Anatomy and Properties of the Cornea Quiz

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Questions and Answers

What are the five layers that make up the cornea?

Epithelium, Bowman’s layer, Stroma, Descemet’s membrane, Endothelium

Why is the cornea isolated from the blood supply?

To maintain transparency.

What is the role of the squamous stratified epithelium in the cornea?

It provides an optically smooth front surface to the cornea.

Which layer of the cornea is a passive barrier, stopping water from entering the stroma below?

Epithelium Signup and view all the answers

What provides strength, elasticity, and form to the cornea?

Corneal stroma Signup and view all the answers

Which layer of the cornea consists of narrow collagen fibrils and is around 12μm thick?

Bowman’s layer Signup and view all the answers

What are the three types of cells present in the epithelium of the cornea?

Basal, Wing, and Squamous Signup and view all the answers

What percentage of the total refractive power of the eye is contributed by the cornea?

65% Signup and view all the answers

What is ptosis, and which muscle is primarily involved in it?

Droopy upper eyelids, levator aponeurosis Signup and view all the answers

What are the three layers of the tear film, and what percentage of tears are produced by the accessory glands?

Lipid, aqueous, and mucous layers, 10% Signup and view all the answers

What is the structural form of a collagen molecule, and which type of muscle is Müller's muscle?

Trippel alpha helix, superior tarsal muscle Signup and view all the answers

What is the function of the plica semilunaris, and which part of the brain influences the lacrimal gland?

Vestigial 'third eyelid', hypothalamus Signup and view all the answers

What is the thickness of the sclera in the posterior region?

1mm Signup and view all the answers

What is the function of the limbus in relation to the cornea?

Nourishment of peripheral cornea Signup and view all the answers

What type of fibers are present in the sclera?

Collagen, proteoglycans, and elastic fibres Signup and view all the answers

What is the origin of the corneal nerves?

Ophthalmic division of trigeminal nerve Signup and view all the answers

What is the characteristic of the terminal axons in the cornea?

Very sensitive to pain and temperature Signup and view all the answers

Study Notes

Cornea Anatomy

The cornea has five layers: epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium.
The epithelium is the most anterior layer, 5-6 cells thick, and 50μm thick.
The epithelium is a stratified squamous epithelium, consisting of three types of cells: squamous, wing, and basal.
These cells undergo a 10-day cycle, with basal cells capable of division and repair.

Corneal Epithelium

The epithelium provides an optically smooth front surface to the cornea, along with the tear film.
Cells are bound together by desmosomes, and basal cells have gap junctions.
The epithelium is a passive barrier, stopping water from entering the stroma below.

Bowman's Layer

Bowman's layer is a modified portion of the stroma, with no cells and narrow collagen fibrils.
It is 12μm thick, and some species lack a Bowman's layer.

Corneal Stroma

The stroma provides strength, elasticity, and form to the cornea.
It is comprised of collagen, with a triple alpha-helix structure.
The stroma makes up most of the cornea.

Limbus

The limbus is the site of nourishment of the peripheral cornea.
It is involved in corneal wound healing and immunosurveillance.
It contains pathways of aqueous humor outflow and circumferential or tangential collagen fibrils.
It is the site of surgical incisions.

Sclera

The sclera is the outer coat of the eye, containing collagen, proteoglycans, and elastic fibers.
It is relatively avascular, with a thickness of 1mm (posterior) and 0.4mm behind muscle tendon insertions.
The sclera has variable fibril diameter.

Corneal Nerves

Corneal nerves are derived from the ophthalmic division of the trigeminal nerve.
Branches radiate to the anterior cornea from the limbus, and nerves lose their myelin sheaths in the cornea.
Terminal axons are very sensitive to pain and temperature.

Tear Film

The tear film has three layers: lipid, aqueous, and mucous.
The accessory glands produce 10% of tears.

Ptosis

Ptosis is the drooping of the upper eyelid.
The main muscle involved in ptosis is the levator aponeurosis.

Lacrimal Gland

The lacrimal gland is under the influence of the hypothalamus.
The lacrimal gland is innervated by sensory, parasympathetic, and sympathetic nerves.

Miscellaneous

The plica semilunaris is a vestigial "third eyelid".
The drainage system of tears is thought to be driven by pressure gradients.
Dr. Regini belongs to the Llandaff RC rowing club.

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Test your knowledge on the anatomy and properties of the cornea, focusing on its structure, dimensions, refraction capabilities, and more.