pseudophakia: is the substitution of the natural crystalline lens with a synthetic lens.
What is the role of the α-crystallin genes , αA and αB?
Prevent protein aggregation and precipitation
What percent of the lens is made of water?
65% water
What gives lens its birefringent property?
microtubules
What effect does increased cholesterol have on fibers?
Makes it more rigid.
Where did the capillaries at the ANTERIOR part of the lens arise from during development?
Arise from blood vessels of the iris stroma
Where did the capillaries at the POSTERIOR part of the lens arise from during development?
Arise from the hyaloid artery
What can an absences of lens in early embryogenesis lead to?
Absence of corneal endothelium,
Abnormal differentiation of the corneal stroma,
Absence of the iris, ciliary body, and anterior chamber
What protects the lens protects it from oxidative damage?
The low oxygen tension around/within the lens
What process generates free radicals in the lens?
oxidative phosphorylation
True or False. If light is not absorbed, it produces no damage.
True.
