Corneal Histology Quiz
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Questions and Answers

What contributes to the formation of the corneal stroma and the corneal endothelium?

  • Surface ectoderm
  • Neural crest cells (correct)
  • Mesenchymal cells
  • Bowman's layer

What is the radius of curvature of the anterior transparent sphere of the cornea?

  • 6mm
  • 10mm
  • 8mm (correct)
  • 12mm

What is the refractive power of the cornea?

  • 75D
  • 30D
  • 45D (correct)
  • 60D

What is the central cornea thickness?

<p>0.53mm (D)</p> Signup and view all the answers

From the front, how does the cornea appear?

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

What is the radius of curvature of the central cornea's anterior surface?

<p>7.8mm (C)</p> Signup and view all the answers

What is the diameter of the globe in the anteroposterior direction?

<p>24mm (C)</p> Signup and view all the answers

Which layer of the cornea is produced by the corneal endothelium?

<p>Descemet's layer (A)</p> Signup and view all the answers

What contributes to the formation of the corneal epithelium?

<p>Surface ectoderm (B)</p> Signup and view all the answers

What is the refractive power of the cornea in diopters (D)?

<p>45D (B)</p> Signup and view all the answers

What is the primary function of the cornea?

<p>To refract light (A)</p> Signup and view all the answers

Which layer of the cornea contains a thickened area of collagenous connective tissue known as Schwalbe’s line?

<p>Descemet’s layer (A)</p> Signup and view all the answers

What is the average cell density of the corneal endothelium in adults?

<p>2500 cells/mm2 (A)</p> Signup and view all the answers

Which layer of the cornea is responsible for regulating water and ion flow from the aqueous humor?

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

Where are the corneal nerves located?

<p>Epithelium, anterior stroma/Bowman’s layer, and midstroma (D)</p> Signup and view all the answers

What is the total refractive power of the eye, and how much of it is attributable to the cornea?

<p>60-65 D, 43 to 48 D (B)</p> Signup and view all the answers

Which layer of the cornea serves as a leaky barrier between the corneal stroma and the anterior chamber?

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

What happens to the corneal endothelial cells with age?

<p>They wear out and neighboring cells change shape and size (B)</p> Signup and view all the answers

Which nerve innervates the cornea?

<p>Ophthalmic nerve (V1) (D)</p> Signup and view all the answers

What factors affect the amount of corneal refraction?

<p>Curvature of the anterior corneal surface, change in refractive index, corneal thickness (A)</p> Signup and view all the answers

What is the approximate thickness of Bowman's layer in the cornea?

<p>8-14 $\mu$m (C)</p> Signup and view all the answers

Where are the stem cells responsible for continuous replacement of the corneal epithelium located?

<p>Around the corneal periphery (D)</p> Signup and view all the answers

What is the main function of keratocytes in the cornea?

<p>Synthesize collagen and extracellular matrix components (A)</p> Signup and view all the answers

Which layer of the cornea is responsible for attracting water to create precise spacing between the lamellae?

<p>Ground substance in the stroma (A)</p> Signup and view all the answers

Which layer of the cornea is the true basement membrane of the endothelium?

<p>Descemet's membrane (A)</p> Signup and view all the answers

What contributes to the transparency of the corneal stroma?

<p>Regular arrangement of stromal component and small diameter of the fibrils (A)</p> Signup and view all the answers

Which layer of the cornea is the principal refracting component of the eye?

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

What is the main function of the corneal endothelium?

<p>Maintain stromal hydration (B)</p> Signup and view all the answers

Which layer of the cornea is composed of collagen fibers, keratocytes, and extracellular ground substance?

<p>Corneal stroma (D)</p> Signup and view all the answers

What is the approximate thickness of the corneal epithelium?

<p>50 $\mu$m (C)</p> Signup and view all the answers

Mention the type of junctions that are seen in the corneal epithelium

<p>Zonula occludents(tigh junctions) Adherens junctions Desmosomes(macula adherence) Gap junctions</p> Signup and view all the answers

Which cells are the source for renewal of the corneal basal cell layer?

<p>Stem cells (D)</p> Signup and view all the answers

Where does migration of the basal cells occur?

<p>From the periphery of the cornea toward the center (A)</p> Signup and view all the answers

Since the bowman's layer is prenatally produced, it cannot regenate. What cells can replace it though?

<p>Epithelial cells or stromal scar tissue (D)</p> Signup and view all the answers

What is the radius of the sclera?

<p>12 (D)</p> Signup and view all the answers

Where does the cornea fit?

<p>Scleral foramen (B)</p> Signup and view all the answers

The cornea has an elliptic shape

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

What covers the anterior and posterior surface of cornea?

<p>Tear film in anterior and aqueous filled anterior chamber in posterior (A)</p> Signup and view all the answers

The periphery of the cornea is continous with the conjunctiva and the sclera

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

How many cells thick is the epithelium?

