Outer Fibrous & Middle Vascular Tunic Flashcards
T/F
THE EYE IS A Very complex and delicate organ consisting of many
tissues which protect optic nerve and photoreceptor cells
TRUE
The eye is Located in the skull cavity and is surrounded by _____
muscle and _____ tissues
fibrous; lipoidal
t/f
A normal human eye can see about 1 million different
colors
f; 10 million
Cornea and sclera are connected by a ring called
limbus
conveys signals of the eye to the brain
Optic nerve
___________________ is the clear fluid contained in the anterior
and posterior chamber
Aqueous humor
_________________ is the clear gel-like fluid in the vitreous
chamber
Vitreous humor
3 main layer of the eyes
Outer fibrous tunic
Middle Vascular tunic
Inner Nervous tunic
Covers the exposed part of the
globe, e.g. cornea (anterior to
the pupil), conjunctiva (anterior
to the sclera)
● Comes directly in contact with
the environment
● Protects eye from external environment
● Located anterior to the cornea
precorneal tear film
lipid/oil layer is produced by
meibomian glans
lipid/oil layer is secreted by
meibomian, zeis & moll glands
The outermost, most superficial layer of the pre-corneal tear film
lipid layer
PCTF
retard evaporation of aqueous
lipid layer
PCTF
PREVENTS OVERFLOW OF TEARS
LIPID LAYER
AQUEOUS LAYER OF PCTF IS PRODUCED BY
LACRIMAL GLAND
PCTF
THICKES LAYER
AQUEOUS LAYER
which layer of pctf nourishes cornea with oxygen?
aqueous layer
aqueous layer of pctf has antibacterial function due to presence of
lysozyme
Aqueous layer of PCTF allows passage of _______________________ after injury
leucocytes
PCTF
Produced by goblet cells
mucin/mucoid layer
PCTF
secreted by conjunctival goblet cells & gland of Manz
mucin layer
PCTF
FUNCTIONS IN LUBRICATION
MUCIN LAYER
PCTF
THINNEST
MUCIN LAYER
Outermost layer of the eye containing cornea and sclera
Outer Fibrous Tunic
T/F
The cornea is 1/6 of the eye
T
T/F
the cornea has blood vessels
F
cornea is avascular
The first transparent medium where light passes through
cornea
The tissue in the cornea absorbs its nutrition and oxygen by ____
diffusion
Cornea is responsible for approximately ______ of focusing power of eye
70%
T/F
Gas-permeable contact lenses can be worn for longer periods than hard contact lenses
T
Describe the prolate shape of cornea
steeper center, flatter periphery
Refractive index of cornea
1.376
Dioptric power of cornea
43.25 D
Anterior anatomical section shape of cornea
Elliptical
Posterior/internal anatomical section shape of cornea
circular
Anterior Radius of Curvature of Central Cornea
7.8 mm
Posterior Radius of Curvature of Central Cornea
6.5mm
Vertical corneal dimension (measurement)
11mm
Horizontal corneal dimension (measurement)
12mm
3 factors for corneal transparency
- Anatomical factors
- Physical factors
- Physiological factors
What factor of corneal transparency:
Epithelium is non-keratinized (nucleated living cells)
Anatomical Factor
What factor of corneal transparency:
Stromal lamellae are regularly arranged
Anatomical
What factor of corneal transparency:
Cornea is avascular
Anatomical
What factor of corneal transparency:
Refractive index of fibers and matrix is the same
Physcal factor
Physiological factor
State where the cornea is partially dehydrated for it to be transparent
Deturgescence
Layers of the cornea
Anterior Epithelium
Bowman’s Membrane
Corneal Stroma
Descemet’s Membrane
Endothelium
Layer of the cornea
50-90 μm
Anterior epithelium
Layer of the cornea
12 μm
Bowman’s membrane
Layer of the cornea
500 μm
Corneal stroma
Anterior epithelium is made up of
Stratified squamous non-keratinized epithelium (5-6
layers containing nerve endings)
T/F
Descemet’s membrane:
5 μm in adult & 2 μm in children
false
2 μm in adult & 5 μm in children
Layers of the cornea that regenerates
Anterior epithelium
Corneal Stroma
Descemet’s membrane
Layers of the cornea that does not regenerate
Bowman’s membrane
Endothelium
Where does regeneration of anterior epithelium occur?
