Test 2: lecture 23: eye Flashcards
where eyelids meet
canthus (medial and lateral)
sebaceous glands in the eyelid
meibomain gland
punctae
opening of the meibomain gland in the eye lid
the opening between the eyelids
palpebral fissure
the eyelid/conjunctiva is composed of two parts
bulbar conjunctiva covers the globe
palpebral conjunctiva lines the inner aspect of the eyelid
the two parts meet at the fornix
two muscles of the eyelid
levator palpebrae superioris elevated the upper eyelid and keeps the eyelid open, voluntary
oribularis oculi- closes the eyelids
the conjunctiva is ___ epithelium and contains large and actively secretory goblet cells that produce mucin component of the pre-corneal tear film
stratified columnar
3rd eyelid
ocular adnexae (nictitating membrane)
The vertical bar of the T of the third eyelid is surrounded by the superficial gland of the third eyelid at its base which is a ____ gland that produces an aqueous secretion
tubulo-alveolar
tear fluid is made by
superficial gland of the third eyelid
lacrimal gland located superotemporal to the globe
KCS
insufficient tear (keratoconjunctivitis sicca)
epiphora
overflow of tears secondary to obstruction of the lacrimal duct
lacrimation
irritation or inflammation
The ___ keeps the cornea moist
pre corneal tear film (PCTF)
Tears are drained away from the eye via ___
the nasolacrimal drainage system
lacrimal puncta → canaliculus → lacrimal sac → nasolacrimal duct
pre corneal tear film is made by
superficial: oily (meibomain gland)
middle: aqueous (lacrimal and 3rd eyelid)
inner: mucoid (goblet cells)
Three tunics of the eye
outer (fibrous)
middle (vascular)
inner (sensory)
the outer fibrous chamber of the eye:
cornea- transparent
sclera
the middle vascular tunic of the eye
uveal tract
anterior- ciliary body and iris
posterior- choroid
The inner sensory tunic of the eye
retina
two ocular chambers
anterior and posterior
space between the anterior face of the iris and the posterior surface of the cornea
anterior chamber
space between the posterior surface of the iris (anteriorly) and the anterior face of the vitreous (posteriorly)/anterior surface of lens except in pupil area.
posterior chamber
The junction between the clear anterior part of the fibrous tunic (the cornea) and the opaque caudal part of the fibrous tunic (the sclera) is called the___
limbus.
The ___ comprises the bulk of the fibrous tunic. In contrast to the cornea, it consists of irregularly arranged collagen fibrils of variable size
sclera
Posteriorly, the sclera is sieve-like in a discrete region, called the area (lamina) ____. The openings in the scleral tunic at this point allow the optic nerve axons (the axons of the ganglion cell layer of the retina) to exit.
cribrosa
cornea has ___ epithelium
non-keratinized stratified squamous epithelium
what makes the cornea transparent?
avascular
- non-keratinized stratified squamous epithelium
- no pigmentation
- collagen fibrils: uniform size and highly ordered embedded in a proteoglycan matrix. Fibrils are produced by stromal cells called keratocytes.
- dehydrated stroma 2ry to corneal endothelial function.
the “wettability” of the pre-corneal tear film depends on the mucin layer of the PCT that is secreted by ___ cells. It reduces the surface tension of the tear film and distributes it over the corneal surface.
goblet
cornea
___ keeps the cornea dehydrated and allows spacing of collagen fibrils to remain uniform
sodium/potassium ATPase pump
corneal epithelial are attached to the basement membrane by ___ and attached to each other by ___
laminin
E-cadherin
corneal epithelial cells come form ___ where epithelial stem cells generate transient amplifying cells that then migrate over the basement membrane and form basal corneal epithelial cells
limbus
the choroid, ciliary body and iris make up the ___
middle tunic of the eye- the uvea
the ___ part of the eye is highly vascular, often heavily pigmented and rich in elastic tissue
uvea
the iris is highly vascular, heavily pigmented and composed of ___arranged connective tissue fibers
loosely
corpora iridica
The amount of ___ pigment present in the iris determines what color the eyes are perceived to be (blue eyes have less pigment and brown eyes have more)
melanin
Blue eyes have no pigment in ___, but pigment in the ___
iris stroma
iris epithelium
Brown eyes (top right) have pigment in both the ___ and ___
stroma
iris epithelium
Albino eyes lack pigment in iris and other parts of the eye as well, and appear red because the ___ blood vessels are visible.
iridal
non-visual retina =
(pars iridica retinae).
