Eye Flashcards
Describe the ectoderm.
-lens
-outer epithelium of cornea
-epithelium of palpebrae (eyelid)
Describe the mesoderm.
-corneal stroma
-sclera
-extraocular m
-ciliary m
-tunica vasculosa
Describe neuroectoderm.
-of diencephalon = forms optic cup that is connected by the optic stalk
-optic cup (2 layers) = retina + pigment epithelium
-optic stalk -> optic nerve
Describe the eyeball.
located in the orbit (bony socket of skull)
-lens
-3 layers
>outer fibrous tunic
>middle vascular (uveal) tunic
>inner retinal (neuroepithelial) tunic
Describe the adnexa.
accessory ocular structures
-palpebrae (eyelid)
-3rd eyelid & conjuctiva
-lacrimal apparatus
Describe the 3 tunics of the eye.
- Fibrous
-sclera
-cornea
-limbus - Vascular
-iridocorneal angle
-iris
-ciliary body
-choroid - Neuroepithelial (retinal)
-pigmented
-neural layer
Describe sclera.
- Sclera
-posterior portion of eye
-white opaque layer
>dense irregular CT
FUNCTIONS:
-protection
-shape
-insertion point for tendon of extraocular muscle
Describe Cornea.
-anterior portion
-avascular
-transparent
-supplied by sensory nerves (CN V)
-regen
-5 layers
Describe the 5 layers of the cornea.
- ae= anterior epithelium
- Anterior limiting lamina/subepithelial BM (supports lining epithelium)
- sp= substantia propria - corneal stroma (type 1 collagen)
- pl= posterior limiting membrane
= Descemet’s membrane (supports endothelium) - pe= posterior epithelium = corneal
endothelium
Rat cornea picture.
What are the factors contributing to corneal transparency?
- Avascular
- Collagen
- Proteoglycans between collagen
- Na/K ATPase & carbonic anhydrase = pumps water out (located in anterior & posterior corneal epithelium)
Clinical relevance of cornea.
Corneal ulcers destroy the epithelium, stroma, & descemets membrane.
Describe Limbus.
-corneosclera junction
-where the sclera overlaps the cornea
-nutrition for cornea = micro vasculature of limbus & aqueous humor
Describe the corneoscleral junction (CSJ) of the limbus.
-(S) = limbus
-epithelium of limbus is continuous with the conjunctiva (C) that lines the eyelids
-(I) = iris
-(AC) = anterior chamber
-(PC) = posterior chamber
Vascular Tunic (picture).
Describe the iris.
- Stroma
-pigmented
-loose CT
-iridial melanin = determines eye color - Dilatory & sphincter pupillae m
- Posterior epithelium
-iridic granules (corpora nigra) = in equine & ruminants at pupillary margins - Iridcorneal angle (filtration/drainage)
Iris (picture).
AC = anterior chamber
PC = posterior chamber
CP = constrictor pupillae
Describe albinism.
-melanocytes present but no genes for tyrosinase
-red color of eyes due to RBCs
-lack of melanin pigment
Describe iridocorneal angle.
-convergence of corneoscleral junction (limbus), ciliary body, & iris
-composed of:
>pectinate lig
>trabecular network
>trabecular (aqueous) veins
-draining point for aqueous humor
Describe the ciliary body.
-anterior expansion of choroid at level of the lens
-mechanical & secretory
-ciliary muscle
>sm muscle
>contracts during accommodation, reduces tension of zonal at fibers of lens
>loose CT (elastic fibers, vessels, melanocytes)
>CN III
Describe the ciliary processes.
-base of iris
-epithelial surface
>2 layers of columnar
>nonpigmented - ion transport forming aqueous humor
>pigmented - BM extends to form zonular fibers that suspend the lens
Ciliary process & body picture.
Closer picture of ciliary process.
Ciliary process picture.
Ciliary body picture.
SL = suspensory lig
ICA = iridocorneal angle
CB = ciliary body
What is the aqueous humor?
-anterior & posterior chamber
-nourish cornea & lens (glucose rich)
-maintain intraocular pressure
-formed by nonpigmented cells of ciliary process
-constant drain required at iridocorneal angle
What is the drainage pathway of aqueous humor?
Posterior -> pupil -> anterior -> iridocorneal angle -> pectinate lig -> scleral venous plexus
Describe the choroid.
-vascular
-nutrition for retina
-anterior = continuous w stroma of ciliary body
-external = connected to sclera
-internal = connected to retinal pigmented epithelium
-internal to vascular layer = tapetum lucidum
Choroid picture.
Choroid picture with tapetum lucidum.
