Anatomy of the Eye: Tarsal Plates, Conjunctiva, Iris

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Questions and Answers

What is the primary function of the tarsal plates?

Support eyelid shape and protect the eye (correct)

Connect the eyelid to the surrounding tissues

Facilitate tear production

Contain stem cells for conjunctival regeneration

What is the epithelial layer of the palpebral conjunctiva primarily composed of?

Simple squamous epithelium

Transitional epithelium

Stratified columnar epithelium (correct)

Cuboidal epithelium

Which feature distinguishes the epithelial layer of the upper lid from that of the lower lid?

The upper lid epithelium is continuous with the skin epithelium

The upper lid epithelium contains more goblet cells

The thickness of the epithelial layer varies, being 2-3 cells thick in the upper lid and 3-4 cells thick in the lower lid (correct)

The lower lid epithelium is primarily composed of basal cells

At what location do stem cells that repopulate the palpebral conjunctival epithelium reside?

At the mucocutaneous junction of the lid margin Signup and view all the answers

How does the epithelium of the bulbar conjunctiva change near the limbus?

It becomes stratified squamous Signup and view all the answers

What is the function of the bundles of collagen fibrils surrounding the iris vessels?

They protect the vessels from kinking and compression. Signup and view all the answers

Which structure is responsible for the constriction of the pupil during miosis?

Sphincter muscle Signup and view all the answers

Where is the minor circle of the iris located?

In the iris stroma at the collarette Signup and view all the answers

Which characteristic is true about the iris capillaries?

They are involved in the formation of the blood-aqueous barrier. Signup and view all the answers

What is the innervation responsible for the function of the sphincter muscle?

Parasympathetic nervous system Signup and view all the answers

What is the main function of the dilator muscle in the iris?

To pull the pupillary portion toward the root and enlarge the pupil Signup and view all the answers

Which type of epithelium composes the apical portion of the iris?

Cuboidal epithelium Signup and view all the answers

What changes occur to the posterior iris epithelium as it extends into the ciliary body?

It loses its pigment Signup and view all the answers

How are the anterior and posterior iris epithelial layers positioned?

Apex to apex Signup and view all the answers

What type of muscle processes are found in the basal portion of the iris?

Smooth muscle Signup and view all the answers

What anatomical feature encircles the pupil and displays a serrated appearance?

The pupillary ruff Signup and view all the answers

What is the structural characteristic of the posterior iris epithelium?

Single layer of heavily pigmented columnar cells Signup and view all the answers

What type of junctions connect the epithelial cells within the iris?

Tight junctions and desmosomes Signup and view all the answers

What is the role of the non-pigmented ciliary epithelium?

Creating a barrier between blood and aqueous humor Signup and view all the answers

What type of cell junctions are predominantly found near the apices of the ciliary epithelial cells?

Gap junctions Signup and view all the answers

How do the retinal pigment epithelial (RPE) cells differ in structure between the posterior pole and the ora serrata?

Hexagonal at posterior pole, cuboidal at ora serrata Signup and view all the answers

Where does the non-pigmented ciliary epithelium transition into pigmented iris epithelium?

At the ora serrata Signup and view all the answers

Which layer is NOT part of the retina's ten layers?

Choriocapillaris layer Signup and view all the answers

What is the attachment site for zonular fibers associated with the ciliary body?

The internal limiting membrane Signup and view all the answers

What primarily constitutes the retinal pigment epithelial (RPE) layer?

Pigmented hexagonal cells with melanosomes Signup and view all the answers

Which of the following structures is involved in the metabolic activity and secretion of aqueous humor components?

Non-pigmented ciliary epithelium Signup and view all the answers

What is the range of crystallin concentration in the lens from the cortex to the nucleus?

15% in the cortex to 70% in the nucleus Signup and view all the answers

What is the primary function of the anterior lens epithelium?

Capsule secretion and metabolic transport Signup and view all the answers

Which part of the lens is primarily involved in cell division and differentiation?