limbus/limbal area
junction between cornea and sclera
limbus/limbal area
t/f
Anterior epithelium is hydrophilic to maintain transparency
F
Anterior epithelium is HYDROPHOBIC to maintain transparency
5-7 layers of cells of anterior epithelium regenerate every ____ days to prevent scar formation
7
Cells in the anterior epithelium
Wing cell layer
Epithelial cells
Basal cell layer
Outer 2-3 layers of anterior epithelium
epithelial cells
Middle 2-4 cell layer of anterior epithelium
wing cell layer
Flat with many microvilli & horizontal nuclei. Joined with desmosomes to prevent tears
from penetrating the cornea
epithelial cells
shape of wing cell layer
polyhedral
t/f
Wing cell layer has deep cells with round nuclei, becomes flatter as cells approach the surface of the
cornea
t
Wing cell layer is Joined together from base to apex by
desmosomes and _____________________________
zonula occludens
Cell in the anterior epithelium:
Tall and columnar cells that often show mitosis
basal cell layer
Lateral cell borders of basal cell layer are joined by
_____________________
desmosomes
basal cell layer is Joined to the basement membrane by
hemidesmosomes
Basement membrane is firmly attached to underlying Bowman zone by _________ filaments
irregular
After injury of basement membrane, attachments may take as long as _____________ to be
reestablished
6 weeks
This extracellular matrix of the cornea is secreted by basal cells and composed of type IV collagen and laminin
Basement membrane
Basemnt membrane is secreted by the
basal cell
Basement membrane is composed of __________________
type IV collagen and laminin
Minute spaces in between basal cells and disappear gradually towards the surface. This may be distended pathologically
lymph spaces
Cell junctions
Zonula occludens (tight junctions)
Zonula adherens (desmosomes)
Hemidesmosomes
Cell junction between wing cells. This encircle the cell & form a seal
which prevents small molecules to pass
zonula occludens
Zonula occludens is also known as
tight junctions
Cell junction between basal cells
Zonula adherens
Zonula adherens is also known as
desmosomes
Cell junction between basal cells and basement membrane
hemidesmosomes
layer of the cornea that is structure less, acellular hyaline stroma
bowman’s membrane
Bowman’s membrane is made up of _______ oriented collagen fibers
randomly
Bowman’s membrane is resistant to trauma and infection. This layer regenerates.
1st statement is true, 2nd statement is false
2nd statement is true, 1st statement is false
both statements are true
both statements are false
1st statement is true, 2nd statement is false
Bowman’s membrane is resistant to trauma and infection. This layer does not regenerate.
layer of cornea with 90% of corneal thickness
corneal stroma
Corneal stroma is also known as
substantia propia
corneal stroma has ____% water content
78%
Corneal stroma compose of lamellae of collagen fibrils arranged in a regular ________ (type I, III, V, VI)
lattice
Examples of wandering cells in corneal stroma
leukocyte
macrophages
Corneal nerves enter peripherally in a _______ pattern into the stroma
radial
Injury to this area will result in extreme pain from the swelling and stretching of those nerves
corneal stroma
what layer of the cornea
true membrane
descemet’s membrane
Descemet’s membrane is made up of type IV collagen fibers arranged in __________ pattern
hexagonal
Descemet’s membrane is not resistant to infection & trauma. It does not regenerate after injury
1st statement is true, 2nd statement is false
2nd statement is true, 1st statement is false
both statements are true
both statements are false
both statements are false
Descemet’s membrane is very resistant to infection & trauma. it regenerates readily after injury
T/F
Endothelium consists of a single layer of flattened/hexagonal cells
with large oval nuclei
T
Endothelium has apices of the cell are in direct contact with the aqueous humor with occasional ___________
microvilli
layer of the cornea where Cells are tightly bound together by desmosomes & tight junctions
endothelium
Responsible for deturgescence of corneal stroma
endothelium
Functions as permeable membrane to bring in oxygen via aqueous while transporting out fluid and
waste product
Endothelium
Not yet included as part of the layers. Anatomically found between corneal storma and descemet’s membrane
Dua’s layer
Opaque network of collagen (fibrous protein) and elastic
fibers
sclera
Sclera covers posterior ___ of the outer coat of the eye
5/6
SCLERA
Thickest in the region surrounding the _______.
