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Medical Dictionary - Dictionary of Medicine and Human Biology


Medical Dictionary


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microcytosis (mi′kro-si-to′sis)
SYN: microcythemia. [microcyte + G. -osis, condition]

microdactylia (mi′kro-dak-til′e-a)
SYN: microdactyly.

microdactylous (mi-kro-dak′ti-lus)
Relating to or characterized by microdactyly.

microdactyly (mi-kro-dak′ti-le)
Smallness or shortness of the fingers or toes. SYN: microdactylia. [micro- + G. dactylos, finger, toe]

microdialysis
A method of studying extracellular fluid composition and response to exogenous agents, utilizing a tiny tubular probe with a dialysis membrane and fluid flow rates of 1–3 μL/min, inserted into tissues.

microdissection (mi′kro-di-sek′shun)
Dissection of tissues under a microscope or magnifying glass, usually done by teasing the tissues apart by means of needles.

microdont (mi′kro-dont)
Having small teeth; denoting a skull with a dental index below 41.9. [micro- + G. odous (odont-), tooth]

microdontia, microdontism (mi-kro-don′she-a, -don′tizm)
A condition in which a single tooth, or pairs of teeth, or the whole dentition, may be disproportionately small. [micro- + G. odous, tooth]

microdose (mi′kro-dos)
A very small dose.

microdrepanocytosis (mi′kro-drep′a-no-si-to′sis)
A chronic hemolytic anemia resulting from interaction of the genes for sickle cell anemia and thalassemia. [microcytosis + drepanocytosis]

microdysgenesia (mi′kro-dis-ge-ne′se-a)
Increase in partially distopic neurons in the stratum zonale, white matter, hippocampus and cerebellar cortex, producing an indistinct border between cortex and subcortical white matter and a columnar arrangement of cortical neurons; seen in patients with primary generalized epilepsy. [micro- + dys- + G. genesis, production]

microelectrode (mi′kro-e-lek′trod)
An electrode of very fine caliber consisting usually of a fine wire or a glass tube of capillary diameter (10 μm to 1 mm) drawn to a fine point and filled with saline or a metal such as gallium or indium (while melted); used in physiologic experiments to stimulate or to record action currents of extracellular or intracellular origin.

microelements (mi′kro-el′e-ments)
SYN: trace elements, under element.

microencephaly (mi′kro-en-sef′a-le)
SYN: micrencephaly.

microerythrocyte (mi′kro-e-rith′ro-sit)
SYN: microcyte.

microevolution (mi′kro-ev-o-loo′shun)
The evolution of bacteria and other microorganisms through mutations.

microfibril (mi-kro-fi′bril)
A very small fibril having an average diameter of 13 nm; it may be a bundle of still smaller elements, the microfilaments.

microfilament (mi-kro-fil′a-ment)
The finest filamentous element of the cytoskeleton, having a diameter of about 5 nm and consisting primarily of actin. SEE ALSO: actin filament.

microfilaremia (mi′kro-fil-a-re′me-a)
Infection of the blood with microfilariae. M. caused by Wuchereria bancrofti is characterized by sharp nocturnal periodicity, apparently tied to the nocturnal habits of the vector mosquitoes; in geographic areas where mosquitoes are not strictly night-biters (as in parts of Polynesia), the microfilarial periodicity is modified or absent. SEE ALSO: periodic filariasis.

microfilaria, pl .microfilariae (mi′kro-fi-lar′e-a, -e)
Term for embryos of filarial nematodes in the family Onchocercidae. In the past this term has been used as a generic designation ( e.g., M. bancrofti, M. malaya). See Filaria.

microfilm (mi′kro-film)
1. A photographic film bearing greatly reduced images of printed records. 2. To record on m..

microflora (mi′kro-flo-ra)
The bacteria and fungi that inhabit an area.

microgamete (mi-kro-gam′et)
The male element in anisogamy, or conjugation of cells of unequal size; it is the smaller of the two cells and actively motile. [micro- + G. gametes, husband]

microgametocyte (mi-kro-gam′e-to-sit)
The mother cell producing the microgametes, or male elements of sexual reproduction in sporozoan protozoans and fungi. SYN: microgamont.