Germinal zone near the equator Signup and view all the answers

How does the lens handle UV radiation wavelengths greater than 400 nm?

Transmits to the retina Signup and view all the answers

What part of the lens first encounters UV radiation?

Lens epithelium Signup and view all the answers

What structural feature contributes to the concentric layers of the lens?

Desmosomes and complex interdigitating junctions Signup and view all the answers

What is the width of the ciliary body on the temporal side?

6.7 mm Signup and view all the answers

What is the consequence of unstable free radicals produced by UV exposure on the lens?

Morphological changes leading to irreversible damage Signup and view all the answers

Study Notes

Tarsal Plates

Composed of dense connective tissue
Collagen fibrils of the tissue are uniform in size and run vertically and horizontally
Contain Meibomian glands for tear production
Support eyelid shape, eye protection and facilitate eye movement

Conjunctiva

Composed of two layers: stratified epithelium and connective tissue stroma
Epithelium continuous with skin epithelium at the mucocutaneous junction of the lid margin
Epithelium is 2-3 cells thick in the upper eyelid and 3-4 cells thick in the lower eyelid
Epithelium changes to stratified squamous near the limbus
Connective tissue layer provides support

Iris

Iris arteries originate from the major circle of the iris located in the ciliary body near the iris root
Iris vessels follow a radial course from the iris root to the pupil margin
Iris capillaries are not fenestrated and form part of the blood-aqueous barrier
Iris stroma is continuous with the stroma of the ciliary body
Sphincter muscle is a circular muscle located in the pupillary zone of the stroma
Sphincter muscle contraction constricts the pupil (miosis) and is innervated by the parasympathetic system

Anterior Epithelium and Dilator Muscle

Anterior iris epithelium is composed of myoepithelial cells
Apical portion is pigmented cuboidal epithelium
Basal portion contains elongated, contractile, smooth muscle processes
Dilator muscle extends from the iris root to below the midpoint of the sphincter
Dilator muscle fibers are arranged radially and contraction enlarges the pupil (mydriasis)
Dilator muscle is sympathetically innervated

Posterior Epithelium

Posterior iris epithelium is a single layer of heavily pigmented, columnar cells
Posterior iris epithelium loses pigment as it continues into the ciliary body as the nonpigmented epithelium
Posterior iris epithelium is continuous with the pigmented epithelium of the ciliary body at the pupillary margin, forming the pigmented pupillary ruff

Lens

Lens capsule is a thin, acellular membrane surrounding the lens
Lens contains crystallins which contribute to the refractive index gradient
Crystallin concentration is higher in the nucleus than in the cortex
Anterior lens epithelium is involved in capsule secretion and metabolic transport
Germinal zone near the equator is where cell division occurs and new lens fibers are created
Lens fibers elongate and differentiate, forming concentric layers of the lens

Ultraviolet Radiation

The cornea absorbs wavelengths below 300 nm
The lens absorbs wavelengths between 300 and 400 nm
The retina receives wavelengths greater than 400 nm
Lens absorbs almost all UV light and unstable free radicals cause molecular changes
Lens epithelium is susceptible to damage from free radicals

Ciliary Body

Ciliary body is a ring-shaped structure
Non-pigmented ciliary epithelium is continuous with the posterior iris epithelium
Lateral walls of non-pigmented epithelial cells are joined by desmosomes, gap junctions and zonula occludens: these form part of the blood-aqueous barrier
Non-pigmented epithelial cells are involved in secretion of aqueous humor and act as a diffusion barrier between blood and aqueous humor

Retina

Retinal pigment epithelium (RPE) is the outermost retinal layer and is a single cell layer
RPE cells contain melanin granules that extend from the apical to the middle portion of the cell
RPE cells become larger and more cuboidal as the layer nears the ora serrata
RPE cells are involved in light absorption and the visual cycle

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Description

Explore the intricate structures of the eye, including the tarsal plates, conjunctiva, and iris. This quiz covers the composition, functions, and significance of each component in eye anatomy. Test your knowledge and understanding of these essential features.