optic nerve
sclera
Thinnest immediately in the insertions of the _________
recti muscles
Forms the white of the eye
sclera
Sclera is covered with:
episclera
fascia bulbi (tenon’s capsule)
conjunctiva
Sclera is opaque white due to:
variable diameter of collagen fibers
irregular arrangement of collagen fibers
high water content
3 main functions of sclera
Protects
Maintains shape and exact position of diff parts of the optic system
Provides rigid insertion and serves as attachment sites for EOM
Give the color of sclera:
- Children, scleral thinning
- Old
- high refractive power
- bluish
- yellowish
- bluish
Sclera appears bluish in children due to the underlying ______ and the sclera not yet fully developed
choroid
appears bluish among people with high refractive power due to _____________________________________
stretching and continuous elongation
Sclera appears yellowish in the older population due to
___________
fatty deposits
Layers if the sclera
episclera
scleral stroma
lamina fusca
layer of the sclera
Moderately dense, vascular CT that merges with scleral stroma. The anterior portion has rich blood supply. Blood vessels are inconspicuous (not visible) except
when inflamed
Episclera
scleral inflammation wherein blood vessels are visible
scleritis
Layer of the sclera with bundles of typical collagen fibers (type I & III)
scleral stroma
Scleral stroma is white because the collagen fibers have:
- Variable diameter
- Irregular arrangement
- High water content
- With fibroblast and pigment cells
Layer of the sclera
- Innermost layer
- Formed mainly of elastic fibers & fine collagen fibers
- Brown color due to the melanocytes from the choroid
lamina fusca
lamina fusca is brown due to the ____________________ from the choroid
melanocytes
Middle layer of the eye. Consists of Choroid, ciliary body & iris
Middle vascular tunic
Highly pigmented coat lining the sclera
choroid
Structure connecting choroid & iris. Lined by the ciliary part of the retina
Ciliary body
Parts of the ciliary body
Pars plana
Pars plicata
Part of the ciliary body near the choroid
pars plana
part of the ciliary body: smooth ciliary ring
pars plana
part of the ciliary body: ridged crown
pars plicata
Ciliary body contains:
Ciliary muscle
Ciliary processes
Ciliary muscles comprises 2 sets of smooth muscle fibers which are
longitudinal fibers
Oblique fibers
smooth muscle fiber in the ciliary muscle that connect sclera to choroid
longitudinal fibers
smooth muscle fiber in the ciliary muscle that enter the base of ciliary processes
oblique fibers
smooth muscle fiber in the ciliary muscle Supplied by parasympathetic fibers by the way of ciliary nerves
oblique fibers
Contraction of oblique fibers makes ciliary body move _________
anteriorward
Ciliary processes are about a. _____in number. Arranged in a circle posterior to the b. _______
- Site of secretion of c. ____________
a. 70
b. iris
c. aqueous humor
Circular, pigmented diaphragm. Lies anterior to the lens in a coronal plane
iris
Iris has a pattern of radial striations that is unique from one
individual to another.
t/f
t
Iris is anchored ____________ to the ciliary body
peripherally
2 chambers divided by iris between cornea and lens
Anterior chamber
posterior chamber
Chamber bounded by cornea and iris
anterior chamber
chamber filled with aqueous humor
Anterior chamber and Posterior chamber
chamber bounded by iris, ciliary process, zonule, crystalline lens
posterior chamber
Parts of the iris
Collaterette
Stroma
SPhicter pupillae
Dilator pupillae
Anterior surface of the iris
collarette
Part of the iris
Normally contains melanin pigment
stroma
Color of eyes with low melanin amount
blue
COlor of eyes with high melanin amount
brown
Situated in the posterior part of the iris, near the
pupil
sphincter pupillae
what type of muscle does sphincter pupillae have?
smooth muscle
Sphincter pupillae is supplied by parasympathetic fibers by way of
short ciliary nerves
Contraction of sphincter pupillae muscle results in pupillary
constriction (miosis)
what drug is placed on the eye which annuls the action of ciliary muscle and sphincter pupillae
(both are under parasympathetic control)
atropine-like
Consists smooth muscle anterior to the pigmented epithelium on the posterior aspect of the iris, which constitutes iridial part of the retina
Dilator pupillae
Dilator pupillae is supplied by ____________ fibers
sympathetic
Contraction of dilator pupillae results in _____ of the pupil
dilation (mydriasis)
Sympathetic innervation arises as preganglionic nerves leaving the spinal cord in the upper 4 thoracic
_________
ventral roots
transmit the sympathetics to the gangliated chain and the preganglionic fibers enter and ascend the cervical sympathetic chain
White rami
Dilator pupillae
Sympathetic preganglionic fibers synapse in the
superior cervical ganglion
Nerve fibers in the dilator pupillae follow the _____________ and ___________ to reach the eye
internal carotid;
ophthalmic arteries
Congenital, radial defect of the iris
coloboma
What is the radial muscle of the iris?
dilator pupillae
What is the circular muscle of the iris?
iris sphincter
Accompanied with a small (meiotic) pupil and slight
drooping of the upper eyelid due to paralysis of the
superior tarsal muscle
horner’s syndrome
