Lecture 21: Eye and Orbit I Flashcards
what is the vascular tunic
2nd/middle layer composed of the choroid, ciliary body, and iris
what is the fibrous tunic
scleral- outermost layer
cornea
what are the layers of the cornea in histology superficial to deep
epithelium- stratified squamous
Bowman’s membrane
collagen fibers
descement’s acellular
epithelium- squamous-columnar
what are the layers of the sclera in histology superficial to deep
conjunctival epithelium- stratified squamous
episclera
stroma- thick collagen
suprachoroid lamina with melanocytes
what muscle does the anterior layer of the iris contain and what does it do
constrictor pupillae, constricts the pupil
is the constrictor pupillae controlled by PNS or SNS
parasympathetics
what is the ciliary body
contains the ciliary muscle and changes lens shape for accommodation/focus
is the ciliary body controlled by PNS or SNS
parasympathetics
what layer of the eye contains blood vessels
choroid
what layer in eye can the retina be seen histologically
choroidal layer
what components make up the neural tunic
ora serrata, optic retina and posterior layer of the iris that contains the dilator pupillae muscle
what is the junction between the retina and ciliary body
ora serrata
what muscle lays in the posterior layer of the iris that dilates the pupil
dilator pupillae muscle
is the dilator pupillae muscle controlled by SNS or PNS
sympathetics
what is the canal of schlemn
drains approximately 2-3 microliters of aqueous humor per minute aqueous humor from the anterior chamber to the venous system
located on/in ciliary body
what is the prelental region of the eye and what fluid is filled there
anterior and posterior chambers, filled with aqueous humor
what is the retrolental region of the eye and what fluid is filled there
behind the lens, filled with vitreous fluid
what is the pathway of light
cornea–> aqueous humor–> iris—> lens–> vitreous humor–> retina
what structure makes up the majority of the neural tunic
retina
what structure contains photosensitive rods and cones
retina
what is the plexiform layer
synaptic connections between rods and cones to retinal ganglion neurons
what is the nuclear layer
contains neuronal cell bodies of rods and cones
what is the ganglion cell layer
axons leave the eye as the optic nerve
what photoreceptor cell type has vision in light of low intensity and is predominate throughout the retina
rods
what photoreceptor cell type has visual acuity and color vision
cones
what are the two types of cones are present
short and medium wavelength
what are the two color sensitivities in carnivores and artiodactyls
blue and green
feline vs human cones for color vision
humans- 3 cones at higher density and provides higher acuity
cats- 2 cones at much lower density provides higher sensitivity
feline vs human rods for color vision
humans- rods provide spatial detail but darker image
feline- rods at higher density provides higher sensitivity or brighter image
what is the tapetum lucidum
functions as reflector which directs photons back through retina. provides additional chance for photoreceptors to capture these photons
optic disk
location of exit for retinal ganglion cell axon
optic nerve
formed from bundles of axons from retinal ganglion cells, surrounded by meninges and CSF in the subarchanoid space
what is the result of increased intracranial pressure on the optic nerve
prevents normal blood flow through central retinal vessels
clinical sign: papilledema or choked disk
what keeps the lens capsule under tension
zonula fibers
where do zonula fibers attach
ciliary body
how does the lens change shape
change in tension of the suspensory ligaments
what structure is located rostral to the zonula fibers
iris
what kind of lens focuses on near objects
round lens
what kind of lens focuses on distant objects
flattened lens
constriction and relaxation of what muscle affects lens shape for changing focus
ciliary muscle
describe the role of the ciliary muscle, zonula fibers and lens shape to see distant objects
ciliary muscle is relaxed, zonula fibers under tension, and lens is flattened/stretched thin to see distant objects
describe the role of the ciliary muscles, zonula fibers and lens shape to see near objects
ciliary muscle is stimulated by parasympathetic innervation, causing muscle to contract, zonula fibers are relaxed, and in the absence of the tension from zonula fibers the lens becomes more circular to refract light for near objects
what bony components form the wall of the orbit
frontal, lacrimal, zygomatic and palatine
the lateral wall of the orbit is formed by what muscle
temporalis muscle
what is the postorbital ligament
forms later portion of the orbit
connects to frontal and zygomatic bones
tarsal (Meibomian) glands
modified sebaceous glands that secrete an oily substance that acts to increase the viscosity of tears and decreases tear evaporation from the surface of the eye
chalazion
inflammation/blockage of meibomian glands
what kind of tumor disrupts normal irrigation of the cornea
meibomian gland tumors
bulbar + palpebral conjunctiva=?
conjunctival sac- when eyes are closedw
palpebral conjunctiva
when eyes are open create superior and inferior fornices
what cell type is conjunctiva of eye
non-keratinized, stratified squamous epithelium with goblet cells
primary infectious conjunctivitis can be caused by
bacteria, viruses, mycoplasma, fungi and parasites
what structures anchor the eyelids and are the meeting points for upper and lower eyelids
lateral and medial palpebral canthi and commissures
nicitating membrane/third eyelid
deep to the upper and low eyelids, drawn across the cornea and sclera, thought to provide both protective and moistening functions
what muscle closes the eyelids
orbicularis oculi
what cranial nerve innervates orbicularis oculi
CN VII- facial
what muscle elevates the eyelids
levator palpebrae superiosis
what cranial nerve innervates levator palpebrae superiosis
CN III- oculomotor
lacrimal apparatus
controls tear production and drainage
what secretes tears
lacrimal gland
that lacrimal gland is under what kind of control
autonomic
what cell produces the glycoprotein component of tear film
goblet cells of the conjunctivae
tear summary: what gland produces tears, how do tarsal glands play a role and goblet cells
lacrimal glands secrete tears
tarsal glands secrete oily substance that increases viscosity of tears and decreases its evaporation and goblet cells secrete the glycoprotein component of tear film