Anatomy 1 Final Info for Cornea and Sclera
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Questions and Answers

What is the radius of curvature of the anterior surface of the cornea?

  • 7.8 mm (correct)
  • 11mm
  • 12mm
  • 6.5mm

    • Which cells contribute to the formation of the corneal stroma and corneal endothelium?

  • Surface endoderm cells
  • Neural ectoderm cells
  • Surface ectoderm cells
  • Neural crest cells (correct)

    • What is the refractive power of the cornea?

  • 45D (correct)
  • 40D
  • 50D
  • 60D

    • What is the central cornea thickness?

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

    Which blood source does NOT supply blood to the cornea?

    <p>Long anterior ciliary arteries</p> Signup and view all the answers

    What type of cells make up the corneal epithelium?

    <p>Stratified squamous non-keratinized cells</p> Signup and view all the answers

    What type of cells join the basal layer of the epithelium to Bowman's membrane?

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

    Which layer of the cornea contains Na/K ATP pumps to regulate water and ion flow?

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

    Which corneal layers CANNOT regenerate?

    <p>Bowman's membrane and Endothelium</p> Signup and view all the answers

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

    <p>1000-2000 cells/mm2</p> Signup and view all the answers

    Which nerve innervates the cornea?

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

    Where are corneal nerves located?

    <p>Epithelium and Bowman’s layer</p> Signup and view all the answers

    What is the circular structure at the termination of the Descemet’s membrane in the limbus called?

    <p>Schwalbe’s line</p> Signup and view all the answers

    What types of cells make of the corneal endothelium?

    <p>Simple squamous cells</p> Signup and view all the answers

    What forms a leaky barrier between the corneal stroma and the anterior chamber?

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

    What is the approximate thickness of the corneal epithelium?

    <p>30 μm</p> Signup and view all the answers

    Which layer of the cornea is responsible for corneal epithelial renewal?

    <p>Bowman’s layer</p> Signup and view all the answers

    What is the composition of Bowman’s layer?

    <p>Acellular dense layer of random collagen fibrils</p> Signup and view all the answers

    Which component of the corneal stroma contributes to its relatively high hydration?

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

    How are corneal endothelial cells linked together by?

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

    What passes through Bowman’s layer in the cornea?

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

    What is the approximate size of the cornea?

    <p>71mm</p> Signup and view all the answers

    What is the turnover time of corneal epithelial renewal?

    <p>7 days</p> Signup and view all the answers

    Which layer of the cornea is constantly produced and thickens throughout life?

    <p>Descemet’s membrane</p> Signup and view all the answers

    What is the composition of the corneal stroma?

    <p>Collagen fibers and keratocytes</p> Signup and view all the answers

    Of the total refractive power between 60-65, what amount is attributable to the cornea?

    <p>43-48 D</p> Signup and view all the answers

    Which layer of the corneal epithelium contains gap junctions?

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

    Which answer is correct regarding the corneal epithelium developement?

    <p>6th week from surface ectoderm</p> Signup and view all the answers

    As we age, the cell density of our corneal endothelium cells increases over time.

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

    There are corneal nerves found in the Descemet's layer and endothelium.

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

    When the corneal nerves pass through Bowman's clayer, they become un-myelinated.

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

    What is the primary contributor of glucose to all corneal layers?

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

    Which layers of the cornea is highly lipophilic?

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

    What is the principal provider of energy to epithelial cells?

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

    Corneal epithelial cells have the ability to alter corneal thickness by moving which ion into the tears?

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

    What does glucose convert to by glycolysis?

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

    What can lactic acid not pass through?

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

    What is the effect of corneal stress on lactic acid accumulation?

    <p>Mild corneal edema</p> Signup and view all the answers

    What happens to oxygen levels during sleep?

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

    What drives the movement of K+ and Cl- into the corneal epithelium?

    <p>Na/K pump and Na+K+Cl- cotransporter</p> Signup and view all the answers

    What is the primary driving force for water movement out of the corneal endothelium?

    <p>Anions Cl- and HCO3-</p> Signup and view all the answers

    What happens to the partial pressure of O2 in the tears when the eye is closed?

    <p>Decreases to 55 mmHg</p> Signup and view all the answers

    Where does the cornea primarily receives oxygen from where?

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

    What cells contribute to corneal regeneration and are derived from limbal stem cells?

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

    What is the primary driving force for water movement between the corneal endothelium and anterior chamber?

    <p>Concentration gradient of ions</p> Signup and view all the answers

    What is the primary function of the K+ channel in response to corneal changes in pH?

    <p>Moving more K+ into the aqueous</p> Signup and view all the answers

    What is the primary factor contributing to the dehydration of the cornea?