Describe the 3 parts of the retina.
- Sensory/optical
-contacts choroid - Nonsensory/ciliary
-inner nonpigmented
-outer pigmented ciliary epithelium - Nonsensory/iridal
-posterior pigmented epithelium
What nourishes the retina?
-vessels of choroid
-retinal vessels entering via optic disk
Retina layer picture.
Retina & chorid picture.
Retina = nerve tissue & cells are ‘nerve cells’
Describe the sensory/optical retina layer.
-send visual image to brain
-10 layers
-held in place by vitreous body
-combined nerve fiber layer converge on optic disk to form optic nerve
Describe the general concept of optical retina. (3 neurons in succession)
- Light passes through layers of retina & stimulates photoreceptor cells (rods & cones).
- Impulse is passed to bipolar neurons & then to ganglion cells.
- Axons of ganglion cells form nerve fiber layer. These layers converge at optic disk (papilla) & leave eye as CN II.
Additional cells:
-amacrine = interneurons
-horizontal = regulate input from photoreceptors
-muller = glial cells
Describe the path of light & visual perception.
Path of light:
Tear film -> cornea -> aqueous humor -> pupil -> lens -> vitreous humor -> 8 layers of retina -> photoreceptors -> absorbed by retinal epithelium
Visual perception:
Visual impulse passes in reverse order from photoreceptor -> bipolar -> ganglion -> optic nerve -> brain
Describe the retinal pigmented epithelium.
-outermost layer
-flat, polygonal cells resting on BM
FUNCTIONS:
-transport nutrients & metabolites to photoreceptor cells
-light absorption
-phagocytosis
Describe the photoreceptor layer.
rods & cones have outer & inner segments connected through cilium
RODS:
-inner segment = long & thin
-flattened membranous disks
>pigment ‘rhodopsin’ (vit A) = vision in dim light
-120mil/retina
CONES:
-inner segment = broad base
-disks have ‘iodopsin’ = vision in bright light & color
-60mil/retina
Fovea picture.
Optic nerve picture.
What is a Fundic exam?
Clinical method to evaluate retina.
Describe the vitreous body.
-refractive media
-space between lens & retina (4/5th of eyeball)
-99% water
-rich in HCl Acid
-gel cortex & liquid center
-maintains shape & retinal apposition
-gelatinous, colorless, viscous fluid
Describe the lens.
-refractive media
-surrounded by capsule (thick on anterior)
-suspended by zonular fibers from ciliary processes
-lose vascular supply after development
1. anterior epithelium
>simple cuboidal
>apical towards lens
>@ equator = elongate & differentiate into lens fibers
2. lens fibers
>prism shaped
>lack nuclei
>interdigitate
>gap junctions (transparent)
>differentiation & growth of lens
Ciliary process picture with zonular fibers.
Lens capsule picture.
Lens fibers picture.
Differentiating & mature lens fibers picture.
lack nucleus & organelles when mature
Describe conjuctiva.
pseudostratified columnar or transitional epithelium that becomes stratified squamous near eyelid
[anemia detected by observation of mucous membrane = conjuctiva & 3rd eyelid]
Describe the eyelid (palpebra/blepharon).
-conjunctiva
-cilia (eyelash)
-tarsal (meibomian) glands - sebaceous
-3rd eyelid (nictitating membrane)
-lacrimal (tear) apparatus
>lacrimal glands
>lacrimal sac
>nasolacrimal duct
Conjuctiva picture.
Ce = conjunctival epithelium
G = goblet cells (palpebral conj)
Lp = lamina propria
Eyelid (palpebra) picture.
Describe the 3rd eyelid (nictitating membrane).
-protect eye by removing foreign material
-fold of conjuctiva formed by hyaline cartilage in ruminants & dogs & elastic cartilage in horse, pig, cat
-lined by conjunctiva
-aggregated lymphoid nodules located under conjunctival surface
-lacrimal gland = 30-50% of aqueous portion of tear film via multiple small ductules
Describe lacrimal glands.
-tear film
-moisturizes, lubricates, protects eye
-tubuloalveolar seromucinous acini (A) = secretory cells filled with small granules
-myoepithelial cells (M) at base
Describe the tear film layers.
- Oily
-produced by meibomian (tarsal) gland
-superficial layer - Aqueous
-sero-mucous produced by lacrimal gland - Mucous
-produced by goblet cells in conjuctiva
Describe pecten in birds.
-special adaptation
-cartilage in sclera & ossicles
-bird & reptiles = pectin
>vascular structure that extends from optic disc to vitreous body = nourish inner eye & retina
