Download MBBS (Bachelor of Medicine and Bachelor of Surgery) 3rd Year (Third Year) Ophthalmology Development of Eye Topic Handwritten Notes
ANATOMY
DEVELOPMENT
? Development of eyebal commenece around day 22
? Eyebal & associated structures are derived from
? Optic vesicle
? Lens placode
? Mesoderm sarrounding optic vesicle
OPTIC VESICLE
? A linear thickened area is formed on the either side of neural plate which is destined to
form the prosencephalon
? Optic sulcus- formed by the depression of the thickened area
? When nural plate get converted to procencephalic vesicle ,the optic sulcus deepens &
the wal overlying the sulcus bulg outwards ,this forms the optic sulcus
? Proximal part of optic vesicle gets constricted to form optic stalk
LENS PLACODE
? Optic vesicle grows lateral y & comes in contact with the surface ectoderm
? An area of ectoderm overlying the vesicle thickens to form lens placode
? Lens placode soon sinks into the vesucle & is converted to lens vesicle
?
OPTIC CUP
? When lens vesicle is formed , the optic vesicle gets converted to optic cup
? This happens due to differential growth of wal of optic vesicle around the lens
? The margins of cup grow over the upper & lateral sides to enclose the lens
? Such growth does not take place in the inferior margin causing a deficiency in the inferior
part coroidal or fetal fissure
? The mesoderm conering the neural tube also covers the optic vesicle
? The mesenchyme differentiate into an outer fibrous & inner vascular layer
DERIVATION OF PARTS OF EYEBALL
? RETINA
? Optic cup is divided into anterior & posterior part
? Anterior part forms epithelium covering for ciliary body & iris
? Posterior part is divided into
? Thin outer wal ---pigmented layer of retina
? Thick inner wal --- nervous retina
? Matrix layer ?rods & cones
? Mantle layer- bipolar cel s ,ganglion celks other supporting cel s
? Marginal layer ? the axons of bipolar cel s grow into marginal layer to form a leyer of nerve fibres
? OPTIC NERVE
? The nerve fibres grow into optic stalk & form optic nerve
? Crystal ine lens
? Lens is fromed from lens vesicle
? Cells in the posterior layer elongates & obliterates the cavity inside, they will lose the nucleus &
froms lens fibres( primary lens fibres)
? Prinary lens fibres form the embryonic nucleus
? Secondary fibres are formed from the eqitorial cells of anterior epithelium which remain active
throughout the life
? Depending on the period of development secondary fibres are named fetal nucleus (3-8 mnth),
infantile nucleus (last week of fetal life ? puberty), adult nucleus(after puberty), cortex (adult
lens)
? cornea
? Epithelium ? formed from surface ectoderm
? Other layers are developed from mesenchyme lying anterior to optic cup
? Sclera
? From fibrous layer of mesenchyme sarrounding optic cup
? Choroid
? From inner vascular layer of mesenchyme sarrounding optic cup
? Ciliary body
? The two layers of epithelium develop from anterior part of optic cup
? Stroma develop from vascular layer of mesenchyme sarrou ding the optic cup
? Iris
? Epithelium derived from marginal region of optic cup
? Sphinncter & dilator pupil ae from the anteror epithelium
? Stroma & blood vessels from vascular mesenchyme
? Vitreous
? Primary vitreous ? mesenchymal orgin & is vascular with hyaloid system of vessels
? Avascular secondary vitreous replaces the primary vitreous, which is secreted by
neuroectoderm of optic cup
? Eyelids
? Formed by reduplication of surface ectoderm
? Two folds are formed & the folds enlarge and meet in midline
? The fold cut some space cal ed conjunctiival sac which entrap some mesoderm, which forms
the muscles of lid & tarsal plate
? Tarsal glands & cilia also develop from the surfac ectoderm
? Conjunctiiva
? Develop from ectoderm lining the globe & lids
? Conjuntival glands also develop as growth of basal cel s in upper & lower fornix
? Lacrimal apparatus
? Lacrimal gland deveop as epithelial buds by the 2nd,month of fetal life in the suoerolateral side
of conjunctiival sac
? Lacrimal sac, nasolacrimal duct & canaaliculi develop from ectoderm of nasolacrimal furrow at
the medial angle of the eye
? Extraocular muscles
? Deveop from the mesoderm around the optic cup
SUMMARY
? surface ectoderm
1.
Lens
2.
Epithelium of cornea
3.
Conjunctiiva
4.
Lacrimal apparatus
5.
Eyelid epithelium, cilia, tarsal glands, conjunctiival glands
? Neural ectoderm
1.
Retina
2.
Epithelial layer of ciliary body& iris
? Sphincter & dilator pupil aele
? opticnerve
? Secondary vitreous
? Mesenchyme
1. Blood vessels of choroid, iris, ciliary vessels, retinal artery, & other vessels
2. Primary vitreous
3. Sclera, ciliary muscles, extraocular muscles
4. Sheath of optic nerve
5. Connective tissue
This post was last modified on 11 August 2021