Anatomy 2 Exam 1

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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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