Schematic horizontal meridional section of right eye
V.A.
Cornea
Conjunctiva
Canal of Schelemn
Med. rectus
A.P.
Posterior chamber
Limbus
Chamber
Anterior
iris
Ciliary muscle
Zonula
ciliaris
Lens
Lat. rectus
Ora serrata
Ciliary
body
Vitreous
Lamina
cribrosa
Fovea
Dura
Optic nerve
P.P.
Sclera
Choroid
Retina
Layers
T.Fibrosa
(External
Layer)
T.Vasculosa
(Middle Layer)
T. Nervosa
(inner Layer)
ORGAN OF
VISION
Cornea
Choroid
Ciliary Body
Iris
Eyeball
Lens
Fills
Anterior Chamber
Posterior Chamber
Vitreous Body
Accessory
Structure
(Adnexa)
Sclera
Eye Lids
Tears Gland
Muscles
Retina
TUNICA FIBROSA
A. SCLERA
•
Opaque
•
White
•
Posterior five sixth of the external layer
•
Consists of:
Flat Collagen Bundles
Ground Substance
Fibroblasts
•
Episclera, Tenon’s Space, Tenon’s capsule
•
Suprachoroidal lamina
B. CORNEA
•
•
•
•
Transparent
Colorless
Anterior one sixth of the external layer
Consists of 5 layers:
Layer of epithelium
Bowman’s membrane
Substantia Propria
Descement’s membrane
Endothelium
Avasculer structure, receives its metabolizes by:
diffusion from adjacent vessel and from fluid of the
anterior chamber
Conjunctiva
C
A
B
D
Photomicrographs of a transverse section of cornea. A : The Cornea and
conjuctiva seen at low magnification. B : The posterior corneal epithelium –
also called endothelium (arrows indicate Descemet’s membrane). C :
Conjuntival epithelium.
D : Anterior corneal epithelium. Note the smooth
contour of the surface of this epithelium.
Layers of epithelium:
• Stratified squamos epithelium
• 5-6 cells layers
• Deepest
: columnar
• Next
: polyhydral
• Surface
: flat in shape
Bowman’s membrane:
• A thin layer
• Appears homogenous
• Structureless under the light
microscope
Substantia propria
•
•
90% of the thickness
Composed:
a. Collagenous fibrils arranged in lamellae
(parallel with the surface)
b. Mucoid cement
c. Cells
Descement’s membrane:
• Appears homogenous
• Fibrous protein of collagen type
Endothelium:
• Single layers of cells
• Low cuboidal epithelium
LIMBUS (Corneoscleral Junction)
• Area of transition from transparent collagen bundles of
the cornea to the white opaque fibers of the sclera
• The corneal epithelium, as it passes over into the limbus,
increases in thickness up to ten or more cells
• The
corneal
stroma
losses
its
regular
lamellar
arrangement
• In the stromal layer, irregular endothelium – lined
channels, the trabecular mesh work, merge to form the
canal of Schlemm
Canal of schlemm
Limbus
Cornea
Anterior
chamber
Lens
Ciliary
muscles
Zonule
Iris
Ora serrata
Posterior Ciliary body
chamber and process
Vitreous
body
Photosensitive
retina
Optic
papilla Fovea
Sclera
Choroid
Pigment
epithelium
Choroid
Sclera
Sclera
Diagram of the right eye,
seen
from
above,
showing the structure of
the eye, retina, fovea and
ciliary body. Arrows in the
anterior chamber show
the direction of flow of
aqueous
humor.
An
enlarged diagram of the
fovea is shown at lower
right.
1.Axons of ganglion cells
2.Bipolar cells
3.Rods
4.Cones
Optic nerve
TUNICA VASCULOSA
A. CHOROID
Divided into four layers:
1. The Suprachoroid, lamina suprachoroidea or
epichoroid
Consist of lamellae, each lamella: very thin
membrane
2. Vessel layer (stratum vasculosa)
a. Outer layer
: large vessels
b. Inner layer
: medium sized vessels
3. The capillary layer (Lamina Choriocapillaris).
Serves of nutrition for the outer layers of the retina
4. The lamina Vitrea, lamina elastica / basalis, or
membrane of Bruch:
Non cellular membrane
Two layers:
The outer elastic lamellae, very thin
The inner cuticle lamellae, relatively thicker
Section through retina, choroid and sclera.
Sc
.
1
Ch.
2
3
4
5
6
7
8
9
10
11
12
13
14
Ret
.
