The development of the eye begins around day 22 of gestation with the formation of optic grooves on either side of the forebrain, which then invaginate to form optic vesicles. The optic vesicles continue to develop into double-walled optic cups with inner and outer layers. Simultaneously, surface ectoderm thickens to form lens placodes which then invaginate to form lens vesicles. The optic cups and lens vesicles continue to develop throughout weeks 4-8 of gestation, with structures such as the iris, ciliary body, retina, choroid, and sclera deriving from the optic cup layers and the lens developing from the lens vesicle. By week 8, the basic structures of the eye

1. Dr. Najma Baseer
MBBS, MHPE, PhD
Associate Professor Anatomy
IBMS, KMU

2.  Development of internal ear
 Development of utricle and semicircular canal
 Development of cochlea
 Development of organ of corti
 Development of middle ear
 Development of ossicles
 Development of external ear

3.  Around day 22 otic placodes formed in the head region
 lying behind the second pharyngeal arch.
 Ectoderm thickens each side of rhombencephalon
 Sides invaginate form otic/auditory vesicles (AKA otocysts)
Otic Placode @22nd day on
each side of hindbrain
Invaginatingplacode Oticpit Oticvesicle Forms membranous labyrinth

5.  Otocystic cells of vesicles differentiate into ganglion cells for vestibulocochlear/ statoacoustic
ganglia
 Each vesicle divides, forming two components that will become membranous labyrinth
 Ventral component: forms saccule, cochlear duct (for hearing)
 Dorsal component: forms utricle, semicircular canals, endolymphatic duct (for balance)

6. • Flattened outpouchings appear on dorsal component/utricle of otic vesicle
• Central portion of their walls eventually disappear, semicircular canals develop
• Three pairs of SCD are formed –Ant/Post/Lat
• One end of SCD form dilatation (Crus Ampullare) and the other does not widen (Crus
Nonampulare)
• Because two crus nonampullare fuse, there will be 3 crus ampullare and 2 crus nonampullare

7. Week 6
 Saccule forms tubular outgrowth; cochlear duct
 Cochlear duct spirally penetrates mesenchyme
 Completes 2.5 turns by week 8
Week 7
 Cochlear duct cells give rise to spiral organ of Corti
 Cochlear duct remains connected to saccule via ductus
reunions
 Mesenchyme surrounding cochlear duct differentiates
into cartilaginous shell
Week 10
 Large vacuoles appear in cartilage
 Form two peri-lymphatic spaces
 Scala vestibuli
 Scala tympani

8.  Cochlear duct now separated from scala
vestibuli by vestibular membrane, from
scala tympani by basilar membrane
 Lateral wall of cochlear duct remains
attached to cartilage by spiral ligament
 Median angle of cochlear duct connected to
cartilaginous process called modiolus

9.  Within the cochlea, the specialized structure required for converting mechanical vibration into an
electrical signal occurs at the Organ Of Corti
 Epithelial cells of cochlear duct form two ridges
 Inner ridge gives rise to spiral limbus
 Outer ridge gives rise to sensory hair cells of
auditory system
 Tectorial membrane covers sensory cells while
attached to spiral limbus

11.  Composed of
 tympanic cavity
 Eustachian tube/Auditory tube
 Tympanic cavity develops from first pharyngeal
pouch/endoderm
 Pouch expands, reaches floor of first
pharyngeal cleft
 Distal part of pouch widens, becomes primitive
tympanic cavity
 Proximal part remains narrow, becomes
auditory tube

12.  Appear during the first half of fetal life
 Remain embedded in mesenchyme until it dissolves in 8th month
 Derived from separate origins in the first and second arch mesenchyme.
Malleus and incus
 Derived from cartilage of first pharyngeal arch
 Tensor tympani muscle innervated by mandibular branch of trigeminal nerve
Stapes
 Derived from cartilage of second arch
 Stapedius muscle innervated by facial nerve
 In addition there are two muscles (tensor tympani and stapedius) formed from
arch mesenchyme.

