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Humans have two eyes, situated on the left and the right of the face. 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 ...
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.
The uvea (/ ˈ j uː v i ə /; [1] derived from Latin: uva meaning "grape"), also called the uveal layer, uveal coat, uveal tract, vascular tunic or vascular layer, is the pigmented middle layer of the three concentric layers that make up an eye, precisely between the inner retina and the outer fibrous layer composed of the sclera and cornea.
The mouth is referred to as the oral region. The chin is referred to as the mental region. The neck is referred to as the cervical region. The trunk of the body contains, from superior to inferior, the thoracic region encompassing the chest [1] the mammary region encompassing each breast; the sternal region encompassing the sternum
The human choroid is thickest at the far extreme rear of the eye (at 0.2 mm), while in the outlying areas it narrows to 0.1 mm. [1] The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract.
Different species are able to see different parts of the light spectrum; for example, bees can see into the ultraviolet, [55] while pit vipers can accurately target prey with their pit organs, which are sensitive to infrared radiation. [56] The mantis shrimp possesses arguably the most complex visual system of any species. The eye of the mantis ...
The resulting eye is a mixture of a simple eye within a compound eye. Another version is a compound eye often referred to as "pseudofaceted", as seen in Scutigera . [ 28 ] This type of eye consists of a cluster of numerous ommatidia on each side of the head, organised in a way that resembles a true compound eye.
The globe of the eye, or bulbus oculi, is the frontmost sensory organ of the human ocular system, going from the cornea at the front, to the anterior part of the optic nerve at the back. More simply, the eyeball itself, as well as the ganglion cells in the retina that eventually transmit visual signals through the optic nerve.