Lecture 21 & 22: the eye Flashcards
define sclera
outermost cover of the eye
what is the episceral layer of the sclera
outer layer
loosely arranged collagen and elastic fibers
highly vascularized
attached the lining of the eyelid (conjunctiva) to sclera
what is the sclera proper
located in sclera
made of interlacing collagen fibers
attachment site for tendons of extrinsic eye muscles
define lamina cribosa
perforated disc of sclera
pass through the optic nerve fibers
define limbus
junction between sclera and cornea
what is the posterior of the sclera continuous with
dural covering of the optic nerve
define cornea
anterior continuation of sclera
what type of epithelium is in the cornea
stratified, nonkeratinized squamous epithelium
what is bowmans membrane
acellular layer that separates epithelium from stroma
what is the corneal stroma
thin layers of ordered arrays of collagen fibers
what is descements membrane
acellular, separates stroma from endothelium
what is included in the vascular tunic
choroid, ciliary body and iris
define choroid
extends anterior to ora serrata of retina
what forms the choriocapillar network and what is taht
choroid
contains small blood vessels that supply cell of retina
what is bruchs membrane
acellular fused basal laminae of choriocapillaris and pigmented retinal eptithelium
define ciliary body
wedge-shaped expansion of choroid peripheral to the lens and covered by double layer of cells
define iris
located anterior to the lens and separates the anterior and posterior chambers and surrounds pupil.
what epithelium is in the iris
inner layer: pigmented epithelial cells
outer layer: radially oriented myofilaments
what is the pigmented ring of the eye
iris
define the retina
photosensitive region that lies posterior to the ora serrata
define optic disc
region on posterior aspect of eye where optic nerve excises (no photosensitive retina and constitutes blind spot)
define fovea centralis
area in retina that contains only cone-type photoreceptors
what are the chambers of the eye
anterior: posterior to cornea and anterior to iris
posterior: posterior to iris and anterior to lens
vitreal: posterior to lens, contains vitreous body
where is the pigmented layer of the retina located
adjacent to choroid
what is the external limiting membrane of the retina
area at junction and outer segments of rods and cones and outer layer
includes adherens junctions between rods and cones and mueller cells
what is the outer layer of the retina
cell bodes of rods and cones (1st order neurons)
what is the outer plexiform layer of the retina
areas of synapses between axons of rods and cones and dendrites of bipolar neurons and horizontal cells
what is the inner nuclear layer of the retina
cell bodes of bipolar cells (2nd order neurons), horizontal cells, amacrine cells and mueller cells
what is the inner plexiform layer of the retina
area of synpases betweens axons of bipolar cells and dendrites of ganglion cells
what is the ganglion cell layer of the retina
cell bodies of ganglion cells (3rd order neurons)
what is the optic nerve layer of the retina
axons of ganglion cells
what is the internal limiting membrane of the retina
terminations of mueller cell processes and their basement membrane (support cells)
what are the cells of the retina
bipolar, horizontal, amacrine, mueller, ganglion
define bipolar cell
conducting nuerons that synapse with rods and cones
define horizontal cells
interneurons that interconnect rods and cones with each other and with bipolar cells
define amacrine cells of retina
interneurons that connect gangion cells and bipolar neurons
define mueller cells
neuroglialc cells that extend through the retina and form external limiting membrane via zonulae adherens between mueller cells and rods and cones
define ganglion cells
conducting neurons whose axons form the fibers of the optic nerve
define macula lutea
yellow region surrounding fovea, highest visual acuity
define fovea centralis
depressing of cone cells
define optic disc
lacks photoreceptors, point where ganglion cells turn into optic nerve (tract)
what do rods use as photopigment
rhodopsin
what do cones use as photopigment
iodopsins
what are the discs like in rods
discs attach from cell membrane and become free
constantly renewed
what are discs like in cones
discs remain attached to cell membran
what type of vision, lamellae, and sensitivity do rods have
black and white
not continuous lamellae
sensitive to low intensity lightg
what type of vision, sensitivity, and lamellae do cones have
color
high intensity sensitivity
continuous lamellae
define bleaching
disassembly of rhodopsin into opsin and retinal after light stimulation
define capsule of lens
insertion point for suspensory ligament
glycoproteins and type 4 collagen
secreted by subscapular epithelial cells
define the anterior epithelium of the lens
simple cuboidal epithelial
gives rise to cells that become lens fibers
define the lens nucleus
composed of lens cells that mature into fiber like stucture
devoid of nucleus and organelles
filled with crystalline proteins
what are the 2 types of glands in anterior surface of the eyelid
zeiss: sebaceous glands associated with eyelids
moll: sweat glands, ducts open into eyelash follicles
define palpebral fascia
fibrous core of eyelids
meobomian glands: secretion keeps normal tear film in eye
define palpebral conjunctiva
stratified columnar or squamous epithelium with goblet cells
lines inner surface of the eyelids
continuous with bulbar conjunctiva (covers eyeball)
what are the 3 tunics of the eye and what are the structures associated with each
fibrous: sclera, cornea
vascular: choroid, ciliary body, iris
inner: retina
