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The eyes sit in bony cavities called the orbits, in the skull. There are six extraocular muscles that control eye movements. The front visible part of the eye is made up of the whitish sclera, a coloured iris, and the pupil. A thin layer called the conjunctiva sits on top of this. The front part is also called the anterior segment of the eye.
A peg cell is a non-ciliated epithelial secretory cell within the uterine tube (oviduct or fallopian tube). [1] These cells represent one of three epithelial cell types found within the normal fallopian tube epithelium and only make up around 10% of the total number of cells. The other two cell types are ciliated columnar and intercalary cells. [1]
A refractive cornea type eye of a human. The cornea is the clear domed part covering the anterior chamber of the eye. In the eyes of most mammals, birds, reptiles, and most other terrestrial vertebrates (along with spiders and some insect larvae) the vitreous fluid has a higher refractive index than the air. In general, the lens is not spherical.
Human eyes are somewhat distinctive in the animal kingdom in that the sclera is very plainly visible whenever the eye is open. This is not just due to the white color of the human sclera, which many other species share, but also to the fact that the human iris is relatively small and comprises a significantly smaller portion of the exposed eye ...
Cells from both the mesodermal and the ectodermal tissues contribute to the formation of the eye. Specifically, the eye is derived from the neuroepithelium, surface ectoderm, and the extracellular mesenchyme which consists of both the neural crest and mesoderm. [2] [3] [4] Neuroepithelium forms the retina, ciliary body, iris, and optic nerves.
The limbal ring is a visible dark ring around the iris of the eye composed of darkened areas of the corneal limbus. The outermost epithelial cells are regularly shed and must be replenished through cell proliferation. The cornea is composed of three primary cell types: epithelial cells, corneal fibroblasts, and endothelial cells. [1]
The interior of the eye lacks lymph vessels but is highly vascularized, and many immune cells reside in the uvea, including mostly macrophages, dendritic cells, and mast cells. [1] These cells fight off intraocular infections, and intraocular inflammation can manifest as uveitis (including iritis) or retinitis. The cornea of the eye is ...
Peg laterals typically occur on both sides, [2] and have short roots. [2] Inheritance may be involved, [ 2 ] and the frequency of microdontia in the upper laterals is just under 1%. [ 1 ] The second most commonly involved tooth is the maxillary third molars, [ 3 ] and after this supernumerary teeth .