36 Questions
Which part of the lens invaginates to form the lens pit?
Lens placode
On what day those the lens form during embryology?
27th day
What differentiates into primary lens cells and elongates anteriorly as fibers, toward the anterior lens epithelium to fill up the lumen?
Posterior lens epithelium
What do young outer fibers of the lens contain?
Nuclei and organelles
Where is the germinative zone located?
Just anterior to the equator
Which part of the lens forms the fetal nucleus?
Anterior lens epithelium
What do Y inverted sutures denote during slit lamp examination?
Boundaries of the fetal nucleus
What is the main mass of the lens composed of?
Primary and secondary lens fibers
What can cause a change in the shape of the lens, increasing its dioptric power for accommodation?
Ciliary muscle contraction
What part of the eye is attached to the anterior vitreous face by Wieger’s ligament?
Lens capsule
What is the anterior radius of curvature of the lens?
8-14 μm
Where are Y inverted sutures seen during slit lamp examination?
Fetal nucleus
What is the primary function of the lens?
To refract light
What is the source of the energy required for cellular metabolism and cellular replication in the lens?
Anaerobic glycolysis
What is the primary protector against oxidative damage in the lens?
Glutathione
What is the effect of age changes on soluble lens proteins (alpha crystallins)?
Decrease in soluble lens proteins
Which type of cataract is located just beneath the posterior capsule and impacts vision early?
Posterior subcapsular cataract
What are the risk factors for cataract development according to the text?
High dose of steroids
What is the primary cause of blindness according to the text?
Cataract
Which of the following mechanisms is presumed to be causative of cataracts?
Protein modification
What does a nuclear cataract mainly consist of?
Embryonic fetal or adult nucleus
What is the primary effect of ascorbic acid in relation to oxidative stress of the lens?
Prevents oxidative damage (anti-cataract effect)
What does anaerobic glycolysis serve as a source for in lens metabolism?
Maintaining ATP activity in epithelial cells and newer fibers near the equator
What is the impact of age changes on glutathione activity?
Decrease in glutathione activity
What is the refractive power of the unaccommodated lens?
20 D
Which part of the lens contains a higher concentration of crystallins?
Nucleus
What is the approximate thickness of the thinnest region of the lens at the posterior pole?
3 μm
Which part of the lens is responsible for secretion of the anterior capsule throughout life?
Anterior lens epithelium
What is the name of the elastic acellular envelope that allows passage of small molecules into and out of the lens?
Lens capsule
Which part of the lens contains fibers formed after sexual maturation?
Adult nucleus
What is the primary function of the zonules of Zinn?
To attach the lens to the ciliary body
What happens to the diameter of the ciliary ring in an emmetropic eye when viewing a distant object?
It increases
During accommodation, what happens to the anterior chamber of the eye?
It becomes shallower
What change occurs in the lens shape during accommodation?
The lens becomes more flattened
What do lens fibers lose as they become compacted in the nucleus?
Cellular organelles and nuclei
Where do zonules of Zinn arise from?
Basement membrane of the nonpigmented ciliary epithelium
Test your knowledge about the development of the crystalline lens in the human eye. From the formation of the lens placode to the separation from the surface ectoderm, this quiz covers key stages in lens development.
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