Anatomy - Globe Flashcards
External fibrous tunic
Contains the cornea and sclera
Middle vascular tunic
Contains the urea
Iris, ciliary body, choroid
Internal nervous tunic
Contains retina (3 parts)
Chambers of the eye
Anterior chamber - anterior to iris, aqueous humor
Posterior chamber - between iris and ciliary body/zonules, aqueous humor
Vitreous chamber - vitreous body - larges acellular, a vascular, gelatinous
Lens
Tunics surrounding globe
Fibrous - completely surrounds globe
Vascular and nervous - incomplete
Sclera
Forms 75-80% of the posterior globe
Comprised of dense feltwrok collagenous & elastic fibers
Toughness resists pressure of inner aqueous or gelatinous bodies & gives shape to globe
Features of sclera
Opaque
Relatively few vessels
Fibers of optic nerve exits area cribrosa near caudal pole
Cornea
Forms anterior 20-25% of globe
Projects (bulges) anteriorly from sclera
Normally clear and colorless
Features of cornea
Distinctly demarcated from sclera at the corneoscleral junction or limbus
Locating inflammation - if vessels move when you touch them, located to conjunctiva if dont move its in sclera
Uveitis
Inflammation of the uvea or middle tunic
Common in Appaloosa horses
Cilliary body & processes
Body - near limbus,
Processes - bears a 360 series of elevations of processes
Zonular fibers - suspensory ligaments of lens, extend from cilliary processes to the lense & suspending it and provide function
Iris
Variably color extension of choroid
Suspended from edge of ciliary body and sclera
Pupil is the central opening, diameter can change
Pupil differently shaped among domestic animals
Corpora Nigra or iridic granules
Found in ungulates. Extensions of Iris found in horses
Horizontal pupils
Allow for better vision /field of view of the ground/surrounding areas
Can help eliminate dazzling light or refraction
Iris - smooth muscles
Innervated by CN and control pupil size
Dilator - radial fibers throughout iridial substance
- mydriasis (dilation)
Sphincter - circumferential fibers surrounding pupillary margin
- under PNS control
- myosis (constriction)
dilator
Dilator - radial fibers throughout iridial substance
- mydriasis (dilation)
Sphincter
Sphincter - circumferential fibers surrounding pupillary margin
- under PNS control
- myosis (constriction)
Cats & pupils
Small cats have vertical pupils when constricted, round when dilated
Big cats have round pupils
Parts of vascular tunic
Choroid - lines posterior & circumferential parts of globe
Black pigmented inside
Tapetum lucidum
Unpigmented part of of choroid in all domestic mammals except pigs
- lies dorsal to fundus
- reflects photons bc of absence of pigment
- gives eye shine at night among species
fundus
Internal portion of globe visible via scope
Ora serrata
Ridge or edge at the junction of visual and non-visual retina caused by the sudden thinning of tissue as rods and cones are lost. Also demarcates choroid from ciliary body
Lens
Flexible, layered structure that changes shape to focus light onto retina
Generally is asymmetrically biconvex anterior curvature is less than posterior
Constantly under tension, zonular fibers attach here
Action fo ciliary muscle & body alter lens shape by altering tension on capsule
Chamber behind lens
Vitreous chamber
Anterior and posterior chamber
Aqueous humor produced by ciliary epithelium (pars ciliaris retinae) moves from posterior chamber to anterior chamber & is returned to venous circulation via spaces of Fontana at iridocorneal angle
Cause for glaucoma
Blocked iridocorneal angel and spaces of fontana
Nervous tunic
Pars optica retinae
Pars ceca retinae (posterior epi on iris and ciliary body)
Direct outgrowth of developing brain
innervation of eye
CNII - visual afferent
CNIII - pregang PNS fibers - ciliary ganglion in orbit
CNV - ophthalmic branch GSA fibers
Innervation of Extraocular structures
CNIII - orbital fissure
CNIV - orbital fissure
CNV - trigeminal
ophthalmic branch via orbital fissure - afferent from eyelids & conjunctiva (medial)
Maxillary branch via round foramen - afferent from eyelids & conjuctiva (Lat/vent)