The iris is covered on its posterior surface by an epithelium (the posterior iris epithelium), which – like the ciliary epithelium – is considered to be part of the non-visual retina (pars ____).
iridica retinae
The ____will decrease the size of the pupillary opening when it contracts (miosis) and is innervated by axons of the parasympathetic division of the ANS.
sphincter muscle
The ___ muscle will increase the size of the pupillary opening when it contracts (mydriasis) and is innervated by the sympathetic division of the ANS.
dilator
ciliary body and processes make fluid which go ___
from the posterior chamber to the anterior chamber and out of the irido-corneal angle
___ body make a secretion. The active secretion is based on the enzyme carbonic anhydrase.
Ciliary
Carbonic anhydrase inhibitors are used clinically to reduce intraocular pressure when it is elevated (___)
glaucoma
Note that the ciliary epithelium consists of a double layer; the internal layer (close to the vitreous) is ___ while the deeper (external) layer is ___
not pigmented
pigmented
the lens is transparent. Together with the ___, focuses light on the retina
cornea
The lens is a___structure that, along with the cornea and vitreous body, has the anatomical property of transparenc
biconvex
suspensory apparatus of lens
zonular ligaments arise near base of ciliary body and course along the ciliary processes to insert at lens equator. These are easily seen in the fixed eye after opening. In histologic sections, the fine zonular ligaments are difficult to see.
___ hold the lens in place
zonular ligaments
Contraction of ciliary muscle (circumferential) acts to decrease the ___ diameter of eye in the plane of ciliary processes/lens. This releases tension on the lens which, having inherent elasticity, increases it’s anterior-posterior dimensions. This process is termed “accommodation” and is used in near vision. Most developed in primates.
horizontal
The ___consists of an enveloping basement membrane (the lens capsule) made up of Type IV collagen, an anterior epithelium and a stroma made up of lens fibers without nuclei (nuclei are lost as the lens fibers differentiate
lens
Where cell division and fiber elongation occur in the lens
only at equator (lens bow region)
The shape of the lens is determined by the ___capsule, and the tension on the lens by the ciliary body (i.e. ciliary muscle) acting through the zonular ligaments.
elastic lens
In postnatal life, the lens epithelium is present only on the ___ surface of the lens.
anterior
The posterior lens epithelium, present in the embryo/fetus, was converted to lens fibers (primary lens fibers) during early prenatal lens development. The primary lens fibers are surrounded by the secondary lens fibers, and form the ___of the lens. The secondary lens fibers are the cortex of the lens
“nucleus”
The ___of the eye is that region of the inner posterior portion of the globe that can be viewed using an ophthalmoscope
fundus
The ___includes the optic disc, retinal and choroidal vasculature, tapetum lucidum and adjacent nontapetal region.
fundus
When viewed during a funduscopic (ophthalmoscopic) examination, the ___ (cellular in dogs and cats, fibrous in horse, cow, sheep) appears triangular in outline with the base of the triangle located in the region of the optic disc.
tapetum lucidum
The position of the optic disc in relation to the tapetum can be variable (optic disc does NOT vary in position; the extent of coverage of the tapetum can vary).
In dogs and cats, the tapetal layer is ___(tapetum cellulosum). In horse, cow and sheep, the tapetum consists of ____(tapetum fibrosum). There are no clinical differences observed between the two forms of tapeta.
cellular
connective tissue
retinal ___ are larger in size but fewer in number
venules
retinal arterioles are ___ than venules
small and more numberous
the ___ is the yellow green structure behind the retina and located between the RPE and choroid
tapetum
___ have a fibrous tapetum, while ___ have a cellular tapetum
Herbivores
carnivores
zonular ligaments come off the ___ and attach to the lens
ciliary body
what side of the lens is thicker
anterior, where the cells are. cells produce type 4 collagen
optic disc is also called
blind spot
___ in the eye is semitransparent and has a tapetal zone and a non tapetal zone
retinal
tapetum nigrum
the pigment in the RPE and choroid in inferior quadrant [known as the non-tapetal region
The ____ is the most posterior of the three parts of the uvea
choroid
choroid is highly vascular and lies between the ____ and the sclera.
RPE/retina
An important function of the choroid is to provide nourishment to the ___ layers of the retina which has the highest degree of metabolic activity of any tissue.
outer
The tapetal layer is a choroidal modification located between the large ___ vessels externally, and the ___ internally
choroidal
retinal pigment epithelium/choriocapillaris
“Stars of Winslow ”
The openings in the tapetum through which choroidal arterioles pass through are visible with an ophthalmoscope
retina has___ layers
10
Retinal pigmented epithelium (RPE)
Photosensitive (photoreceptor) layer (rods and cones)
External limiting membrane- ELM
External (outer) nuclear layer- ONL
External (outer) plexiform layer- OPL
Internal (inner) nuclear layer- INL
Internal (inner) plexiform layer-IPL
Ganglion cell layer-GCL
Nerve fiber layer-NFL
Internal limiting membrane-ILM
at the periphery the RPE will ____
collapse into 1 cell layer of pigmented cells and the other 9 layers will collapse into a layer of non pigmented cells
where retina terminates is called the
ora serrata
zone lies between the anterior margin of the retina and the ciliary bodies.
