Lecture 44 4/29/24 Flashcards by Danika Boltz

What are the characteristics of the eyelids?

-upper and lower eyelids
-above and below the palpebral fissures
-lateral and medial fissures
-haired skin on the outside

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What are the Meibomian glands?

sebaceous glands in the eyelids that contribute to the tear film

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What are the characteristics of the conjunctiva?

-skin transitions to conjunctiva at the eyelid margin
-conjunctiva transitions to corneal epithelium at the limbus
-bulbar and palpebral conjunctiva

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What is the limbus?

transition between the clear and white parts of the eye

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What are the characteristics of the conjunctival epithelium?

-stratified columnar to stratified squamous
-contains goblet cells
-goblet cells contribute to tear film

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What are the characteristics of the third eyelid?

-aka nictitating membrane
-cartilage core
-lined by palpebral conjunctiva on eyelid side
-lined by bulbar conjunctiva on globe side

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What are the characteristics of the lacrimal gland?

-associated with third eyelid
-mucous and serous components

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What are the characteristics of conjunctiva-associated lymphoid tissue?

-immune cells closely associated with the conjunctival epithelium
-diffuse unencapsulated
-involved in antigen detection

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What are the three tunics of the globe?

-fibrous tunic
-vascular tunic
-nervous tunic

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What are the characteristics of the fibrous tunic?

-forms the outside of the globe
-cornea forms the front
-sclera forms the back

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What is the corneal epithelium?

non-keratinizing stratified squamous epithelium

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What are the characteristics of the corneal stroma?

-contains keratocytes
-layers of collagen
-avascular
-highest concentration of nerves in the body

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What are the characteristics of the sclera?

-consists of connective tissue with nerves and blood vessels
-can contain cartilage or bone in birds and fish

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What are the characteristics of the pupil?

-empty space bordered by the iris
-changes shape and size

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What are the characteristics of the uvea?

-part of the vascular tunic
-comprised of anterior uvea and posterior uvea

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What are the components of the anterior uvea?

-iris
-ciliary body

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What is the main component of the posterior uvea?

choroid

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What are the characteristics of the iris?

-colored part
-muscles contract and relax to change pupil size/shape

Which structures can be found within the iris?

-fibroblasts
-collagen
-melanocytes
-blood vessels
-lymphatics
-nerves
-muscles
-epithelium (posterior)

Which muscles are present within the iris?

-sphincter muscle (closer to pupil)
-dilator muscle

What are the characteristics of the ciliary processes?

-two layers of epithelium
–pigmented deeper layer and unpigmented upper layer
–continuous with epithelium on posterior surface of iris
-makes the aqueous humor

What is aqueous humor?

ultrafiltrate of the blood used to nourish the eye

What are the characteristics of the zonule fibers?

-arise from ciliary body and attach to margins of lens
-contraction of ciliary body muscles adjusts shape for lens for focusing

What are the characteristics of the lens?

-held in place by zonule fibers
-avascular
-nourished by aqueous humor

What are the layers surrounding the lens?

-lens capsule (outer) -lens epithelial cells (inner; anterior side only)

What is the lens bow?

lens epithelial cells migrate inwards and lose organelles as they continue to proliferate

Why does the lens get denser with age?

lens fibers are continually made and laid down on top of each other

What are the characteristics of the posterior lens?

-no lens epithelial cells -thin lens capsule

What is a cataract?

-any opacity in the lens -disruption of normal lens fiber arrangement

What are the characteristics of the anterior chamber?

-space behind cornea and in front of iris leaflets -contains aqueous humor

What are the characteristics of the posterior chamber?

-space behind iris leaflets and in front of the front half of the lens -contains aqueous humor

What is the iridocorneal angle?

where aqueous humor flows out of the eye

What is the pectinate ligament?

anterior margin of the iridocorneal angle

What is the path of aqueous humor through the iridocorneal angle and beyond?

-iridocorneal angle -trabecular meshwork -angular aqueous plexus -scleral plexus

What is the normal eye pressure?

aqueous humor produced by ciliary body - aqueous humor lost through outflow

What is glaucoma?

obstruction to aqueous humor outflow

What are the characteristics of the vitreous chamber?

-aka "posterior compartment" -filled with gelatinous, transparent vitreous humor -vitreous humor helps hold lens and retina in place

What are the characteristics of the retina?

-nervous tunic -composed of photosensitive retina, pigmented retinal epithelium, and non-pigmented retinal epithelium

What is the function of photoreceptors?

sense the light coming into the eye

What are the characteristics of the retinal pigmented epithelium?

-cuboidal -eats and interacts with photoreceptor outer segments -not always pigmented in animals

Where are retinal blood vessels found, if present?

-always within the inner retina -can be within or on top of the retina

What is the role of the choroid?

nourish the retina

What is the role of the tapetum lucidum?

reflects the light that has just passed through the retina to restimulate retinal photoreceptor cells and enhance night vision

How does the tapetum lucidum differ between carnivores and herbivores?

carnivores: tapetum cellulosum with brick-shaped cells herbivores: tapetum fibrosum with regularly arranged collagen