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Jittipan Chavadej, Ph.D.
Anatomy Department,Fac. of Science
Mahidol University
yr.2000
Mature structures of the eye
Eyeball - cornea & sclera
- lens , eye chamber
- retina , optic nerve
Surrounding muscular structure
- ciliary body
- iris muscles
- extraocular muscles&conjunctiva
Structure of the eye
Formation of the eye
Are formed by 3 different
germ layers.
1. Neuroectoderm
2. Surface ectoderm
3. Mesoderm
Neuroectoderm forebrain(dien.) --> - retina &
optic nerve
- iris &
ciliary body
Surface ectoderm - above
optic vesicle --> lens & cornea
Mesoderm -all CNT & vascular
structures --> choroid layer &
sclera
Retina & Optic nerve form
from optic vesicle
Diagram showing the formation of optic vesicle & the lens
placode
Ventrolateral view off the optic cup & optic stalk showing
the hyaloid artery in the choroid fissure
Retina formation
Changes of inner layer of optic
cup (lens & cornea)
neural retina
Thickening
differentiation
Epith. cells
neurons & light
photoreceptor cells (rods&cones)
Outer layer of optic cup (thin)
pigment layer of the retina
Neural retina (multilayers)
consists of- rods & cones
- bipolar neurons in
inner nuclear layer
- ganglion cells in
ganglion cell layer
Differentiation
•1st-ganglion cell--> optic nerve
•2nd-bipolar neurons & rods - cones
Optic nerve/stalk
Diagram showing the differentiation of layers of the
neural retina.
Diagram showing the
development of the
layers of the neural
retina
Formation of lens
Surface ectoderm lens
lens vesicles
placodes
lens
Differentiation of the lens
•elongation of lens fiber
•contain large amount of crystallin
proteins - alpha,beta & gamma(mol.level)
Invagination
Crystallin(n
o)
Lens cup
Alpha(+/-)
Lens vesicle
Alpha(++)
Beta(+/-)
Gamma(+/-)
Elongation of
10 fiber
Embryonic lens
Alpha(++)
Beta(++)
Gamma(+)
Alpha(+++)
Beta(+++)
Gamma(+++)
Anteroposterior section of the eye showing optic cup,
optic stalk and lens vesicle
Formation of cornea
2 sources-*surface ectoderm
Inductive influence of the lens
-surface ectoderm-
primary stroma :
collagen type I, II, IX
-neural crest cells-corneal endothelium &
secondary stroma (hyaluronic acid-hyaluronidase)
Anteroposterior section through the eye.
Final developmental changes of
cornea= Formation of transparency
-by removing water from secondary
stroma (40%)
-degradation of hyaluronic acid
-thyroxine--> corneal endothelium -
by pumping sodium into antr chamber of
the eye
Iris & Ciliary body formation
-at the lip of optic cup
*Ciliary body -muscle containing
structure + suspensory ligament of
the lens(radial set of muscle) -->modulate
shape of the lens
*Iris -2 sets of muscle(sphincter &
dilator pupillae) -->control the amt of
light passing through the lens
Development of the iris and the ciliary body.The rim of the
optic cup is covered by the mesenchyme, in which the sphinter
and dilator pupillae develop from the underlying ectoderm.
Choroid coat and sclera
Origin = a layer of mesenchymal
cells + neural crest cells outside
the optic cup- under influence of
the pigmented epith. of the retina
Choroid coat-a highly vascular tunic
Sclera-dense collageneous covering
-tough outer coat of the eye
Diagram showing the development of the choroid & the sclera
Vitreous body & Hyaloid artery
Vitreous body-loose mesenchyme
forming a loose fibrillar mesh along with a
gelatinous substance in optic cup
Hyaloid artery-enter the eyeball
through the choroid fissure of the optic
stalk-->retina,vitreous body -->postr wall of
the lens
Note :antr chamber,vitreous cavity-vitreous body
Changes of Hyaloid artery
Regression of hyaloid artery
(in the vitreous body)
Persistance of prox. part of
hyaloid artery as central artery of
the retina
A
C
B
Stages in development
and regression of the
hyaloid artery in the
embryonic eye
Eyelid and Lacrimal gland
7thwk. - fold of skin
9thwk. - meet & temporary fusion
6thmo. -loosening of epith. union
7thmo. - reopening of the eyelid
Conjunctival sac - space betw. the
front of eyeball & eyelid
Lacrimal gl.-multiple epithelial bud
from lateral surface ectoderm
-nasolacrimal duct
-begin to function~6 wk.
after birth
Note : eyelid,iridopupillary membrane & conjunctival sac
Congenital malformations of the eye
 Anophthalmos -absence of an eye
 Microphthalmos -smaller than
normal
 Coloboma iridis -nonclosure of
choroid fissure of the iris