36 Questions
What is the embryonic nucleus composed of?
Primary lens cells
What happens to the nuclei of young outer lens fibers as they age?
They disintegrate and lose their nuclei and organelles
What contributes to the remaining nuclei after the formation of the embryonic nucleus?
Anterior lens epithelium
What denotes the boundaries of the fetal nucleus during slit lamp examination?
Y inverted sutures
Where is the lens located in the eye?
Posterior to the vitreous chamber
Which part of the lens forms new fiber cells?
Lens epithelium
What causes a change in the shape of the lens, increasing its dioptric power for accommodation?
Contraction of the ciliary muscle
What is the name of the area of nonadhesion between the vitreous and lens?
Retrolental space of Berger
What are the dimensions of the anterior radius of curvature?
8-14 μm
Which part of the lens is attached to the anterior vitreous face by Wieger’s ligament?
Posterior lens surface
What part of the lens forms the basis of the nucleus and cortex?
Lens fibers
Where is the germinative zone located in relation to the equator?
Just anterior to it
What is the refractive power of the unaccommodated lens?
20 D
Where is the nucleus of the lens located?
In the embryonic nucleus
What are the dimensions of a lens fiber in cross section?
3 by 9 μm
Which region of the lens contains the thickest fibers?
Equator
What contributes to the gradient refractive index in lens fibers?
Water-soluble proteins
What is the shape of the lens fibers when viewed in cross section?
Hexagonal
What is responsible for changing the lens shape during accommodation?
Relaxation of ciliary muscle
Which structure attaches the lens to the ciliary body?
"Zonules of Zinn"
What is the refractive index of the lens nucleus?
$1.50$
Which region of the lens contains the thinnest fibers?
Posterior pole
What is responsible for maintaining the structure of lens fibers?
Microtubules and filaments
What happens to lens fibers as growth continues?
They become larger and compacted as insoluble protein in the nucleus
What is the primary function of the lens?
Refraction of light
Which source provides nutrients to the lens?
Aqueous humor
What is the primary protector against oxidative damage in the lens?
Glutathione
What is the main cause of loss of accommodative ability in aging?
Changes in ciliary body
What is the greatest cause of blindness related to the lens?
Cataract
Which type of cataract is known for its yellow coloration?
Nuclear cataract
What is the main risk factor for developing a posterior subcapsular cataract?
Long-term use of high-dose steroids
What mechanism is presumed causative for cataract development?
Fluid and ion imbalance
Where does the metabolic activity mostly occur in the lens?
Anterior epithelium
Which type of light absorption can produce oxidative changes causing the formation of free radicals?
Ultraviolet (UV) light absorption
What is the primary function of the lens metabolism?
Regulation of water movement to create the correct constituents optically
What causes cellular damage in the lens due to excess sorbitol?
Osmotic gradient favoring water movement into the lens
Learn about the development of the crystalline lens in the 27th day of development, including the formation of the lens placode, lens pit, and lens vesicle. Understand the composition of the lens vesicle and its significance in optic development.
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