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Surface ectoderm forms the lens, corneal epithelium and eyelid. The extracellular mesenchyme forms the sclera, the corneal endothelium and stroma, blood vessels, muscles, and vitreous. The eye begins to develop as a pair of optic vesicles on each side of the forebrain at the end of the fourth week of pregnancy.
An eyelid is a thin fold of skin that covers and protects the eye. The levator palpebrae superioris muscle helps in the movement of eyelid. The human eyelid features a row of eyelashes along the eyelid margin, which helps in protection of the eye from dust and foreign debris. The main function of eyelid is to keep the cornea moist and clean.
When a cornea is needed for transplant, as from an eye bank, the best procedure is to remove the cornea from the eyeball, preventing the cornea from absorbing the aqueous humor. [10] There is a global shortage of corneal donations, severely limiting the availability of corneal transplants across most of the world.
The lens and the epithelium of the cornea arise from the surface ectoderm directly; other structures come from either the neural ectoderm or the neural crest, which itself arises from the ectoderm. The mesoderm has limited contributions: it is the origin of the vitreous body , the blood vessels of the eye, and the extraocular muscles.
A unique feature of most mammal eyes is the presence of eyelids which wipe the eye and spread tears across the cornea to prevent dehydration. These eyelids are also supplemented by the presence of eyelashes, multiple rows of highly innervated and sensitive hairs which grow from the eyelid margins to protect the eye from fine particles and small ...
The corneal endothelium is a single layer of endothelial cells on the inner surface of the cornea. It faces the chamber formed between the cornea and the iris. The corneal endothelium are specialized, flattened, mitochondria-rich cells that line the posterior surface of the cornea and face the anterior chamber of the eye. The corneal ...
The corneal limbus (Latin: corneal border) is the border between the cornea and the sclera (the white of the eye). The corneal surface is one of the body's most specialized structures, undergoing continuous cellular renewal and regeneration. [1] It contains limbal stem cells in its palisades of Vogt.
The cornea is composed of either one or two cuticular layers depending on how recently the animal has moulted. [32] Along with the lens and two humors, the cornea is responsible for converging light and aiding the focusing of it on the back of the retina.