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 ?
Concha aovada, delgada y translucida, algo comprimida, subequilateral, lado anterior mas alargado con borde ampliamente redondeado; lado posterior corto, deprimido, con borde redondeado, y las valvas flexionadas hacia la derecha; charnela con dos dientes cardinales en cada valva y el ligamento hundido casi alcanza el borde de la lamina articular bajo y detras de los picos; escultura consiste en estrias conmarginales muy finas, que estan interrumpidas por algunas lineas de crecimiento ampliamente separadas; color externo blanco mate con manchas amarillentas, interior blanco brillante con tonalidad amarillenta en la cavidad umbonal; seno paleal amplio, anguloso dorsalmente y con extremo redondeado, bordes de las valvas lisos.
Medium-sized, slightly prosocline suborbicular Aviculopecten; auricular sinuses moderately deep; body costae on left valve narrow, varying in size with one to three smaller costae between larger ones, increasing by intercalation; interfaces narrow; anterior auricle with 20-22 fine costae, posterior auricle with 15 fine costae; 62 body costae at distance of 25 mm from hinge line; numerous closely-spaced, comarginal growth lamellae; right valve with nearly equal-sized body costae separated by equal or narrower interspaces; anterior auricle with eight costae, posterior auricle with 19-20 finer costae; 87 body costae at a distance of 20 mm from hinge line; umbonal angle of 55 degrees; fine comarginal growth lines.
Concha alargada, estrecha y arqueada, con el borde ventral comprimido, lo cual origina un fuerte lomo umbonal, el pico es terminal y el borde dorsal mas arqueado hacia la parte posterior; charnela con dos o tres dientes debiles; el resilio es casi tan largo como el margen dorsal posterior.
Sulcus deep and narrow, with steep lateral slopes, originating at the umbonal area and terminating with a trapezoidal tongue occupying about 40% of maximum shell width.
The Iranian shells show a finely pitted surface of the larval and adult shell, a moderately convex sagittal profile more strongly curved in the umbonal area in the dorsal valve, whereas a single ventral valve shows a submarginal umbo.
Fifteen days after fertilization, we divided larvae into two groups based on their developmental stage (umbonal or pediveliger) and recorded survival, size, and developmental stage of individuals over the next 4 months.
Each larva was also staged (D-stage or umbonal) to determine if its size was within the range for a M.
Choi and Chang (2003) extended the evaluation to the more advanced larval developmental stages in the pearl oyster Pinctadafucata martensii and discovered that prior to the umbonal stage, postthaw survival rates increased as the larvae developed, with the best survival rate being as high as 91% at late D-larval stage, followed by a decrease in survival with age.
The following shell characteristics were recorded: shell morphology, shell wall rigidity or thickness, valve lamellae, radial ribs, shell color, ligament channel, umbonal cavity volume, interior shell color, adductor muscle scar color and shape.
They have a very small anterior adductor scar, a continuous posterior byssus retractor scar and an anterior retractor scar that is situated in the posterior part of the umbonal cavity behind the beaks.