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The front part is also called the anterior segment of the eye. The eye is not shaped like a perfect sphere; rather it is a fused two-piece unit, composed of an anterior (front) segment and the posterior (back) segment. The anterior segment is made up of the cornea, iris and lens.
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.
The iris (pl.: irides or irises) is a thin, annular structure in the eye in most mammals and birds that is 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. Eye color is defined by the iris.
The cranial region includes the upper part of the head while the; facial region includes the lower half of the head beginning below the ears. The forehead is referred to as the frontal region. The eyes are referred to as the orbital or ocular region. The cheeks are referred to as the buccal region. The ears are referred to as the auricle or ...
There are two important foramina, or windows, two important fissures, or grooves, and one canal surrounding the globe in the orbit. There is a supraorbital foramen, an infraorbital foramen, a superior orbital fissure, an inferior orbital fissure and the optic canal, each of which contains structures that are crucial to normal eye functioning.
The sclera's blood vessels are mainly on the surface. Along with the vessels of the conjunctiva (which is a thin layer covering the sclera), those in the episclera render the inflamed eye bright red. [6] In many vertebrates, the sclera is reinforced with plates of cartilage or bone, together forming a circular structure called the sclerotic ring.
With this simple geometrical similarity, based on the laws of optics, the eye functions as a transducer, as does a CCD camera. In the visual system, retinal, technically called retinene 1 or "retinaldehyde", is a light-sensitive molecule found in the rods and cones of the retina.
Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil. This is known as the pupillary light reflex. The iris contains two groups of smooth muscles; a circular group called the sphincter pupillae, and a radial group called the dilator pupillae. When the sphincter pupillae contract ...