Ch = Choroid;
Ret = Retina;
1 = Suprachoroid;
2 = Vessel layer;
3 = choriocapillaris
4 = Lamina vitrea
5 = Pigment epithelium
6 = layer of rods and
cones
7 = external limiting
membrane
8 = outer nuclear layer
9 = outer plexiform layer
10 = inner nuclear layer
11 = inner plexiform
12 = ganglion cell layer
13 = nerve fiber layer
14 = internal limiting
membrane
B. CILIARY BODY
Two zones:
1. The orbiculus ciliaris (Pars Plana)
•
The posterior two thirds
•
Appears darkly pigmented
•
Relatively smooth
2. The corona ciliaris (Pars Plicata)
•
The anterior third
•
Bears some 70 to 80 radially arranged ridges,
the ciliary processes
Circumlental space
Zonula fibers
Lens
Ciliary
processes
Ora serrata
Orbiculus ciliaris
Ora serrata, ciliary body, zonula ciliaris and
lens as viewed from behind after removal of
the vitreous body
C. IRIS
• A thin circular diapraghma
• A circular aperture: the pupil
• Divides the space between the cornea and
the lens into two chambers:
1. The anterior chamber
2. The posterior chamber
Schematic horizontal meridional section of right eye
V.A.
A.P.
Cornea
Posterior chamber
Limbus
Chamber
Anterior
iris
Ciliary muscle
Conjunctiva
Canal of
schelemn
Med. rectus
Zonula
ciliaris
Lens
Lat. rectus
Ora serrata
Ciliary
body
Vitreous
Lamina
cribrosa
Fovea
Dura
Optic nerve
P.P.
Sclera
Choroid
Retina
Layer of iris is five layers:
1. Endothelium
•
A very thin delicate layer
•
Difficult to demonstrate in sections
•
Best shown after treatment with silver nitrate
2. The anterior border layer
The color of the iris upon:
•
The thickness of the anterior border layer
•
And the degree of pigmentation of it cells
In the brown iris:
The layer is thick
The cells heavily pigmented
In the blue iris:
The layer is thin
The cells minimum amount of pigment
3. The vessel’s layer (stroma)
- Consists of a great number of blood vessel
4. M. Sphincter pupillae:
- In the pupillary zone
Contraction: Reduced the diameter of the pupil
- The dilatator pupillae
Contraction: Dilatation of the pupil
5. The pigment epithelium
Horizontal section through pupillary zone of
human iris
Stroma
Anterior border layer
Endothelium
Sphincter pupillae
Pigment epithelium
TUNICA NERVOSA
Consists of two portions :
1. The posterior portion is photosensitive – pars optica
retinae
2. The anterior part is not photosensitive – pars coeca
retinae. Constitutes the inner lining of the ciliary body
and the posterior part of the iris
The retina forms the pars optica retinae. The scalloped
anterior border of the retina is known as the orra serrata.
Epithelium
Choroid
Sclera
Photomicrograph of a section of retina in the transition
(arrow) between the photosensitive (at left) and blind (at
right) parts. This transition is called the ora serrata. Note the
pigment epithelium, the choroid and the sclera.
RETINA
The retina consists of ten layers ,
except at :
1. The fovea centralis
2. The optic disc (optic papillae)
3. The extreme periphery
Canal of schlemm
Limbus
Cornea
Anterior chamber
Ciliary muscles Diagram of the right eye,
Lens
Zonule
Iris
Ora serrata
Posterior Ciliary body
chamber and process
Vitreous body
Photosensitive
retina
Optic
papilla Fovea
Sclera
Choroid
Pigment
epithelium
Choroid
Sclera
Sclera
seen
from
above,
showing the structure of
the eye, retina, fovea and
ciliary body. Arrows in the
anterior chamber show
the direction of flow of
aqueous
humor.
An
enlarged diagram of the
fovea is shown at lower
right.
1.Axons of ganglion cells
2.Bipolar cells
3.Rods
4.Cones
Optic nerve
Development of the retina :
•
The retina derived from an evagination of the anterior
cephalic vesicle or prosencephalon
•
As this co-called optic vesicle comes into contact with
the surface ectoderm, it gradually in vaginates in its
central region forming a double – walled optic cup.
