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Fibrous Tunic Of Eyeball
The sclera and cornea form the fibrous tunic of the bulb of the eye; the sclera is opaque, and constitutes the posterior five-sixths of the tunic A tunic is a garment for the torso, usually simple in style, reaching from the shoulders to a length somewhere between the hips and the ankles. It might have arm-sleeves, either short or full-length. Most forms have no fastenings. The name deri ...; the cornea is transparent, and forms the anterior sixth. The term "corneosclera" is also used to describe the sclera and cornea together. References Human eye anatomy {{eye-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Eyeball
The human eye is a sensory organ in the visual system that reacts to visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and keeping balance. The eye can be considered as a living optical device. It is approximately spherical in shape, with its outer layers, such as the outermost, white part of the eye (the sclera) and one of its inner layers (the pigmented choroid) keeping the eye essentially light tight except on the eye's optic axis. In order, along the optic axis, the optical components consist of a first lens (the cornea—the clear part of the eye) that accounts for most of the optical power of the eye and accomplishes most of the focusing of light from the outside world; then an aperture (the pupil) in a diaphragm (the iris—the coloured part of the eye) that controls the amount of light entering the interior of the eye; then another lens (the crystalline lens) that accomplishes the remaining focusing of light into images; ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sclera
The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective outer layer of the eye containing mainly collagen and some crucial elastic fiber. In the development of the embryo, the sclera is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, fatty deposits on the sclera can make it appear slightly yellow. People with dark skin can have naturally darkened sclerae, the result of melanin pigmentation. In humans, and some other vertebrates, the whole sclera is white or pale, contrasting with the coloured iris (anatomy), iris. The cooperative eye hypothesis suggests that the pale sclera evolved as a method of nonverbal communication that makes it easier for one individual to identify where another individual is looking. Other mammals with white or pale sclera include chimpanzees, many orangutans, some gorillas, and bon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornea
The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea Refraction, refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK. While the cornea contributes most of the eye's focusing power, its Focus (optics), focus is fixed. Accommodation (eye), Accommodation (the refocusing of light to better view near objects) is accomplished by changing the geometry of the lens. Medical terms related to the cornea often start with the prefix "''wikt:kerat-, kerat-''" from the Ancient Greek, Greek word κέρας, ''horn''. Structure The cornea has myelinated, unmyelinated nerve endings sensitive to touch, temperature and chemicals; a to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tunic
A tunic is a garment for the torso, usually simple in style, reaching from the shoulders to a length somewhere between the hips and the ankles. It might have arm-sleeves, either short or full-length. Most forms have no fastenings. The name derives from the Latin '' tunica'', the basic garment worn by both men and women in Ancient Rome, which in turn was based on earlier Greek garments that covered wearers' waists. The term is likely borrowed from a Semitic word *''kittan'' with metathesis. The word khiton () is of the same origin. Ancient era Roman tunic The Roman ''tunica'' was adopted by Roman citizens in the 3rd century BCE. It was often worn by Roman citizens and by non-citizens alike. However, citizens might wear it under the toga, especially at formal occasions. The length of the garment, the presence or lack of stripes, as well as their width and ornamentation, would indicate the wearer's status in Roman society. Roman senators, for example, used the '' laticla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
