38 Questions
What is the primary function of the lens?
Refraction of light
How does the lens thin along the equator?
By reducing in thickness
What is the source of energy required for cellular metabolism and replication in the lens?
Anaerobic glycolysis
Which factor prevents oxidative damage and has an anti-cataract effect in the lens?
Ascorbic acid
What is the main function of hexokinase in lens metabolism pathways?
Converts glucose to glucose 6-phosphate
Where is the metabolic activity mainly concentrated in the lens?
Lens equator
What is the effect of aging on lens metabolism?
Decrease in glutathione activity
What leads to the formation of free radicals in the lens?
UV light absorption
What is a common risk factor for developing a posterior subcapsular cataract?
Long-term use of high-dose steroids
Which nutrient source contributes to lens metabolism, apart from the surrounding aqueous humor?
Vitreous humor only
What is the main function of the primary lens fibers?
Produce crystallins
Which part of the lens is responsible for containing primary lens cells and elongating anteriorly as fibers?
Posterior lens epithelium
What is the purpose of the zonules of Zinn in relation to the lens?
Attach the lens to the ciliary body
What is the main characteristic of lens fibers as they age?
They lose their regularity and their nuclei disintegrate
What is the main role of the lens vesicle during development?
Filling up the lumen of the lens
What structure within the eye undergoes a change in shape due to ciliary muscle contraction, leading to accommodation?
Lens
Which region of the lens has the thickest capsule?
Anterior and posterior regions at equator
What is a notable characteristic of primary lens fibers during development?
Are nucleated and contain organelles
What is the correct sequence of divisions in the lens from the earliest to the latest?
Embryonic nucleus, Fetal nucleus, Adult nucleus, Lens cortex
What happens to the lens fibers with age?
They lose their regularity and become less organized
Where is the germinal zone located in the lens?
Just anterior to the equator
What are the main components of lens fibers?
Crystallins, microtubules, and actin proteins
What causes a change in lens power during accommodation?
Contraction of ciliary muscle
Which region of the lens has the thickest capsule?
Anterior pole
What is responsible for attaching the lens to the ciliary body?
"Zonules of Zinn"
What forms the basis of the lens nucleus and cortex?
"Lens fibers"
"Wieger's ligament" is associated with which part of the lens?
"Lens capsule"
"Accommodation" in the eye refers to a change in which part of the eye?
"Lens"
What is the primary protector against oxidative damage in the lens?
Glutathione
What is the primary stimulus that initiates the accommodative mechanism?
Retinal blur
Which type of cataract is characterized by center opacification and susceptibility to oxidative damage due to depleted glutathione?
Nuclear cataract
What is the primary source of nutrients for maintaining lens metabolism?
Aqueous humor
Which ion's increased permeability in aging lenses disrupts the ion balance?
Calcium (Ca2+)
What metabolic process is predominantly responsible for ATP production in the lens?
Anaerobic metabolism
Which type of cataract is most influenced by long-term use of high-dose steroids?
Posterior subcapsular cataract
Which enzyme converts glucose to sorbitol in lens metabolism pathways when hexokinase is not present?
Aldose reductase
'Decrease in soluble lens proteins' is a characteristic of age changes in the lens, primarily affecting which proteins?
'Alpha crystallins'
'Decline of Glutathione' are presumed causative factors for which type of cataract?
'Nuclear cataract'
Learn about the development stages of the crystalline lens, from the formation of the lens placode to the lens vesicle. Understand the differentiation of anterior and posterior lens epithelium during lens development.
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