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</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</p> Signup and view all the answers

    Where is the metabolic activity mainly concentrated in the lens?

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

    What is the effect of aging on lens metabolism?

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

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

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

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

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

    What is the main function of the primary lens fibers?

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

    Which region of the lens has the thickest capsule?

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

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

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

    What happens to the lens fibers with age?

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

    Where is the germinal zone located in the lens?

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

    What are the main components of lens fibers?

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

    What causes a change in lens power during accommodation?

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

    Which region of the lens has the thickest capsule?

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

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

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

    What forms the basis of the lens nucleus and cortex?

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

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

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

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

    <p>Glutathione</p> Signup and view all the answers

    What is the primary stimulus that initiates the accommodative mechanism?

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

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

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

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

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

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

    <p>Anaerobic metabolism</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</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</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'</p> Signup and view all the answers

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

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

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