Friday, May 19, 2006

pupil

Quick Definition: 학생; 안구의 동공
pupil1 (pyū'pəl) pronunciation
n.
  1. A student under the direct supervision of a teacher or professor.
  2. Law. A minor under the supervision of a guardian.

[Middle English pupille, orphan, from Old French, from Latin pūpillus, diminutive of pūpus, boy.]


pupil2 (pyū'pəl) pronunciation
n.

The apparently black circular opening in the center of the iris of the eye, through which light passes to the retina.

[Middle English, from Old French pupille, from Latin pūpilla, little doll, pupil of the eye (from the tiny image reflected in it). See pupil1.]

pu'pilar adj.







pupil

noun

    One who is being educated: learner, scholar, student. See teach/learn.







pupil
n

Definition: person who is just learning something
Antonyms: professor, teacher








pupil

The seemingly black, central opening in the iris of the eye, through which light enters.







pupil (pyū'pəl)
n.

The apparently black circular opening in the center of the iris of the eye, through which light passes to the retina.

pu'pilar adj.






Note: click on a word meaning below to see its connections and related words.

The noun pupil has 3 meanings:

Meaning #1: a learner who is enrolled in an educational institution
Synonyms: student, educatee

Meaning #2: contractile aperture in the iris of the eye

Meaning #3: a child attending school
Synonym: schoolchild








pupil
The human eyeThe pupil is the central transparent area (showing as black). The greenish-brown area surrounding it is the iris. The white outer area is the sclera, the central transparent part of which is the cornea.
Enlarge
The human eye
The pupil is the central transparent area (showing as black). The greenish-brown area surrounding it is the iris. The white outer area is the sclera, the central transparent part of which is the cornea.
Close up of a cat pupil.
Enlarge
Close up of a cat pupil.

In the eye, the pupil is the opening in the middle of the iris. It appears black because most of the light entering it is absorbed by the tissues inside the eye. In humans and many animals (but few fish), the size of the pupil is controlled by involuntary contraction and dilation of the iris, in order to regulate the intensity of light entering the eye. This is known as the pupillary reflex. In bright light, the human pupil has a diameter of about 1.5 millimeter, in dim light the diameter is enlarged to about 8 millimeter.

The shape of the pupil varies between species. Common shapes are circular or slit-shaped, although more convoluted shapes can be found in aquatic species. The reasons for the variation in shapes are complex; the shape is closely related to the optical characteristics of the lens, the shape and sensitivity of the retina, and the visual requirements of the species.

Slit-shaped pupils are found in species which are active in a wide range of light levels. In strong light, the pupil constricts and is small, but still allows light to be cast over a large part of the retina.

The orientation of the slit may be related to the direction of motions the eye is required to notice most sensitively (so a vertical pupil would increase the sensitivity of the eyes of a small cat to the horizontal scurrying of mice).

In snakes, slit-shaped pupils are associated with venomous species, while non-venomous snakes have round pupils.

When an eye is photographed with a flash, the iris cannot close the pupil fast enough and the blood-rich retina is illuminated, resulting in the red-eye effect.

Dilation of the pupil

Dilation occurs when signals from sympathetic fibers (these fibres travel from the sympathetic trunk up to the face) cause the iris dilator muscles to contract. Damage to the sympathetic tract to the face (cranial nerve VII) results in Horner's syndrome, a symptom of which is excessive pupillary constriction (miosis) in one eye. This disparity in pupil size is termed anisocoria.

The human pupil dilates if the person sees something (or someone) of interest or is aroused. Studies have shown that humans (especially females) are judged as more attractive if their pupils are wide open and more dilated than normal. The name Belladonna (beautiful lady) comes from the fabled use of the juices of the Nightshade plant by Italian women who would use eyedrops made from an extract of the plant in their eyes in order to enlarge their pupils and make their eyes appear more beautiful. In some cases gradual blindness has occurred through the overuse and abuse of belladonna to enhance the beauty of the eyes. Atropine, a chemical found in belladonna, is used by modern eye doctors to dilate the pupils so that they can examine the retina. Excessive dilation is called mydriasis.

Hallucinogenic drugs, such as LSD and psilocybin, and some stimulants such as cocaine also cause dilation of the pupils.

Constriction of the pupil

When bright light is shone on the eye, it will automatically constrict. This is the pupillary reflex, which protects the retina from bright light, and is an important test of brainstem function. Also, the pupil will constrict if a person sees a thing or person which arouses anger or loathing.

The oculomotor nerve, specifically the parasympathetic part coming from the Edinger-Westphal nucleus, terminates on the circular iris sphincter muscle. When this muscle contracts, it reduces the size of the pupil.

Certain drugs cause constriction of the pupils, such as heroin.

Another term for the constriction of the pupil is miosis. Substances that cause miosis are called miotic.

See also







Translations for: Pupil

Nederlands (Dutch)
pupil, leerling(e), scholier

Franais (French)
lve, pupille

Deutsch (German)
n. - Schler
n. - Pupille

ή (Greek)
n. ή, (.) ό (ύ)

Italiano (Italian)
pupilla, pupillo, alunno, allievo

Portugus (Portuguese)
n. - aluno (m)

Русский (Russian)
зрачок, подопечный, ученик

Espaol (Spanish)
n. - pupila, pupilo, alumno
n. - pupila

Svenska (Swedish)
n. - elev, lrjunge, myndling (jur.)

中国话 (Simplified Chinese)
n. - 小学生, 学生, 未成年人, 被监护人, 弟子
n. - 瞳孔

中國話 (Traditional Chinese)
n. - 瞳孔
n. - 小學生, 學生, 未成年人, 被監護人, 弟子

日本語 (Japanese)
n. - 生徒, 弟子, 門下生, 瞳, 瞳孔, 被後見人

العربيه (Arabic)
(الاسم) تلميذ, بؤبؤ العين

עברית (Hebrew)‬
n. - ‮תלמיד, עורך-דין מתמחה, קטין הנמצא בהשגחת אפיטרופוס‬
n. - ‮אישון העין‬






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Some good pupil pages on the web:


American Sign Language
commtechlab.msu.edu




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