Podcast
Questions and Answers
What is the primary function of the tarsal plates?
What is the epithelial layer of the palpebral conjunctiva primarily composed of?
Which feature distinguishes the epithelial layer of the upper lid from that of the lower lid?
At what location do stem cells that repopulate the palpebral conjunctival epithelium reside?
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How does the epithelium of the bulbar conjunctiva change near the limbus?
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What is the function of the bundles of collagen fibrils surrounding the iris vessels?
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Which structure is responsible for the constriction of the pupil during miosis?
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Where is the minor circle of the iris located?
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Which characteristic is true about the iris capillaries?
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What is the innervation responsible for the function of the sphincter muscle?
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What is the main function of the dilator muscle in the iris?
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Which type of epithelium composes the apical portion of the iris?
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What changes occur to the posterior iris epithelium as it extends into the ciliary body?
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How are the anterior and posterior iris epithelial layers positioned?
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What type of muscle processes are found in the basal portion of the iris?
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What anatomical feature encircles the pupil and displays a serrated appearance?
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What is the structural characteristic of the posterior iris epithelium?
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What type of junctions connect the epithelial cells within the iris?
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What is the role of the non-pigmented ciliary epithelium?
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What type of cell junctions are predominantly found near the apices of the ciliary epithelial cells?
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How do the retinal pigment epithelial (RPE) cells differ in structure between the posterior pole and the ora serrata?
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Where does the non-pigmented ciliary epithelium transition into pigmented iris epithelium?
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Which layer is NOT part of the retina's ten layers?
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What is the attachment site for zonular fibers associated with the ciliary body?
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What primarily constitutes the retinal pigment epithelial (RPE) layer?
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Which of the following structures is involved in the metabolic activity and secretion of aqueous humor components?
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What is the range of crystallin concentration in the lens from the cortex to the nucleus?
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What is the primary function of the anterior lens epithelium?
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Which part of the lens is primarily involved in cell division and differentiation?
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How does the lens handle UV radiation wavelengths greater than 400 nm?
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What part of the lens first encounters UV radiation?
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What structural feature contributes to the concentric layers of the lens?
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What is the width of the ciliary body on the temporal side?
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What is the consequence of unstable free radicals produced by UV exposure on the lens?
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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.