<p>5-7 (C)</p> Signup and view all the answers

What type of cells does the epithelium and its surface layer have?

<p>Stratified non-keratinized epithelium (D)</p> Signup and view all the answers

Which type of cells in the epithelium have a convex anterior surface and concave posterior surface?

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

Which layer of the cornea is acellular?

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

Which of the corneal layers is also known as substantia propia?

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

Which of the layers is known as the true basement membrane?

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

What type of cells are seen in the endothelium?

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

Flashcards

Cornea

The clear, dome-shaped outer layer of the eye that helps focus light.

Anterior corneal surface

The curved outer surface of the cornea.

Refractive power of the cornea

The ability of the cornea to bend light rays.

Corneal epithelium

The frontmost layer of the cornea, made of stratified squamous epithelium.

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Stem cells in corneal epithelium

Specialized cells in the corneal epithelium that help repair and regenerate the layer.

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Bowman's layer

A thin, clear layer beneath the corneal epithelium that provides strength and structure.

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Corneal stroma

The thickest layer of the cornea, made of collagen fibers and other substances arranged in a precise pattern.

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Keratocytes

Cells within the corneal stroma that produce collagen and other components.

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Corneal endothelium

The innermost layer of the cornea, a thin membrane responsible for regulating water and ion flow.

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Descemet's membrane

A layer of connective tissue produced by the corneal endothelium, located beneath the endothelium.

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Radius of curvature of the cornea

The radius of curvature of the anterior corneal surface, a measure of how much the cornea curves.

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Central corneal thickness

The average thickness of the cornea in the center.

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Shape of the cornea

The appearance of the cornea when viewed from the front.

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Anteroposterior diameter of the eye

The average diameter of the eye from the front to the back.

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Ophthalmic nerve (V1)

The nerve that innervates the cornea, responsible for sensation.

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Factors affecting corneal refraction

The factors that influence how much the cornea bends light.

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Cell junctions in corneal epithelium

The specialized junctions between cells in the corneal epithelium, responsible for maintaining its structure and integrity.

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Stem cell location in corneal periphery

The location where the stem cells for the corneal epithelium are found.

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Basal cells

The cells that continuously replace the corneal epithelium.

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Renewal of corneal epithelium

The process of replacing the corneal epithelium.

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Bowman's layer regeneration

The reason why Bowman's layer cannot regenerate.

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Bowman's layer replacement

The tissue that can replace Bowman's layer after injury.

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Corneal endothelial cell aging

The gradual decline in corneal endothelial cell function with age.

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Corneal endothelium and hydration

The role of the corneal endothelium in maintaining corneal hydration.

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Corneal stroma and refraction

The function of the corneal stroma in refractive power.

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Epithelial thickness

The approximate thickness of the corneal epithelium.

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Corneal location

The part of the eye where the cornea is situated.

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Corneal shape

The shape of the cornea.

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Corneal coverings

The layers that cover the cornea.

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Epithelial cell layers

The approximate number of cell layers in the corneal epithelium.

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Cell type in corneal epithelium

The type of cells found in the corneal epithelium and the surface layer.

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Wing cells

The unique shape of the epithelial cells in the corneal epithelium.

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Acellular corneal layer

The layer of the cornea that does not contain any cells.

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Corneal layer with an alternative name

The layer of the cornea that is also known as a specific name.

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Basement membrane of the cornea

The corneal layer that acts as the true basement membrane.

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Corneal endothelial cell type

The type of cells found in the corneal endothelium.

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Study Notes

Corneal Histological Features

  • The cornea is the principal refracting component of the eye and is approximately 71mm in size.
  • It is transparent and avascular, providing optimal light transmittance.
  • The cornea has five layers: epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium.
  • The corneal epithelium is the outermost layer and is 50 μm thick, with three different layers: surface layer, wing cells, and basal layer.
  • The corneal epithelium undergoes continuous replacement through cell proliferation and migration, with stem cells located around the corneal periphery.
  • Bowman's layer is an acellular dense layer composed of collagen fibrils and is approximately 8-14 μm thick.
  • The corneal stroma, also known as Substantia Propria, is approximately 500 μm thick and composed of collagen fibers, keratocytes, and extracellular ground substance.
  • Collagen fibers in the corneal stroma form parallel layers called lamellae, contributing to corneal transparency.
  • Keratocytes are fibroblasts of the cornea that synthesize collagen and extracellular matrix components.
  • The ground substance in the corneal stroma contains proteoglycans, which attract water to create precise spacing between the lamellae, contributing to stromal hydration and transparency.
  • Descemet's membrane is the true basement membrane of the endothelium and consists of two laminae, thickening throughout life.
  • The very regular arrangement of the stromal component and the small diameter of the fibrils contribute to stromal transparency.

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The Cornea PDF

Description

Test your knowledge of corneal histological features with this quiz. Explore the five layers of the cornea, including the epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. Learn about the composition of each layer, the role of keratocytes, and the factors contributing to corneal transparency.

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