title: Ontogeny of 3D rib curvature and its importance for the understanding of human thorax development.
abstract: OBJECTIVE
  Sagittal and axial rib orientation relative to the spine are two factors that modify rib cage morphology during ontogeny. Some studies suggest that these factors do not operate in the same way at the upper (ribs 1-5) and lower thorax (ribs 6-10) during postnatal growth, but it is unknown if the ontogenetic thoracic changes are produced by morphological changes of the ribs (intrinsic rib factors) or by external factors related to costal joints (extrinsic rib factors).
  
  
  METHODS
  To clarify these questions, we applied 3D geometric morphometrics of landmarks and sliding semilandmarks (N = 20/rib) to 280 individual ribs (1-10) of Homo sapiens comprising the entire human ontogeny and growth simulations were carried out.
  
  
  RESULTS
  PCA shows that intrinsic rib factors (rib torsion and axial rib curvature) are ontogenetic factors of variability that contribute to configuring the adult thorax shape. Moreover, growth simulations and regression slopes suggest that the upper thorax unit is comprised by ribs 1-7 and the lower unit at least by ribs 8-10.
  
  
  CONCLUSIONS
  These results suggest anatomical constraints for ontogenetic rib variation, since ribs 1-7 (true ribs) are directly linked to the sternum. Moreover, these results are supported by functional anatomy because pulmonary kinematics would influence the upper unit and diaphragmatic kinematics would influence the lower one. Our findings are relevant not only to understanding how changes at individual ribs contribute to the adult thorax morphology, but also to the development and evolution of the modern human rib cage.
authors.affiliation: Paleoanthropology Group, Paleobiology Department, Museo Nacional de Ciencias Naturales (MNCN-CSIC), JG. Abascal 2, Madrid, 28006, Spain.|Biology Department, Faculty of Sciences, Universidad Autónoma De Madrid. Darwin 2, Madrid, 28049, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: García-Martínez
authors.affiliation: Department of Radiology, Medizinische Universität Innsbruck, 6020, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Recheis
authors.affiliation: Paleoanthropology Group, Paleobiology Department, Museo Nacional de Ciencias Naturales (MNCN-CSIC), JG. Abascal 2, Madrid, 28006, Spain.
authors.forename: Markus
authors.initials: M
authors.lastname: Bastir
mesh_terms: D000328:Adult; D000885:Anthropology, Physical; D006801:Humans; D025341:Principal Component Analysis; D012272:Ribs / Q000033:anatomy & histology* / Q000502:physiology*; D013909:Thorax / Q000033:anatomy & histology* / Q000502:physiology*
keywords: development; geometric morphometrics; individual ribs; ontogeny; rib cage