Dictionary

miosis Contraction of the pupil. The opposite of miosis is mydriasis.

miscarriage Inadvertent loss of a pregnancy before the fetus is viable. A considerable proportion of pregnancies end in miscarriage. Also known as spontaneous abortion.

miscarriages, multiple More than one miscarriage for a woman. In multiple miscarriages, there is about a 5 percent chance that one member of the couple is carrying a chromosome translocation that is responsible for the miscarriages. Other causes of multiple miscarriage include Rh incompatibility, exposure to toxic substances that harmed the embryo, and physical problems…

missense mutation A genetic change that results in the substitution of one amino acid in protein for another. A missense mutation is responsible for sickle hemoglobin, the molecular basis of sickle cell trait and sickle cell anemia.

mite-borne typhus See typhus, scrub.

micropenis An abnormally small penis. In medical practice, the dimension of the penis that is measured is the length. The measurement is taken along the upper surface of the shaft of the penis to the tip, using a measuring tape or, preferably, a ruler. The ruler is pressed firmly into the soft tissue over the…

microphallus See micropenis.

microphthalmia An abnormally small eye. Microphthalmia is a congenital malformation of the globe, a birth defect of the eye. A related term, anophthalmia, indicates that there is no eye at all. Also known as microphthalmos.

microscope An optical instrument that augments the power of the eye to see small objects. Most optical microscopes today are compound microscopes.

microscope, compound A microscope that consists of two microscopes in series, the first serving as the ocular lens (close to the eye), and the second serving as the objective lens (close to the object to be viewed).

microscope, electron A microscope in which an electron beam replaces light to form the image. Electron microscopy (EM) has both pluses (greater magnification and resolution than optical microscopes) and minuses (the observer is not really “seeing” objects, but rather their electron densities, so artifacts may be present).

microscope, fluorescent A microscope that is equipped to examine material that fluoresces under ultraviolet (UV) light.