Blue Iridized
What's in the eye: The basic structure of the human eye
First, I think it is important to briefly review some of the relevant anatomy that the human eye .. The cornea is on the front of the eye and is the clear window through which light passes before traveling first through an opening called pupil.
The iris appears as the color of the eye and is responsible for regulating the size of the pupil, which in turn influences the amount of light entering the eye. Finally, in the back of the eye is the retina, a multilayered structure consisting of a variety of cell types, which receives visual stimuli from the environment and transmits this information to the brain via the optic nerve for further processing.
The iris
The iris (plural: iris) Iris is named after the Greek goddess of the rainbow and messenger of the gods. Structurally, the iris contains two different layers. The innermost layer (closest to the back of the eye) is called the iris pigment epithelium, or IPE for short.
The cells of this layer appear as small cubes and stacked in a provision Compact and tidy, like bricks. Moreover, as the name suggests, these pigmented cells appear. The top layer is called the stroma of the iris, which is less orderly and more loosely arranged cells.
There are several types of cells in the stroma, including a specialized population pigmented cells called melanocytes. Melanocytes are cells that synthesize pigment (called melanin) and come from an embryonic structure called the neural crest.
The structural elements that determine the iris color:
There are three main factors related to the structure of the iris that can influence its color:
(1) the pigment in the IPE
(2) the pigment content of the iris stroma
(3) cell density of the iris stroma.
From the above, know that there are two regions in the iris containing pigment, melanin or: one is in the IPE, which I have already escaped, and the other is in the iris stroma. For the most part, the amount and distribution of melanin in the IPE is similar in rainbow colors. Therefore, it is unlikely that IPE is itself an important determinant of iris color.
However, it appears that melanocytes in the iris stroma play an important role. Melanin pigment cells in your shop specialized organelles called melanosomes. In Today, said that much of the variation in iris color can be attributed to variation in the number and size of melanosomes within these melanocytes.
On the contrary, it appears that the actual number of melanocytes is relatively constant between different colored iris. Therefore, the amount and distribution of melanin contained in the melanocytes is believed to be an important determinant of eye color. The cell density of the iris stroma plays a relatively minor role in the color of iris.
The light wavelengths (Red Light, for example) easily penetrates the iris and is absorbed. However, some shorter wavelengths, especially blue light is reflected and scattered by the iris stroma. This means that with little or no iris pigment in the stroma of the iris appears blue due to reflection and scattering blue light.
Blue, green and brown
So, how these structural elements are translated into various different colors iris we see? Well, we talked a bit about what makes blue eyes.
In essence, these individuals have very few melanosomes in melanocytes stromal iris, and the resulting blue color is due to reflection and scattering of light. I must emphasize that individuals with blue eyes, not lack all pigment in their eyes that have normal melanin content in the IPE, but relatively little melanin in the iris stroma. (NOTE: People who are completely deficient in melanin have red eyes).
This condition is called albinism and is due to a genetic mutation in one of the enzymes responsible for melanin synthesis. The eyes appear red because to the unmasking 'of the blood contained in vessels of the eye in the absence of melanin.)
Brown iris the result of a high content of melanin in the iris stroma ie, a large number of melanosomes in melanocytes content. Green or hazel irises are the product of a moderate amount of melanosomes. Therefore, in a basic sense, there is a rainbow spectrum of color ranging from blue to green to brown resulting from a continuous increase in the number of melanosomes.
Change eye color
Under normal physiological conditions, exactly what might cause gradual changes in eye color beyond adolescence is not known.
Presumably, environmental and / or genetic factors may interact with cells in the iris, causing an increase or decrease in the degradation of melanin melanocytes in the stroma, and perhaps a change in the number and / or size of these melanocytes.
It is possible that stress can affect this process, but there is no evidence to support that claim in itself. I came across an interesting observation that may be relevant here. A drug called latanoprost causes increased in iris pigmentation in some patients.
This drug is a prostaglandin analogue, which means that mimics this particular hormone in the body. Exactly how this is done is unclear. But, this may provide some evidence that various hormones in the body can alter iris pigmentation over time.
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Related Resources:
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