S2 Neuro Exam 5: Histology Of The Eye

Front 1

3 layers of the eye

Back 1

Fibrous layer (outer coat)
Vascular layer (middle coat)
Retinal layer (inner coat)

Front 2

Components of the Fibrous layer (outer coat)

Back 2

sclera-
dense opaque covering of posterior 5/6 eyeball
helps maintain shape of eye
contains scleral venous sinus/canal of Schlemm) near corneaoscleral jxn

-->corneaoscleral junction (limbus)

cornea-
transparent covering of anterior 1/6 eyeball

Front 3

Histology of the Sclera (fibrous layer)

Back 3

3 layers:
1. episclera= loose CT (vascular)
2. stroma= irregular thick collagen fiber bundles & fibroblasts
2. lamina fusca- suprachoroid lamina w/ melanocytes

Front 4

The sclera also contains lamina cribrosa, what are these specializations?

Back 4

areas where optic nerve fascicles & vessels penetrate the sclera
--> collagen fibrils arranged in circles/figure eights around openings for central retinal artery & vein
--> perforated disc appearance

Front 5

Histology of the Limbus (fibrous layer)

Back 5

loose conjunctival subepithelia CT w/ terminating conjunctival capillaries

contains internal scleral sulcus (w/ trabecular meshwork (spaces of fontana) & canal of Schlemm)- endothelium-lined channel= aqueous humor outflow= intraocular pressure control

contains scleral spur (origin of trabecullae)

Front 6

Components of the Cornea (fibrous layer)

Back 6

5 layers:
1. epithelium (avascular)
2. Bowman's membrane
3. Stroma (substantia propria)
4. Descernet's membrane
5. Endothelium

Front 7

Histology of Corneal Epithelium (fibrous layer)

Back 7

-stratified squamous nonkeratinized epithelium
-external surface w/ microvilli & microplicae (stabilize precorneal tear film)
-continuous w/ conjunctival epithelium (limbus)
-regenerative capacity (newest toward limbus)
-contains free nerve endings (touch, pain)

Front 8

Histology of Bowman's membrane (cornea, fibrous layer)

Back 8

-acellular, fine randomly arranged collagen fibrils
-helps anchor corneal epithelim
-protective barrier
-ends at limbus
(no regeneration= corneal scarring)

Front 9

Histology of Stroma (cornea, fibrous layer)

Back 9

-flattened, collagenous lamellae, parallel to corneal surface, oriented at right angles (regular arrangement)
-transparency influenced by diameter & spacing of collagen fibers
-flattened fibroblasts (keratocytes) btwn layers
-continuous w/ sclera & limbus

Front 10

Histology of Descernet's membrane (cornea, fibrous layer)

Back 10

- basement membrane for corneal endothelium
- extends into trabecular meshwork

Front 11

Histology of Corneal Endothelium (fibrous layer)

Back 11

-simple squamous epithelium
-maintains corneal hydration (stroma)
-allows passage of aqueous humor
-damage = swelling of stroma = loss of transparency

Front 12

Components of the Vascular layer (middle coat)

Back 12

3 parts:
Choroid
Ciliary body
Iris

Front 13

Components of Choroid (Vascular layer)

Back 13

*layer btwn sclera & retina (post 5/6 eyeball), firmly attached to pigmented retina, loosely attached to sclera, consists of choriocapillaris that supplies blood & nutrients to outer retina & supporting vessels

4 components:
Bruch's membrane
Choriocapillaris
Vascular layer
Suprachoroid

Front 14

Histology of Bruch's membrane (lamina vitrea) (choroid, vascular layer)

Back 14

- acellular membrane
- basal lamina for retinal pigment epithelium
- collagenous & elastic laters
- basement membrane for endothelium of choriocapillaris
- areas of thickening= Drusen

Front 15

Histology of Choriocapillaries (Choroid, Vascular layer)

Back 15

-bed of fenestrated capillaries
-greatest density near macula

Front 16

Histology of Vascular layer (Choroid, vascular layer)

Back 16

-intermediate & large feeder vessels for choriocapillaris

Front 17

Histology of Suprachoroid (Choroid, vascular layer)

Back 17

- thick transition layer btwn choroid & lamina fusca of sclera
- thin interconnected layers of melanocytes, fibroblasts, & CT fibers
- surrounding potential (suprachoroidal) space

Front 18

Components of Ciliary body (Vascular layer)

Back 18

*ring shaped structure surrounding lens, cont. w/ choroid behind & iris in front, connected to lens via zonular fibers of suspensory ligament, annular smooth muscle found w/i external portion
Fxn- suspend lens & control thickness

3 Components:
ciliary epithelium
ciliary body stroma
ciliary muscle

Front 19

The _____________ of the ciliary body are internal folds that produce aqueous humor (nourishes avascular lens & cornea)

Back 19

ciliary processes

Front 20

The ciliary processes are w/i the (ant 1/3 pars plicata/ post 2/3 pars plana) of the ciliary body

Back 20

ant 1/3 pars plicata
(^ arranged in radial folds)

