umbo

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umbo

 [um´bo] (L.)
1. a rounded elevation.
2. the slight projection at the center of the outer surface of the tympanic membrane.

um·bo

, gen.

um·bo·nis

, pl.

um·bo·nes

(ŭm'bō, -bō-nis, -bō-nēs),
1. A projecting point of a surface.
2. Umbo of tympanic membrane.
[L. boss of a shield, a knob]

umbo

(ŭm′bō)
n. pl. umbos or umbones (ŭm-bō′nēz)
A small anatomical projection on a surface, such as that on the inner surface of the eardrum at the end of the manubrium of the malleus, corresponding to the most elevated point of the eardrum.

um′bo·nal (ŭm′bə-nəl, ŭm-bō′nəl), um·bon′ic (ŭm-bŏn′ĭk) adj.

um·bo

, pl. umbones (ŭm'bō, -nēz) [TA]
1. A projecting point of a surface.
2. [TA]
Synonym(s): umbo of tympanic membrane.
[L. boss of a shield, a knob]

umbo

the pointed centre of a clam shell, being the oldest part around which are many concentric lines of growth.

umbo 

An area (0.15 mm-0.20 mm) in the centre of the foveola. Stimulation of this area results in the highest visual acuity.
References in periodicals archive ?
Stenzel (1971) description of Saccostrea included "all non-incubatory oysters which have cho-mata on the margins of the shells and a distinct pallial impression of separate small muscles, constituting a disjunct pallial line," to which Dinamani (1976) added, "the distinctive features of the prodisso-conch such as orthogyrate umbones and symmetrical teeth." Thus, the results of this study support S.
valdensis which has a more elongated shape, the umbones of M.
siliqua is active and uniquely adapted for horizontal movement by virtue of a disproportionately large anterior region (i.e., anterior to the umbones).
They have terminal umbones, a rather narrow anterior margin and a broad posterior part that give the valves a wedge-shaped outline.