    <p>Movement of K+ into the aqueous</p> Signup and view all the answers

    What is the first response of injury to epithelium?

    <p>Stop basal cell mitosis</p> Signup and view all the answers

    Which condition is characterized by small hyaline excrescences on the posterior surface of Descemet’s membrane at the periphery of the cornea?

    <p>Hassall-Henle bodies</p> Signup and view all the answers

    What corneal dystrophy is associated with the poor attachment between the epithelium and its basement membrane?

    <p>Recurrent corneal erosion</p> Signup and view all the answers

    What is the characteristic feature of keratoconus?

    <p>Degeneration of the stroma</p> Signup and view all the answers

    What is the primary cause of corneal edema resulting in impaired visual acuity?

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

    What is the characteristic feature of corneal guttata?

    <p>Presence of endothelial dysfunction</p> Signup and view all the answers

    Which layer of the cornea can replace itself if damaged, leading to scar formation?

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

    Which condition is characterized by the projection of the affected area outward in a cone shape due to the force exerted on weakened areas by intraocular pressure?

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

    The limbal stem cells of the cornea are found in the Palisades of Vogt.

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

    You are only able to see Descemet's membrane when there is corneal swelling.

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

    Herpes simplex virus is always bilateral.

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

    What is the approximate thickness of the thinnest area of the sclera where EOM rectal muscles insertion occurs?

    <p>0.3 mm</p> Signup and view all the answers

    Which type of collagen fibers makes up the majority of the composition of the scleral stroma?

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

    What is the primary function of the episclera in relation to the sclera?

    <p>It is a loose, vascularized connective tissue layer outer to the sclera.</p> Signup and view all the answers

    What is the primary contributor to the dehydration of the sclera?

    <p>Number of glycosaminoglycans (GAGs)</p> Signup and view all the answers

    Which condition is characterized by a potentially destructive inflammatory process involving the scleral collagen or vasculitis?

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

    What is the primary cause of scleral ectasia?

    <p>Axial elongation in high myopic eye</p> Signup and view all the answers

    What is the primary blood supply for nourishment of the sclera?

    <p>Anterior ciliary vessels</p> Signup and view all the answers

    What part of the sclera attaches to the Tenon's capsule?

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

    What is the primary cause of scleral thinning in scleritis?

    <p>Connective tissue disorders</p> Signup and view all the answers

    What is the primary innervation of the posterior sclera?

    <p>Short ciliary nerves</p> Signup and view all the answers

    What is the characteristic feature of scleral foraminas?

    <p>Bridged by a network of scleral tissue called Lamina cribosa</p> Signup and view all the answers

    What is the posterior scleral spur an origin for?

    <p>Long ciliary muscle fibers</p> Signup and view all the answers

    What is the primary component of the scleral stroma?

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

    What is the primary orientation pattern of the collagen bundles in the scleral stroma in relation to the extraocular muscle tendinous insertions?

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

    The stromal ground surface is similar to the cornea but has more fibroblasts and GAGs.

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

    Branches of the short ciliary nerves innervate the medial and anterior sclera.

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

    Medial and anterior sclera are innervated by long ciliary nerves.

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

    What disease is associated with the progression of myopia that thins the sclera?

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

    Which layer of the cornea can store O2?

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

    Study Notes

    Corneal Histological Features

    • The cornea is approximately 71mm in size and is the principal refracting component of the eye.
    • It is transparent and avascular, providing optimal light transmittance.
    • The corneal layers include the epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium.
    • The corneal epithelium is a stratified squamous nonkeratinized epithelium, approximately 50 μm thick and consists of surface, wing, and basal layers.
    • The basal layer contains stem cells responsible for corneal epithelial renewal, with a turnover time of approximately 7 days.
    • Bowman’s layer is an acellular dense layer composed of random collagen fibrils, approximately 8-14 μm thick and is prenatally produced.
    • 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 stroma form parallel layers called lamellae, contributing to corneal transparency.
    • Ground substance in the stroma contains proteoglycans and contributes to the relatively high stromal hydration.
    • Descemet’s membrane is the true basement membrane of the endothelium, constantly produced, and thickens throughout life.
    • It consists of two laminae, with the anterior lamina being 3μm thick and exhibiting a banded appearance.
    • Corneal nerves pass through Bowman’s layer, losing their Schwann cell covering, and the endothelium's Descemet’s membrane thickens throughout life.

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    Related Documents

    The Cornea PDF
    Corneal Physiology And Clinical Applications PDF
    Sclera PDF

    Description

    Test your knowledge of the corneal histological features with this quiz. Explore the layers, composition, and unique characteristics of the cornea, including the epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium. Ideal for students and professionals in ophthalmology and optometry.

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