13.  External ear is derived from 6 surface
hillocks (auricular hillocks), three on each of
pharyngeal arch 1 and 2.
 External auditory meatus derived from
dorsal portion of first pharyngeal cleft
 During third month, epithelial cells of
meatus' floor proliferate, form solid
epithelial plate (AKA meatal plug)
 During seventh month meatal plug
dissolves, creating definitive eardrum
 Meatal plug persists until birth -congenital
deafness

14. • Human embryonic head from week 5 (stage 14) through to week 8 (stage 23) showing development of
the auricular hillocks that will form the external ear.
• The adult ear is also shown indicating the part of the ear that each hillock contributes.
• develops from six aural hillocks: 3 on first pharyngeal arch and 3 on the second pharyngeal arch.
• Originally on neck, moves cranially during mandible development

15.  Ectodermal epithelial lining of auditory meatus
 Endodermal epithelial lining of tympanic cavity
 Intermediate mesoderm layer of connective tissue
Auricle
 Auricle develops from six mesenchymal proliferations/auricular hillocks
at dorsal ends of first, second pharyngeal arches surrounding first
pharyngeal cleft
 These proliferations later fuse, form definitive auricle

16. Pharyngeal Arch Hillock Auricle Component
Arch 1 1 tragus
2 helix
3 cymba concha
Arch 2 4 concha
5 antihelix
6 antitragus
External ear simplified anatomy

17. At Birth Adult

18. Embryonic structures AdultDerivatives
Otic vesicle
Saccularportion
Utricularportion
Saccule, CD,Spiralganglion
Utricle, SCD, vestibular ganglionand
endolymphatic duct
Pharyngeal
membrane1
Tympanicmembrane
Arch1 Malleus, Incus, Tensortympani
Arch2 Stapes, Stapedius
Pouch1 Middle ear cavity and auditorytube
Pharyngeal cleft1 External acousticmeatus
6auricularhillocks Pinna
Middl
ear
Ext
ear
Internal
ear

20.  Middle of Week 4 to Middle of Week 8, Myelination of optic nerve continues after birth

21. (Diencephalon)

Optic Grooves

Optic Vesicles

Optic Cups
[AKA Neuroectoderm]
Prosencephalon
Neuroepithelium
Lens
Placode
Optic
Vesicle
Mandibular
Arch
[diencephalon]
 Day 22: begins with formation of optic grooves on both
sides of forebrain
 As neural tube closes, optic grooves form outpouchings
(optic vesicles)
 Optic vesicles grow out laterally from the
diencephalon.
 The cavity of each optic vesicle is continuous with the
ventricular cavity of the diencephalon.
 The surface ectoderm will give rise to:
 Lens placode from which the lens will develop
 Epithelium of the cornea.

22. M & P 19 - 1
≈22 days
≈28 days
≈32 days
• Optic vesicles invaginate become double-
walled with an outer and an inner layer
separated by the intra-retinal space
• Optic vesicles form double layered optic
cups
• Inferior surface of optic cup forms choroid
fissure pathway for hyaloid artery
• Week 7: choroid fissure closes, gives rise to
pupil
• Ectoderm cells elongate, form lens placode
• Lens placode invaginates, forms lens vesicle

23. M & P 19 - 1
≈22 days
≈28 days
≈32 days
• The proximal portion of the optic vesicle becomes
constricted to form the optic stalk which differentiates
into the optic nerve.
• Optic nerve is a fiber tract of the diencephalic portion of
the brain.
• The optic or choroid fissure is a linear indentation on
the ventral aspect of the developing optic cup and optic
stalk.
• The blood vessels (hyaloid artery) travel in this fissure.
• The Optic Vesicles induce the surface ectoderm to form
the lens placode.
• It acquires a depression or lens pit which enlarges to
form the lens vesicle.
• The lens vesicle pinches off from the surface ectoderm
as the lens is formed.

24. M & P 19 - 3
Edges of the
pupil
• Optic nerve arises from optic stalk, which
connects optic cup to brain
• Optic or Choroid Fissure gradually closes
leaving a round opening facing the
developing lens, i.e. the PUPIL of the eye.
• OPTIC NERVE composed of the axons of the
ganglion cell layer of the neural retina
• As these axons proliferate, they obliterate
the lumen of the optic stalk.
• Central artery and vein of the retina end up
in the center of the optic nerve.

