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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 . Arizona Eye Model. "A" is accommodation in diopters. The eye can be considered as a living optical device. It is approximately spherical in shape, with its outer ...
History of research. The human eye, showing the iris and pupil. In 1802, philosopher William Paley called it a miracle of " design ." In 1859, Charles Darwin himself wrote in his Origin of Species, that the evolution of the eye by natural selection seemed at first glance "absurd in the highest possible degree". [ 3]
The iris ( pl.: irides or irises) is a thin, annular structure in the eye in most mammals and birds, responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm.
113, 6734. Anatomical terminology. [ edit on Wikidata] An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system . In higher organisms, the eye is a complex optical system that collects light ...
The sclera forms the posterior five-sixths of the connective tissue coat of the human eyeball. It is continuous with the dura mater and the cornea, and maintains the shape of the eyeball, offering resistance to internal and external forces, and provides an attachment for the extraocular muscle insertions. The sclera is perforated by many nerves ...
[47] [49] The ears are rounded and the eyes have a round pupil. [47] The snout ends in a triangular, pink tip with small black dots, the number of which increase with age. [50] The tiger's skull is robust, with a constricted front region, proportionally small, elliptical orbits, long nasal bones and a lengthened cranium with a large sagittal crest.
The central outermost transparent colorless part of the eye (through which we can see the iris and pupil) is the cornea. Cross-section of the human eye, showing the position of the pupil. The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. [ 1 ] It appears black because light rays entering ...
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in ...