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Pelvic Size (pelvic + size)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Pelvic growth: Ontogeny of size and shape sexual dimorphism in rat pelves

JOURNAL OF MORPHOLOGY, Issue 1 2007
S. Berdnikovs
Abstract The mammalian pelvis is sexually dimorphic with respect to both size and shape. Yet little is known about the differences in postnatal growth and bone remodeling that generate adult sexual dimorphism in pelvic bones. We used Sprague-Dawley laboratory rats (Rattus norvegicus), a species that exhibits gross pelvic size and shape dimorphism, as a model to quantify pelvic morphology throughout ontogeny. We employed landmark-based geometric morphometrics methodology on digitized landmarks from radiographs to test for sexual dimorphism in size and shape, and to examine differences in the rates, magnitudes, and directional patterns of shape change during growth. On the basis of statistical significance testing, the sexes became different with respect to pelvic shape by 36 days of age, earlier than the onset of size dimorphism (45 days), although visible shape differences were observed as early as at 22 days. Males achieved larger pelvic sizes by growing faster throughout ontogeny. However, the rates of shape change in the pelvis were greater in females for nearly all time intervals scrutinized. We found that trajectories of shape change were parallel in the two sexes until age of 45 days, suggesting that both sexes underwent similar bone remodeling until puberty. After 45 days, but before reproductive maturity, shape change trajectories diverged because of specific changes in the female pelvic shape, possibly due to the influence of estrogens. Pattern of male pelvic bone remodeling remained the same throughout ontogeny, suggesting that androgen effects on male pelvic morphology were constant and did not contribute to specific shape changes at puberty. These results could be used to direct additional research on the mechanisms that generate skeletal dimorphisms at different levels of biological organization. J. Morphol., 2006. © 2006 Wiley-Liss, Inc. [source]

High assimilation of the sacrum in a sample of American skeletons: Prevalence, pelvic size, and obstetrical and evolutionary implications

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009
Robert G. Tague
Abstract High assimilation sacrum is fusion of the caudal-most lumbar vertebra to the first sacral vertebra. Previous studies have shown that high assimilation is associated with clinical problems, including obstetrical difficulty. This study used adult American males (n = 1,048) and females (n = 1,038) of the Hamann,Todd and Terry skeletal collections to determine the prevalence of high assimilation and its effect on pelvic size, and to consider the obstetrical and evolutionary implications of high assimilation. The prevalence of high assimilation in this sample is 6.3%, with males and females not differing significantly from one another in their prevalence. This prevalence is near the median for that reported in 41 other samples. In both males and females, individuals with high assimilation have significantly longer anteroposterior and posterior sagittal diameters of the inlet, and shorter sacrum compared to those with a nonassimilated sacrum. Females with high assimilation have a significantly narrower sacral angulation (i.e., reduced inclination of ventral axis of sacrum), and shorter posterior sagittal diameter of the outlet compared to those with a nonassimilated sacrum. A short posterior sagittal diameter of the outlet is associated with childbirth difficulty. As high assimilation is partial homeotic transformation of a lumbar vertebra, this study supports previous research that homeotic transformation of vertebrae is selectively disadvantageous. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source]

Pelvic growth: Ontogeny of size and shape sexual dimorphism in rat pelves

JOURNAL OF MORPHOLOGY, Issue 1 2007
S. Berdnikovs
Abstract The mammalian pelvis is sexually dimorphic with respect to both size and shape. Yet little is known about the differences in postnatal growth and bone remodeling that generate adult sexual dimorphism in pelvic bones. We used Sprague-Dawley laboratory rats (Rattus norvegicus), a species that exhibits gross pelvic size and shape dimorphism, as a model to quantify pelvic morphology throughout ontogeny. We employed landmark-based geometric morphometrics methodology on digitized landmarks from radiographs to test for sexual dimorphism in size and shape, and to examine differences in the rates, magnitudes, and directional patterns of shape change during growth. On the basis of statistical significance testing, the sexes became different with respect to pelvic shape by 36 days of age, earlier than the onset of size dimorphism (45 days), although visible shape differences were observed as early as at 22 days. Males achieved larger pelvic sizes by growing faster throughout ontogeny. However, the rates of shape change in the pelvis were greater in females for nearly all time intervals scrutinized. We found that trajectories of shape change were parallel in the two sexes until age of 45 days, suggesting that both sexes underwent similar bone remodeling until puberty. After 45 days, but before reproductive maturity, shape change trajectories diverged because of specific changes in the female pelvic shape, possibly due to the influence of estrogens. Pattern of male pelvic bone remodeling remained the same throughout ontogeny, suggesting that androgen effects on male pelvic morphology were constant and did not contribute to specific shape changes at puberty. These results could be used to direct additional research on the mechanisms that generate skeletal dimorphisms at different levels of biological organization. J. Morphol., 2006. © 2006 Wiley-Liss, Inc. [source]