Length of first, twelfth, and accessory ribs in American Whites and Negroes; Their relationship to certain vertebral variations

Costal process of the first sacral vertebra: Sexual dimorphism and obstetrical adaptation

“…Sexual monomorphism in costal process length of L1 is unexpected for two reasons. First, though both the first thoracic vertebra (T1) and L1 are the leading vertebrae in their respective anatomical series (i.e., thoracic and lumbar segments), costal process length of T1 differs from that of L1 by being sexually dimorphic, with males having a longer process than females (Lanier, 1944). Second, the costal processes for the twelfth thoracic vertebra (T12; Lanier, 1944) and L2 are also sexually dimorphic, with males having a longer process than females.…”

“…First, though both the first thoracic vertebra (T1) and L1 are the leading vertebrae in their respective anatomical series (i.e., thoracic and lumbar segments), costal process length of T1 differs from that of L1 by being sexually dimorphic, with males having a longer process than females (Lanier, 1944). Second, the costal processes for the twelfth thoracic vertebra (T12; Lanier, 1944) and L2 are also sexually dimorphic, with males having a longer process than females. Moreover, the sexual monomorphism for the costal process of L1, interposed between the sexual dimorphisms for the costal processes of T12 and L2, fails to support an interpretation that the sexual monomorphism for the costal process of L5 represents a transition in dimorphism for the costal process from males being larger than females for L2 and L3, to females being larger than males for S1.…”

“…However, the ribs are sexually dimorphic. Males have longer first and twelfth ribs than females, and, more generally for ribs, males are larger than females for heights of the head and neck, anteroposterior diameter of the head, straight length from the articular facet of the tubercle to the posterior angle, and maximum and minimum diameters of the shaft (Lanier, 1944;İşcan, 1985;Dupras and Pfeiffer, 1996;Ç ölog lu et al, 1998;Owers and Pastor, 2005). This study tests the hypothesis that homologous structures (i.e., costal processes of L1 to S1) are dissimilar in their sexual dimorphism (but see O'Rahilly et al, 1990b, on whether the sacral ala is homologous with the costal processes of lumbar vertebrae).…”

“…This study tests the hypothesis that homologous structures (i.e., costal processes of L1 to S1) are dissimilar in their sexual dimorphism (but see O'Rahilly et al, 1990b, on whether the sacral ala is homologous with the costal processes of lumbar vertebrae). As males have longer ribs than females (Lanier, 1944), but as females may have a longer costal process of S1 than males (see above), this study considers whether the costal processes of L1 to L5 show a uniform difference with S1 in the direction of sexual dimorphism or a gradient of sexual dimorphism. If the lumbar vertebrae show a uniform difference with S1 in the direction of sexual dimorphism, males will have longer costal processes than females for the lumbar vertebrae, and S1 will be unique with females having a longer costal process than males.…”

An examination of the spectrum of anatomic defects and variations found in eight cases of trisomy 13

“…Dr. Donald Enlow is presently studying the sectioned skull of Case 8, which also had bilateral cleft lip and cleft palate. His analysis may elucidate some of the primary defects In a study of 1st and 12th riblengths in U.S. whites and blacks, Lanier [1944] in the development of the trisomy-13 skull. The defects are not uniform and tend, as expected, to show greater variation among themselves than would a population of normal skulls; but they have in common very broad nasal bones and a tendency for hypertelorism and platybasia.…”