Cornea - organogenesis of eye and limb, Biology

Cornea - Organogenesis of Eye and Limb

The fully formed cornea contains 2-cell layered epithelium and the stroma made of extra cellular secreted materials. The bulk of the cornea is build up of the stroma Cornea development. The ectoderm overlying the lens vesicle, containing 2 layers of cells, is the presumptive cornea. The cells of the basal layer divide by mitosis during life to replace those of the upper layer that are shed by desquamation. Under the effect of the lens vesicle the cells of basal layer turns columnar and secrete about 20 layers of type I and type II collagen.

The alternate layers of collagen secreted are parallel to the corneal epithelium but at right angles to each other making an orthogonal ply and constitute the primary stroma among the corneal epithelium and the lens. In the meantime, mesenchymal cells (of neural crest origin) from blood capillaries migrate into this region and make a one-cell thick endothelium that secretes hyaluronic acid into the primary stroma. The stroma swells up and after that into this migrate two waves of mesenchymal cells as well of neural crest origin. These cells then secrete layers of their own collagen forming the secondary or adult stroma. Starting on 10th day of incubation in chick embryo the enzyme hyaluronidase is secreted that destroys the hyaluronic acid and causes the stroma to shrink. The stroma is dehydrated later under the influence of thyroxine secreted through the thyroid gland making it transparent. In the amphibians the outer cornea is made by the epidermal ectoderm and the stroma by this and by inner corneal cells of mesoderm (probably of neural crest origin). The adult cornea is completed during metamorphosis under thyroid influence.

Posted Date: 1/29/2013 2:42:45 AM | Location : United States







Related Discussions:- Cornea - organogenesis of eye and limb, Assignment Help, Ask Question on Cornea - organogenesis of eye and limb, Get Answer, Expert's Help, Cornea - organogenesis of eye and limb Discussions

Write discussion on Cornea - organogenesis of eye and limb
Your posts are moderated
Related Questions
digram or mammalian testis

Q. What do you mean by Insect control? The insects can breed and hide in garbage and other places where there is availability of waste materials. The cockroach lives and breed

Epithelial cells of the kidney proximal tubule ?   A.  The sodium-glucose co-transporter in the luminal membrane is responsible for the net flux of glucose from luminal space to

Define Tertiary level care - Public Nutrition? This is the highest level of health case available to the community for dealing with their most complex health problems, which ca

Explain the Quebec Colony Counter? It is used for counting the number of colonies in a plate. Culture plate is kept on the screen which is illuminated from beneath. Counting is

What are the Advantages of Grains Diabetics should have more grains, beans and starchy vegetables every day. Whole-\ grain foods are nutritious and high in fiber, such as whol

write down the division of cryptogamae and phanerogamae

What is Bidirectional Superior Cavopulmonary Shunt-Bidirectional Glenn Shunt ? Hospital mortality is between 5 and 10 per cent. Early palliation is very good with arterial sat

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

What is the resting membrane voltage of the neuron A complete motor neuron is removed from a frog and placed in normal physiological saline at 1 AM.  The neuron is healthy.  At