microgamont (mi-kro-gam′ont)
SYN: microgametocyte.

microgamy (mi-krog′a-me)
Conjugation between two young cells, the recent product of sporulation or some other form of reproduction. [micro- + G. gamos, marriage]

microgastria (mi-kro-gas′tre-a)
Smallness of the stomach. [micro- + G. gaster, stomach]

microgenia (mi-kro-jen′e-a)
Abnormal smallness of the chin resulting from the underdevelopment of the mental symphysis. [micro- + G. geneion, chin]

microgenitalism (mi-kro-jen′i-tal-izm)
Abnormal smallness of the external genital organs.

microglia (mi-krog′le-a)
Small neuroglial cells, possibly of mesodermal origin, which may become phagocytic, in areas of neural damage or inflammation. SYN: Hortega cells, m. cells, microglial cells. [micro- + G. glia, glue]

microgliacyte (mi-krog′le-a-sit)
A cell, especially an embryonic cell, of the microglia. [micro- + G. glia, glue, + kytos, cell]

microglioma (mi-krog′le-o′ma)
Obsolete term for an intracranial neoplasm of microglial cell origin that is structurally similar to lymphoma. [microglia + G. -oma, tumor]

microgliomatosis (mi′kro-gle-o-ma-to′sis)
Obsolete term for a condition characterized by the presence of multiple microgliomas.

microgliosis (mi-krog′le-o′sis)
Presence of microglia in nervous tissue secondary to injury. [microglia + G. -osis, condition]

microglobulin (mi′kro-glob′oo-lin)
1. Any serum or urinary globulin of molecular mass below about 40 kd, including especially Bence Jones proteins, under protein. 2. On occasions, a term used to refer to 7S immunoglobins ( e.g., IgG). β-m. a polypeptide of 11,600 Da that forms the light chain of class 1 major histocompatibility antigens and can therefore be detected on all cells bearing these antigens. Free β-m. is found in the blood and urine of patients with certain diseases, including Wilson disease, cadmium poisoning, and renal tubular acidosis. β2-m. the light chain of the histocompatibility class I molecule. This chain is invariant within a given species; found in elevated levels in individuals with Wilson disease and in alcohol-induced liver cirrhosis.

microglossia (mi-kro-glos′e-a)
Smallness of the tongue. [micro- + G. glossa, tongue]

micrognathia (mi-kro-na′the-a, mi-krog-nath′e-a)
Abnormal smallness of the jaws, especially of the mandible. [micro- + G. gnathos, jaw] m. with peromelia hypoplasia of the mandible with malformed and missing teeth, birdlike face, and severe deformities of the hands and forearms and sometimes of feet and legs. SYN: Hanhart syndrome.

microgram (μg, γ) (mi′kro-gram)
One-millionth of a gram.

micrograph (mi′kro-graf)
1. An instrument that magnifies the microscopic movements of a diaphragm by means of light interference and records them on a moving photographic film; may be used for recording various pulse curves, sound waves, and any forms of motion that may be communicated through the air to a diaphragm. 2. SYN: photomicrograph. [micro- + G. grapho, to write] electron m. the image produced by the electron beam of an electron microscope, recorded on an electron-sensitive plate or film. light m. a photograph produced by means of a light microscope.

micrography (mi-krog′ra-fe)
1. Writing with very minute letters, sometimes observed in psychoses and in paralysis agitans. 2. A description of objects seen with a microscope. 3. SYN: photomicrography. [micro- + G. grapho, to write]

microgyria (mi-kro-ji′re-a)
Abnormal narrowness of the cerebral convolutions. [micro- + G. gyros, convolution]

microhepatia (mi-kro-he-pat′e-a)
Abnormal smallness of the liver. [micro- + G. hepar (hepat-), liver]

microheterogeneity (mi′kro-het′er-o-je-ne′i-te;ne′i-te)
Slight differences in structure between essentially identical molecules; E.G., in the saccharide portion of a glycoprotein.

microhm (μΩ) (mi′krom)
One-millionth of an ohm. SYN: micro-ohm.

microincineration (mi′kro-in-sin′e-ra′shun)
Combustion, in a furnace, of organic constituents in a tissue section so that the remaining mineral ash can be examined microscopically. SYN: spodography.

