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Linea nigra

Noun 1. A dark vertical line that appears on the abdomen during about three quarters of all pregnancies. The brownish streak is usually about a centimeter in width. The line runs vertically along the midline of the abdomen from the pubis to the umbilicus, but can also run from the pubis to the top of the abdomen. Linea nigra is due to increased melanocyte-stimulating hormone made by the placenta, which also causes melasma and darkened nipples. Fair-skinned women show this phenomenon less often than women with darker pigmentation. ( 2. A dark vertical line running up the abdomen from the pubis to the navel that forms during pregnancy. ( 3. A long narrow dark streak running along the midline of the abdomen, from the umbilicus to the pubis. ( 4. Linea alba that is hyperpigmented temporarily during pregnancy. ( Word origin: Latin for “black...

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Noun, pl. linguae 1. A tongue. ( 2. A median process of the labium, at the underside of the mouth in insects, and serving as a tongue. ( 3. A mobile mass of muscular tissue covered with mucous membrane and located in the oral cavity. ( Syn: tongue, glossa, clapper Word origin: Latin word for...

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Noun 1. Any of several tongue-shaped bony structures, especially that which forms the anterior border of the mandibular foramen. ( Lingula of left lung Sphenoidal lingula Lingula of mandible Lingula of cerebellum 2. (Genus) A brachiopod genus of the family Lingulidae, which is among the few brachiopods surviving today but also known from fossils over 500 million years old. ( Word origin: Diminutive of Latin lingua, hence, a little...

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Lissauer’s tract

Noun 1. A small strand situated in relation to the tip of the posterior column close to the entrance of the posterior nerve roots. ( 2. A slender column of white matter between the dorsal gray column and the periphery of the spinal cord. ( Syn: fasciculus of Lissauer, tract of Lissauer, dorsolateral fasciculus, dorsolateral tract, zone of Lissauer, posterolateral...

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Noun Literally means smooth brain. 1. A rare brain formation disorder caused by defective neuronal migration during the 12th to 24th weeks of gestation resulting in a lack of development of brain folds (gyri) and grooves (sulci). It is a form of cephalic disorder. Terms such as ‘agyria’ (no gyri) or ‘pachygyria’ (broad gyri) are used to describe the appearance of the surface of the brain. ( 2. A disorder characterized by smoothness (lack of folds and grooves) of the brain. ( 3. Condition in which the brain is smooth owing to failure of development of cerebral gyri. ( Word origin: From Greek lissos,...

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