Lecture 44 4/29/24 Flashcards
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
What are the Meibomian glands?
sebaceous glands in the eyelids that contribute to the tear film
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
What is the limbus?
transition between the clear and white parts of the eye
What are the characteristics of the conjunctival epithelium?
-stratified columnar to stratified squamous
-contains goblet cells
-goblet cells contribute to tear film
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
What are the characteristics of the lacrimal gland?
-associated with third eyelid
-mucous and serous components
What are the characteristics of conjunctiva-associated lymphoid tissue?
-immune cells closely associated with the conjunctival epithelium
-diffuse unencapsulated
-involved in antigen detection
What are the three tunics of the globe?
-fibrous tunic
-vascular tunic
-nervous tunic
What are the characteristics of the fibrous tunic?
-forms the outside of the globe
-cornea forms the front
-sclera forms the back
What is the corneal epithelium?
non-keratinizing stratified squamous epithelium
What are the characteristics of the corneal stroma?
-contains keratocytes
-layers of collagen
-avascular
-highest concentration of nerves in the body
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
What are the characteristics of the pupil?
-empty space bordered by the iris
-changes shape and size
What are the characteristics of the uvea?
-part of the vascular tunic
-comprised of anterior uvea and posterior uvea
What are the components of the anterior uvea?
-iris
-ciliary body
What is the main component of the posterior uvea?
choroid
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
