Crystalline Lens Development

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Questions and Answers

What is the primary function of the lens?

  • Refraction of light (correct)
  • Absorption of light
  • Scattering of light
  • Dispersion of light

How does the lens thin along the equator?

  • By elongating the fibers
  • By reducing in thickness (correct)
  • By reducing in transparency
  • By increasing in density

What is the source of energy required for cellular metabolism and replication in the lens?

  • Lipid breakdown
  • Anaerobic glycolysis (correct)
  • Protein synthesis
  • Aerobic respiration

Which factor prevents oxidative damage and has an anti-cataract effect in the lens?

<p>Ascorbic acid (C)</p> Signup and view all the answers

What is the main function of hexokinase in lens metabolism pathways?

<p>Converts glucose to glucose 6-phosphate (A)</p> Signup and view all the answers

Where is the metabolic activity mainly concentrated in the lens?

<p>Lens equator (A)</p> Signup and view all the answers

What is the effect of aging on lens metabolism?

<p>Decrease in glutathione activity (C)</p> Signup and view all the answers

What leads to the formation of free radicals in the lens?

<p>UV light absorption (D)</p> Signup and view all the answers

What is a common risk factor for developing a posterior subcapsular cataract?

<p>Long-term use of high-dose steroids (C)</p> Signup and view all the answers

Which nutrient source contributes to lens metabolism, apart from the surrounding aqueous humor?

<p>Vitreous humor only (A)</p> Signup and view all the answers

What is the main function of the primary lens fibers?

<p>Produce crystallins (B)</p> Signup and view all the answers

Which part of the lens is responsible for containing primary lens cells and elongating anteriorly as fibers?

<p>Posterior lens epithelium (C)</p> Signup and view all the answers

What is the purpose of the zonules of Zinn in relation to the lens?

<p>Attach the lens to the ciliary body (B)</p> Signup and view all the answers

What is the main characteristic of lens fibers as they age?

<p>They lose their regularity and their nuclei disintegrate (A)</p> Signup and view all the answers

What is the main role of the lens vesicle during development?

<p>Filling up the lumen of the lens (D)</p> Signup and view all the answers

What structure within the eye undergoes a change in shape due to ciliary muscle contraction, leading to accommodation?

<p><strong>Lens</strong> (A)</p> Signup and view all the answers

Which region of the lens has the thickest capsule?

<p>Anterior and posterior regions at equator (D)</p> Signup and view all the answers

What is a notable characteristic of primary lens fibers during development?

<p>Are nucleated and contain organelles (C)</p> Signup and view all the answers

What is the correct sequence of divisions in the lens from the earliest to the latest?

<p>Embryonic nucleus, Fetal nucleus, Adult nucleus, Lens cortex (B)</p> Signup and view all the answers

What happens to the lens fibers with age?

<p>They lose their regularity and become less organized (B)</p> Signup and view all the answers

Where is the germinal zone located in the lens?

<p>Just anterior to the equator (A)</p> Signup and view all the answers

What are the main components of lens fibers?

<p>Crystallins, microtubules, and actin proteins (A)</p> Signup and view all the answers

What causes a change in lens power during accommodation?

<p>Contraction of ciliary muscle (D)</p> Signup and view all the answers

Which region of the lens has the thickest capsule?

<p>Anterior pole (D)</p> Signup and view all the answers

What is responsible for attaching the lens to the ciliary body?

<p>&quot;Zonules of Zinn&quot; (C)</p> Signup and view all the answers

What forms the basis of the lens nucleus and cortex?

<p>&quot;Lens fibers&quot; (B)</p> Signup and view all the answers

"Wieger's ligament" is associated with which part of the lens?

<p>&quot;Lens capsule&quot; (C)</p> Signup and view all the answers

"Accommodation" in the eye refers to a change in which part of the eye?

<p>&quot;Lens&quot; (A)</p> Signup and view all the answers

What is the primary protector against oxidative damage in the lens?

<p>Glutathione (A)</p> Signup and view all the answers

What is the primary stimulus that initiates the accommodative mechanism?

<p>Retinal blur (C)</p> Signup and view all the answers

Which type of cataract is characterized by center opacification and susceptibility to oxidative damage due to depleted glutathione?

<p>Nuclear cataract (C)</p> Signup and view all the answers

What is the primary source of nutrients for maintaining lens metabolism?

<p>Aqueous humor (B)</p> Signup and view all the answers

Which ion's increased permeability in aging lenses disrupts the ion balance?

<p>Calcium (Ca2+) (D)</p> Signup and view all the answers

What metabolic process is predominantly responsible for ATP production in the lens?

<p>Anaerobic metabolism (A)</p> Signup and view all the answers

Which type of cataract is most influenced by long-term use of high-dose steroids?

<p>Posterior subcapsular cataract (B)</p> Signup and view all the answers

Which enzyme converts glucose to sorbitol in lens metabolism pathways when hexokinase is not present?

<p>Aldose reductase (D)</p> Signup and view all the answers

'Decrease in soluble lens proteins' is a characteristic of age changes in the lens, primarily affecting which proteins?

<p>'Alpha crystallins' (B)</p> Signup and view all the answers

'Decline of Glutathione' are presumed causative factors for which type of cataract?

<p>'Nuclear cataract' (B)</p> Signup and view all the answers

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