In anatomy, heterochromia refers to a difference in coloration, usually of the iris but also of hair or skin. Heterochromia is a result of the relative excess or lack of melanin (a pigment). It may be inherited, due to genetic mosaicism, or due to disease or injury. Eye color, specifically the color of the irises, is determined primarily by the concentration and distribution of melanin. The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic). In humans, usually, an excess of melanin indicates hyperplasia of the iris tissues, whereas a lack of melanin indicates hypoplasia. Heterochromia of the eye (heterochromia iridis or heterochromia iridum) is of two kinds. In complete heterochromia, one iris is a different color from the other. In partial heterochromia or sectoral heterochromia, part of one iris is a different color from its remainder. Partial or sectoral heterochromia is much less common than complete heterochromia and is typically found in autosomally inherited disorders such as Hirschsprung's disease and Waardenburg syndrome. seifuku:
Japan introduced school uniforms in the late 19th century. Today, school uniforms are almost universal in the Japanese public and private school systems. They are also used in some women's colleges. The Japanese word for uniform is seifuku (制服?).
In the majority of elementary schools, students are not required to wear a uniform to school. Where uniforms are required, many boys wear white shirts, short pants, and caps. Young boys often dress more formally in their class pictures than they do other days of the school year. Girls' uniforms might include a gray pleated skirt and white blouse. Occasionally the sailor outfit is used for girls. The uniform codes may vary by season to work with the environment and occasion. It is common for both boys and girls to wear brightly colored caps to prevent traffic accidents. Also, it is normal for uniforms to be worn outside of school areas. This is going out of fashion and many students are wearing casual dress.
The Japanese junior- and senior-high-school uniform traditionally consists of a military style uniform for boys and a sailor outfit for girls. These uniforms are based on Meiji era formal military dress, themselves modeled on European-style naval uniforms. The sailor outfit replace the undivided hakama (andon bakama 行灯袴) designed by Utako Shimoda between 1920–30. While this style of uniform is still in use, many schools have moved to more Western-pattern parochial school uniform styles. These uniforms consist of a white shirt, tie, blazer with school crest, and tailored trousers (often not of the same color as the blazer) for boys and a white blouse, tie, blazer with school crest, and tartan culottes or skirt for girls.
Regardless of what type of uniform any particular school assigns its students, all schools have a summer version of the uniform (usually consisting of just a white dress shirt and the uniform slacks for boys and a reduced-weight traditional uniform or blouse and tartan skirt with tie for girls) and a sports-activity uniform (a polyester track suit for year-round use and a t-shirt and short pants for summer activities). Depending on the discipline level of any particular school, students may often wear different seasonal and activity uniforms within the same classroom during the day. Individual students may attempt to subvert the system of uniforms by wearing their uniforms incorrectly or by adding prohibited elements such as large loose socks or badges. Girls may shorten their skirts; boys may wear trousers about the hips, omit ties, or keep their shirts unbuttoned.
Since some schools do not have sex-segregated changing- or locker-rooms, students may change for sporting activities in their classrooms. As a result, such students may wear their sports uniforms under their classroom uniforms. Certain schools also regulate student hairstyles, footwear, and book bags; but these particular rules are usually adhered to only on special occasions, such as trimester opening and closing ceremonies and school photo days.