(*ciliary body extends from scleral spur to ora serrata (irreg ant border of retina))

Front 21

Histology of Ciliary epithelium (Vascular layer)

Back 21

-cuboidal, columnar epithelium
-2 layers:
1. outer pigmented- continuous w/ retinal pigmented epithelium
2. inner non-pigmented- secretes aqueous humor (ciliary processes),
pars plana= produces vitreal collagen & hyaluronin,
pars plicata= produces & anchors zonular fibers

Front 22

Histology of Ciliary body stroma (Vascular layer)

Back 22

- vascular CT layer extending into ciliary processes
- contains melanocytes & fibroblasts
- continuation of choroid

Front 23

Histology of Ciliary muscle (Vascular layer)

Back 23

3 groups smooth muscle fibers
1. outer longitudinal- attached to scleral spur, distends into trabecular meshwork= facilitates aq outflow
2. middle radial- attached to inner circular & scleral spur
3. inner circular- anteriorly located, sphincter arrangement

*radial & circular contraction shifts ciliary body forward & inward= decreased zonular fiber tension

Front 24

The ciliary muscle is primarily controlled by ______________

Describe effects of contraction & relaxation

Back 24

postganglionic parasymp from ciliary ganglion (Edgar-Westing nucl)

contraction- suspensory lig relaxes & lens thickens = accomodation

relaxation- muscle moves away from optic axis, suspensory ligament tightens & lens flattens

Front 25

Components of Iris (Vascular layer)

Back 25

* surrounds pupil, controls amount of light that enters, base continous w. ciliary body & connected to cornea via trabecular meshwork
4 Components:
Anterior Border layer
Stroma
Dilator pupillae muscle/ Anterior Epithelial layer
Posterior pigment epithelium

Front 26

Histology of Anterior border layer (Iris, Vascular layer)

Back 26

-no epithelial cells
-uneven discontinuous layer
-contains dense collection of fibroblasts & melanocytes w/ few collagen fibers

Front 27

Histology of Stroma (Iris, Vascular layer)

Back 27

-loose CT w/ fibroblasts, melanocytes, & collagen fibers, & network of blood vessels
-communicates w/ aqueous humor of anterior chamber via openings in anterior border
-contains sphincter pupillae muscle (circular ring of smooth muscle)

Front 28

Fxn of sphincter pupillae muscle

Back 28

annulus of smooth muscle
-contraction decreases pupil size (mitosis)
-supplied by parasympathetic fibers

Front 29

Histology of Dilator pupillae muscle/ Anterior epithelial layer (Iris, Vascular layer)

Back 29

-layer of myoepithelial cells derived from anterior layer of pigment epithelium
- muscular basal portion & epithelial apical portion apposed to posterior pigmented cells

Front 30

Fxn of dilator pupillae muscle

Back 30

radial smooth muscle
-contraction increases pupil size (mydriasis)
-supplied by sympathetic fibers

Front 31

Histology of Posterior pigment epithelium (Iris, Vascular layer)

Back 31

-large cuboidal epithelial cells
-densely pigmented
-extends short distance onto anterior surface at pupillary margin
-layer forms radial folds (most apparent near pupil margin)

Front 32

Explain aqueous humor flow
(produced by ciliary processes)

Back 32

passes from posterior chamber (btwn lens/ciliary body & iris)
--(through zonule & pupil)--> anterior chamber (btwn iris & cornea)
from iridocorneal angle--(through trabecular meshwork)--> drains into scleral venous sinus (canal of Schlemm)

Front 33

Glaucoma= increased resistancce to aqueous humor outlflow & raised intraocular pressure.

Differentiate btwn open angle & closed angle glaucoma

Back 33

open angle- obstruction of trabecular meshwork

closed angle- iris physically blocks inner surface of anterior chamber angle

Front 34

Describe the structure of the lens

Back 34

avascular, biconcave, transpartent structure
3 parts:
-capsule
thickened smooth basement membrane
produced by lens epithelium & lens fibers
completely envelops the lens
-anterior epithelium
simple cuboidal epithelium
equatorial cells elongate & transform into lens fibers
-lens fibers
apical part of fiber migrates anteriorly
basal part posteriorly
deeper/older cells lose nucleus
contain crystallins (specialized proteins)

Front 35

Differentiate btwn ocular & vitreous chambers of the eye

Back 35

ocular chamber-
ant to lens & suspensory ligamens
divided into ant & post chambers by iris

vitreous chamber-
pos 4/5 of eye
btwn lens & retina
contains transparent, avascular vitreous body (gelatinous, composed of water, collagen, hyaluraon)
holds retina in place, supports lens, & transmits light

Front 36

Components of Retinal (inner coat) layer

Back 36

1. retinal pigment epithelium
2. photoreceptor layer
3. external limiting membrane
4. outer nuclear layer
5. outer plexiform layer
6. inner nuclear layer
7. inner plexiform layer
8. ganglion cell layer
9. optic nerve fiber layer
10. internal limiting membrane