•
In the adult :
a. The outer wall gives rise to a thin membrane
called the pigment epithelium
b. The inner layer is derived the optical or
functioning part of the retina
Diagrams of 4 stages in the development of the eye
Lens Vesicle
Layer of the RETINA :
1. Pigment epithelium
2. Layers of rods and cones
3. External limiting membrane
4. Outer nuclear (or granular) layer
5. Outer flexiform (or molecular) layer
6. Inner nuclear (or granular) layer
7. Inner flexiform (or molecular) layer
8. Ganglion cell layer
9. Nerve fiber layer
10. Internal limiting membrane
RETINA, CHOROID AND SCLERA
4. Collagenous fibers
1. Sclera
5. Chromatophores
2. Choroid
6. Blood vessel
7. Pigment epithelium
8. Rods and cones
9. Outer limiting
membrane
3. Retina
10. Outer nuclear layer
11. Outer plexiform layer
12. Inner nuclear layer
13. Inner plexiform layer
14. Ganglion cell layer
15. Nerve fiber layer
16. Inner limiting
membrane
1. Blood vessels of the
choroid
2. Chromatophores
16. Sclera
17. Suprachoroid layer (lamina
fusca)with chromatophores
18. Vascular layer of the choroid
19. Choriocapillary layer
3. Pigment cells in the
retina
20. Processes of pigment cells
extending between rods and
cones
21. Cones
22. Rod
23. Outer limiting membrane
24. Nuclei of cones
25. Nuclei of rods
4. Rods
5. Cones
6. Outer limiting
membrane
7. Nuclei of cones
8. Nuclei of rods
26. Outer processes of
Muller’s cells
27. Synapses between
horizontal and visual cells
28. Synapses between cones
and bipolar cells
9. Outer plexiform layer
10. Nuclei of bipolar,
horizontal, amacrine
and Muller’s cells
29. Bipolar cell
30. Muller’s cell
31. Amacrine cell
11. Inner plexiform layer
32. Synapses between
processes of bipolar,
amacrine and ganglionic
cells
12. Ganglion cell layer
33. Ganglion cell
13. Muller’s fibers
14. Axons of ganglion
cells
15. Inner limiting
membrane
34. Fiber of optic nerve
35. Horizontal fiber
36. Inner limiting membrane
37. Inner fibers of Muller’s cells
THE ROD CELLS AND THE
CONE CELLS
The rod cells :
• Photo pigment : Visual purple or rhodopsin
• Each retina has about 120 million rods
• Sensitive to light and the receptors used
when low levels of light
The Cone cells :
• Photo pigment : iodopsin
• Each retina has about 6 million cones
• Sensitive only to light of a higher intensity
• Maximum sensitive is in the red, green or
blue of the visible spectrum
Discs
Outer segments
Cilium
Narrow collar
Inner segments
Outer limiting
membrane (Composed
of terminal bars and
filaments of mueller
cells)
Nuclei
Synapses
Mueller cell
cytoplasm
Processes of bipolar
cells
The light and the nervous impulses travel
in the retina
Diagram showing the arrangement of the three layers of
neurons in the retina. Observe that the light and the
nervous impulses travel in opposite directions.
LENS
Transparent
Biconvex, posterior surface has a greater convesity than
the anterior surface
Three structural component :
1. Lens capsule : homogenous
2. Subcapsular Epithelium
 Single layer of cuboidal epithelium cells
 Present only on the anterior surface
3. Lens Fibers :
 Appear as thin flattened structures
 They are highly differentiated cells derived from
cells of the subcapsuler epithelium
The lens, viewed from
behind and from the side.
From section through margin of lens longitudinal sections of lens
fibers and transition from epithelium to lens fibers.
a : Lens fibers; b: capsule; c : epithelium
The lens is held in place by the zonula ciliaris
(Zonula of Zinn, suspensory ligament)
The Zonula on :
1. The lens capsule
2. The ciliary body
The zonula is important in process
accomodation
Connective
tissue
Lens
Anterior view of the
ciliary processes
showing the zonules
attaching of the lens.
Zonule fibers are
bundles of
microfilaments
(oxytalan fibers) from
the elastic fibers
system. The zonules
form column (A) on
either side of the
ciliary processes (B),
which meet on a
single site (C) as
they attach to the
lens.
THE VITREOUS BODY
Transparent gell
Amorphous
Intercellular substance
Bounded by :
The internal limiting membrane of the retina
The lens
The posterior zonular membrane
Accessory structures
A. EYELIDS
1. Hair follicles
10. Superior tarsal
muscle (of Muller)
2. Sweat glands
11. Adipose tissue
3. Epidermis and dermis
4. Rudimentary hari follicle
5. Palpebral part of
orbicularis oculi muscle
6. Connective
tissue
7. Arteriole
8. Ciliary glands : large
sweat glands (of Moll)
9. Sebaceous glands
(of Zeiss)
12. Accessory
lactrimal gland
(of Krause)
13. Lymphatic
tissue
14. Epithelium of palpebral
conjuctiva
15. Tarsal glands
(Meibomian glands)
16. Tarsus
17. Palpebral
conjuctiva
18. Duct of tarsal gland
(Meibomian gland)
19. Ciliary muscle (of Riolan)
20. Hair follicles of eyelashes
B. Lacrimal Apparatus
Consists of :
1. The lacrimal gland
2. Canaliculi
3. Lacrimal sac
4. Nasolacrimal duct
The Lacrimal Gland :
Tear secreting gland
Located in the anterior superior temporal portion of
the orbit
Consist of several separate glandular lobes
Tubulo alveolar
Serous type
Myoepithelial cells surround the secretory portions
LACRIMAL GLAND
6. Venule
1. Glandular
alveoli
2. Intralobular
ducts
3. Myoepithelial
cell (basal or
basket cell)
4. Interlobular
connective
tissue
5. Outpocketing
of glandular
cells
7. Interlobular
duct
8. Glandular
alveoli
9. Interalveolar
connective
tissue
10. Arteries
11. Interlobular
duct
DRAINAGE OF TEARS
Lacrimal Gland
Cornea, Bulbar and palpebral
conjunctiva
Lacrimal Puncta
Lacrimal Canaliculi
Lacrimal Sac
Nasolacrimal Duct
Inferior meatus of nasal
cavity
THE LACRIMAL DRAINAGE SYSTEM