25. M & P 19 - 3
Edges of the
pupil
• Sheath of the optic nerve forms from surrounding
mesenchyme.
• It is continuous with the meninges of the brain
and the choroid/sclera of the eye.
• Increased intracranial pressure leads to swelling of
the optic disc, i.e. papilledema, because of the
continuity of these ensheathing membranes.
• Myelination of the optic nerve: incomplete at birth,
so it takes awhile for a newborn to really see their
visual world.
Contents of optic nerve
• Inner layer provides neuroglia, supports optic
nerve fibers
• Hyaloid artery later transforms into central artery
of retina

26. M & P 19 - 8
Mesenchyme
• Retina, Ciliary Body and
Iris develop from the
neuroectoderm of the optic
cup.
• Lens develops from surface
ectoderm

27. Note: Intraretinal space is eliminated by fusion of the
pigment layer with the neural layer of the retina.
Developing pigment
epithelium of the
retina [from outer
layer of optic cup]
Developing neural layer of
the retina [from inner layer of
optic cup]
Neural layer
of the retina
Central
artery of
retina
Intraretinal
space
Pigment
epithelium of
the retina
A B
C D
Mesenchyme
Ora serrata located
about here
•Outer layer of optic cup >> pigment layer of
retina
•This developing layer has a strong
inductive influence on the development of
the neural retina, choroid and sclera.
•Inner layer of optic cup >> neural layer of
retina (rods, cones, bipolar cells, ganglion
cells)
•Intraretinal Space
•Ora Serrata = junction of neural retina
with ciliary body.
•Hyaloid artery & vein >> Central artery &
vein of retina.
•The portion of these vessels that lies within
the vitreous regresses during fetal life (“D”
in this slide) since the lens will become
avascular in the adult.
Hyaloid
artery of
retina

28. 3.5 wks 4 wks 5 wks
6 wks 6.5 wks 8 wks
Neural layer
of the retina
Pigment
epithelium
layer of the
retina
Optic Vesicle
Intraretinal
space
Lens
Vesicle
Lens Lens
Lens
Pit
Lens
Mesenchyme
Diencephalon
Inner layer of
optic cup
Outer layer
of optic cup
Optic
Cup

29. Ciliary Body
Central artery
of retina
A B
C D
Lens
Lens
Lens
Lens
Iris
Mesenchyme
Ora serrata located
about here
Iris
NEXT
SLIDE
• Develop from the inner & outer layers of the optic cup -- anterior to the ora serrata.
• Pars iridica retinae: forms inner layer of Iris
• Pars ciliaris retinae: forms ciliary body
Three layers
• Outer, pigmented layer of optic cup
• Inner, neural layer of optic cup
• Richly vascularized connective
tissue layer containing pupillary muscles
• Sphincter, dilator pupillae develop
from ectoderm of optic cup

30. From
mesenchyme
Primary
(posterior)
lens fibers
Anterior lens
fibers
Anterior chamber
Posterior
chamber
Ciliary
epithelium
[pigmented &
non-pigmented
• Pigmented & non-pigmented layers of ciliary epithelium that cover the ciliary processes develop from the outer
& inner layers, respectively, of the optic cup.
• Ciliary muscle (smooth muscle) develops from surrounding mesenchyme.

31. 3.5 wks 4 wks 5 wks
6 wks 6.5 wks 8 wks
Lens
Lens
Pit
Lens
Anterior
layer of
the Lens
Posterior
layer of
the Lens
Lumen
within the
Lens
Vesicle
Mesenchyme
Optic Vesicle
Diencephalon
Area of the
Lens
Placode
Note that
lumen
disappears
Remnants of
hyaloid
vessels
• lens placode  lens pit  lens
vesicle lens
• Lens placodes are not yet obvious
in “a”
• Inductive influence of the optic
vesicles contacting the surface
ectoderm causes the formation of
lens placodes
• Anterior layer of the lens vesicle
remains thin and forms the
subcapsular lens epithelium on
the anterior surface of the lens
• Posterior layer of the lens vesicle
gives rise to the primary lens
fibers which elongate to fill (and
eliminate) the lumen of the
vesicle.
• Primary lens fibers lose their
nuclei and must last a lifetime.

