Number of veebrae is usually constant in

Ans. a. Cervical Author please provideIllustrated Encyclopedia of Human Anatomic Variation: Opus V: Skeletal Systems: Veebral column; Numerical Variation in Veebral Column by Ronald A. Bergman, PhD; Adel K. Afifi, MD, MS; Ryosuke Miyauchi, MD.The usual grouping formula of 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal veebrae is found in only aboutThe cervical region is repoed to be the most constantQ, the coccygeal the most variable20% of individuals studied.The number of elements of the veebral column has been repoed to vary between 32 and 35. Addition to a group is frequently seen, which occurs through the reduction in number of veebrae of an adjacent group, the total number beingThe location of such a veebra is predominately at the ends of the column and at the levels of transition between its regions. Thus, sacralization of the fifth lumbar, lumbar-like aicular processes in the eleventh thoracic, and thoracic costal facets on the seventh cervical are observed.unchanged. In this variation, the veebra added is usually intermediate in form between the adjacent groups.The levels of transition may be shifted cephalad, resulting in 23 mobile veebrae, or shifted caudad, resulting in 25 presacral veebrae. Such variations may occur in 2-11% of the populationThe number of veebrae comprising the sacrum maybe increased to six, resulting from the fusion of the first coccygeal (50% in whites, 30% in Negroes) or, less often, of the last lumbar (sacralization) (8% in whites, 11% in Negroes); or it maybe increased to seven, resulting from the fusion of the first coccygeal and the last lumbar (4% in whites, 1.5% in Negroes). The number maybe reduced to four, apparently by the lumbarization of the first sacral (0.4% in whites, 1.5% in Negroes).Number of veebraeMost constant: Cervical regiondegMost variable: coccygeal regiondeg