Development of the visual system

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Last update: Monday, 19 Dec 2022 at 8.52 pm.

This article has been translated from WikiSkripta; ready for the editor's review.

Visual the organ is developing that four sources :

from neuroectoderm at anterior brain ( retina , rear layer iris and vision nerve );
surface ectoderm u ( lens and epithelium corneas );
[[ mesoderm ] ]u ( fibrous and vascular layer eyes );
cells neural slats ( choroid , sclera , endothelium corneas ).

Stages development eyes[edit | edit source]

Development eye is visible from the 22nd day intrauterine development , in neural wallah head the end the germ appears eyes furrows ( grooves ). After merging neural eye rolls _ gutters vychlipi , whereby they create eye ramparts . Connection with the front gradually through the brain tapers into shape ocular stopwatch . At the same time is running out and to changes surface ectoderm head - his part adjacent to the eyes the sacs are thickened , whereby arise the so- called eye placodes . Then occurs to their intussusception in the form of " lenticular ". jamek and with continuing by pinching theirs edges together _ zoom in , merge into lenticular pouches and thereby is losing connection with surface ectoderm . Ocular pouches will create double layered ocular cups ( initially they close the so- called intraretinal space ), whose edges gradually they start veer around lenses . On the ventral side eye cups and on the spot their stopwatches appear _ notches - fissurae optics containing vascular mesenchyme , ze which the [[arteria hyaloidea ] ] ( supplying internal layer eye cups ) and vena hyaloidea . Distal sections these vessel degenerate , however proximal they remain such as the artery and vein centralis retinae.

Development retina[edit | edit source]

Retina develops that walls of the eye cup , external layer of the eye cup contains cells with small pigmented grains and gives arise pigmented layer retina . Rear four fifths this one layers they give arise pars optica retinae, is formed cells reversed to intraretinal space that gradually _ _ they differentiate into rods and cones . To this one layer photoreceptors adjoins mantle layer comprising external nuclear layer which make up cores sticks and cones , and internal nuclear layer formed bipolar cells and a layer ganglia cells . On the inside surface are located axons nervous cells that converge _ _ in visual nerve passing through ocular stem . Front a fifth internal layers of the eye cup gives arise pars caeca retinae, contains amended ganglia cells , but no longer rods and cones . This layer is subsequently divides in pars iridica retinae giving arise internal layer irises and in pars ciliaris retinae, ze which arises ciliated body .

Development of corpus ciliare[edit | edit source]

Pigmented part ciliary epithelium has its origin in the external sheet of the eye cup ( hence further turns into pigment epithelium retina ), opposite to that unpigmented part epithelium represents a continuation of the pars nervosa of the retina , which it does not contain neurons . Muscle ciliaris ( his by contraction changes optical Properties lens ) differentiates from mesenchyme lying down on edge of the eye a cup .

Development irises[edit | edit source]

iris differentiates from the rim of the eye a cup that retracts _ in and partially so overlaps lens . Both layers of the eye cup here they remain thin , iris stroma has its cell origin _ neural slats . The Musculus dilatator pupillae and the musculus sphincter pupillae originate from the neuroectoderm of the eye a cup .

Development lenses[edit | edit source]

lens develops from the lenticular pouch ( i.e. from the surface ectoderm ), cells in her front the wall too they do not change and become subcapsular epithelium lenses . Cylindrical cells rear walls they are losing own cores and occurs their _ transform into long fibers . Thus arise primary fibers lenses . With theirs growth obliteration occurs _ cavities lentil pouch . Cells equatorial zones lenses are gaining cubic shape , they lose cores and changes secondary fibers lenses .

Development choroids , sclerae and corneas[edit | edit source]

Basis eyes are on end the fifth weekly intrauterine development surrounded by mesenchyme , which subsequently _ will divide in two layers - external , which gives arise white and substantial parts cornea , and internal , which differentiates into the choroid , iris and ciliary body body .

Development corneas[edit | edit source]

Front epithelium cornea has origin in the surface ectoderm , considerable part corneas arises from mesenchyme , which has origin in mesoderm . Corneal the endothelium differentiates from the cells neural slats .

Development choroids and sclera[edit | edit source]

Mesenchyme reacts on inductive signals pigmented epithelium retina and thus differentiates _ on internal vascular layer and outer fibrous layer ( bleach ).

Development eye chambers[edit | edit source]

Between basis lens and cornea there is a gap mesenchyme , whereby arises anterior chamber ocular . Externally layer spaced out mesenchyme is formed in the substantia propria corneae , inner ( membrana iridopupillaris ) is the basis for the iris stroma . Rear chamber the eye ' arises in space before lens for iris . After disappearing pupillary membranes then is running out to communication between both chambers .

Development eye lid[edit | edit source]

Emergence lid we can observe from the sixth week , they differentiate from the cells neural slats . They create cutaneous folds overlapping cornea , on the beginning the tenth weekly intrauterine development to each other they grow and separate only in the 26th- 28th week . Algae , as well so glands arise from the surface ectoderm , ligament and tarsal discs they have origin in mesenchyme of the eye eyelids . The Musculus orbicularis oculi arises from the second pharyngeal arc and is therefore innervated n . facialis .

Development tears gland[edit | edit source]

Tearful the gland develops from the lobes surface ectoderm . At birth they are glands small , non -functional ( approximately until the sixth of the week ). From this reason newborn at screaming he doesn't cry . < noinclude >