32. 3.5 wks 4 wks 5 wks
6 wks 6.5 wks 8 wks
Lens
Lens
Pit
Lens
Anterior
layer of
the Lens
Posterior
layer of
the Lens
Lumen
within the
Lens
Vesicle
Mesenchyme
Optic Vesicle
Diencephalon
Area of the
Lens
Placode
Note that
lumen
disappears
Remnants of
hyaloid
vessels
• Lens epithelial cells in the
equatorial zone (or outer rim of
the lens) serve as a stem cell
population from which new
secondary lens fibers are formed
throughout life
• These secondary lens fibers are
added to the lateral aspects of
the primary fibers.
• The lens is avascular in the
adult; it depends upon diffusion
from the aqueous humor.
• Remnants of the hyaloid vessels
in “d” and “e”.

33. Vitreous
Central artery
of retina
Hyaloid
canal
Irido-pupillary
membrane
Irido-pupillary
membrane
Posterior
chamber
Posterior
chamber
Future Anterior
chamber
Anterior
chamber
Anterior
chamber
Mesenchyme
Hyaloid
artery
[aqueous
humor]
[aqueous
humor]
[aqueous
humor]
[aqueous
humor]
• Anterior Chamber appears as a space in the mesenchyme between the developing lens and cornea.
• Posterior Chamber forms as a
space in the mesenchyme
posterior to the developing iris
and anterior to the developing
lens.
• Both chambers are filled with
aqueous humor that is secreted by
the ciliary processes.
• Vitreous Body is transparent and
gelatinous; it differentiates from
mesenchyme lying between the
lens and retina.
• Hyaloid Canal: Hyaloid vessels
that pass through the vitreous
early in development to supply the
posterior aspect of the lens vesicle,
regress during fetal life, leaving
behind the ‘hyaloid canal’.

34. Vascular
plexus of the
choroid layer
Sclera
Mesenchyme
Sheath of the
optic nerve
• Choroid and Sclera form from surrounding mesenchyme.
• Inner layer is the vascular & pigmented CHOROID. Comparable to pia-arachnoid.
• Outer layer is the tough SCLERA. Comparable to dura.
• Continuous with the sheath of the optic nerve, posteriorly.

35. Epithelium
Mesenchyme Surface
Ectoderm
3 layers of the
cornea
Stroma
Endothelium
•Three layers of the cornea & conjunctiva
form at the most anterior aspect of the eye.
• Surface ectoderm induced by lens to
form the epithelium of the cornea &
conjunctivum.
• Stroma is derived from mesenchyme.
• Endothelium forms from the
mesenchymal lining of the anterior
chamber.

36. Epithelium
Stroma
Endothelium

37. Eyelids fused
by Wk 10
Mesenchyme
Surface
Ectoderm
Eyelids re-opened
by ~26 wks.
Transverse folds of surface
ectoderm + mesenchyme
begin to form in Week 6.
• Muscles & Nerves of the Eyelids:
• Skeletal muscle
– Orbicularis oculi (2nd arch; facial)
– Levator palpebrae superioris (pre-otic myotomes;
oculomotor)
• Smooth muscle
– Superior tarsal (mesenchyme; sympathetics)

38. Balloon-Like Congenital Cataract
Congenital Familial Central Cataract
Etiologies:
• Rubella infection of mom at 4 - 7 wks gestation
• Hereditary
• Malnutrition
• Chromosomal abnormalities
• Radiation
• Galactosemia
Lens becomes opaque during intrauterine life.

39. • Disruption of the adhesion between the neural and pigmented layers of the retina.
• These examples in the adult.
• During development, congenital detached retina appears to be:
• due to failure of the retinal layers to fuse and obliterate the intraretinal space.
• caused by unequal growth of the eye.
Iris of right eye
Retina
Iris of right eye

40. A. Disturbed development of the levator palpebrae
superioris and/or its oculomotor (GSE) innervation.
B. Surgically corrected
C. Autosomal dominant trait
Iris of right eye
Retina
Iris of right eye
A B

41. • Defective closure of the choroid or optic fissure
• Position: infero-nasal quadrant reflective of the
location of the optic fissure during development
Iris of right eye
Iris of right eye
Iris of right eye
Retina of right eye