Author: Glossary
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Uveal pigment
Melanin in the choroid layer of the eye, the ciliary processes, and the posterior surface of the iris. Uveal pigment absorbs light within the eyeball to prevent glare.
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Hematogenous pigment
A pigment from hemoglobin of the erythrocytes.
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Exogenous pigment
A pigment produced outside the human body.
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Endogenous pigment
A pigment produced within the human body, as melanin.
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Blood pigment
A pigment in blood (hemo globin) or a derivative of it (hematin, hemin, methemoglobin, hemosiderin).
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Piezoelectricity
Production of an electric current by application of pressure to certain crystals such as mica, quartz, or Rochelle salt.
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Piezoelectric effect
In ultrasound, a change of the mechanical action of ceramic crystals into an electrical impulse and vice versa. Discovered by the Curies in 1880, this phenomenon involves the deformation of a crystal when a voltage is applied across its faces. The application of charge induces the crystal to undergo deformation, and upon removing the charge,…
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Piesimeter
A device for measurement of the skin’s sensitivity to pressure.
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Pierce
To penetrate body tissue, usually in order to place an ornamental ring or stud on the surface of he skin.
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Pictograph
A set of test pictures used for testing vision in children and illiterate adults.