microincision (mi-kro-in-sizh′un)
An incision made with the aid of a microscope.

microinjector (mi′kro-in-jek-tor)
An instrument for infusion of very small amounts of fluids or drugs into animals or humans.

microinvasion (mi′kro-in-va′zhun)
Invasion of tissue immediately adjacent to a carcinoma in situ, the earliest stage of malignant neoplastic invasion.

microkatal (mi′kro-kat′al)
One-millionth of a katal.

microkymatotherapy (mi′kro-ki-mat′o-thar′a-pe)
Treatment with high frequency radiations of 3,000,000,000 Hz (3000 MHz), at a wavelength of 10 cm. SYN: microwave therapy. [micro- + G. kyma, a wave, + therapeia, treatment]

microleukoblast (mi-kro-loo′ko-blast)
SYN: micromyeloblast.

microliter (μl, μL) (mi′kro-le-ter)
One-millionth of a liter.

microlith (mi′kro-lith)
A minute calculus, usually multiple, sometimes constituting a coarse sand called gravel. [micro- + G. lithos, stone]

microlithiasis (mi-kro-li-thi′a-sis)
The formation, presence, or discharge of minute concretions, or gravel, e.g., testicular m.. pulmonary alveolar m. microscopic granules of calcium or bone disseminated throughout the lungs.

micrology (mi-krol′o-je)
The science concerned with microscopic objects, of which histology is a branch. [micro- + G. logos, study]

micromanipulation (mi′kro-ma-nip′u-la′shun)
Dissection, teasing, stimulation, etc., under the microscope, of minute structures; e.g., tissue cells or unicellular organisms.

micromanipulator (mi′kro-ma-nip′u-la′ter, -tor)
An instrument used in micromanipulation, whereby microdissection, microinjection, and other maneuvers are performed, usually with the aid of a microscope.

micromazia (mi-kro-ma′ze-a)
Condition in which the breasts are rudimentary and functionless. [micro- + G. mazos, breast]

micromelia (mi-kro-me′le-a)
Condition of having disproportionately short or small limbs. SEE ALSO: achondroplasia. SYN: nanomelia. [micro- + G. melos, limb]

micromere (mi′kro-mer)
A blastomere of small size; for example, one of the blastomeres at the animal pole of an amphibian egg. [micro- + G. meros, a part]

micromerozoite (mi′kro-mer-o-zo′it)
A small merozoite.

micrometastasis (mi′kro-me-tas′ta-sis)
A stage of metastasis when the secondary tumors are too small to be clinically detected, as in micrometastatic disease.

micrometastatic (mi′kro-met-a-stat′ik)
Denoting or characterized by micrometastasis, as in m. disease.

micrometer (μm) (mi-krom′e-ter)
1. One-millionth of a meter; formerly called micron. 2. A device for measuring various types of objects in an accurate and precise manner; in medicine and biology, the term is usually used with reference to a glass slide or lens that is accurately marked for measuring microscopic forms. [micro- + G. metron, measure] caliper m. a gauge with a calibrated m. screw for the measurement of thin objects such as microscope cover glasses and slides. filar m. an ocular m. with a line moved by a ruled drum such that a movement of the line of 5 μm or less may be made in relation to fixed parallel lines. ocular m. a glass disk that fits in a microscope eyepiece and that has a ruled scale; when calibrated with a slide m., direct measurements of a microscopic object can be made. slide m. a scale made on a microscope slide with lines ruled in divisions, usually, of 0.01 mm; typically used to calibrate an ocular m..

micrometry (mi-krom′e-tre)
Measurement of objects with some type of micrometer and a microscope.

micromicro- (μμ)
Prefix formerly used to signify one-trillionth (10−12); now pico-.

micromicrogram (μμg) (mi′kro-mi′kro-gram)
Former term for picogram.

micromicron (μμ) (mi-kro-mi′kron)
Former term for picometer.

microminerals (mi-kro-min′er-alz)
SYN: trace elements, under element.

micromolar (μmol/L) (mi-kro-mo′lar)
Denoting a concentration of 10−6 mol/L.

micromole (μmol) (mi′kro-mol)
One-millionth of a mole.




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