Ontogenetic and regional morphologic variations in the turkey ulna diaphysis: Implications for functional adaptation of cortical bone
Article first published online: 28 MAY 2003
Copyright © 2003 Wiley-Liss, Inc.
The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology
Volume 273A, Issue 1, pages 609–629, July 2003
How to Cite
Skedros, J. G., Hunt, K. J., Hughes, P. E. and Winet, H. (2003), Ontogenetic and regional morphologic variations in the turkey ulna diaphysis: Implications for functional adaptation of cortical bone. Anat. Rec., 273A: 609–629. doi: 10.1002/ar.a.10073
- Issue published online: 28 MAY 2003
- Article first published online: 28 MAY 2003
- Manuscript Accepted: 12 MAR 2003
- Manuscript Received: 28 JAN 2003
- bone adaptation;
- turkey ulna;
- collagen fiber orientation;
- osteocyte lacunae;
This study examines relationships between bone morphology and mechanically mediated strain/fluid-flow patterns in an avian species. Using mid-diaphyseal transverse sections of domestic turkey ulnae (from 11 subadults and 11 adults), we quantified developmental changes in predominant collagen fiber orientation (CFO), mineral content (%ash), and microstructure in cortical octants or quadrants (i.e., %ash). Geometric parameters were examined using whole mid-diaphyseal cross-sections. The ulna undergoes habitual bending and torsion, and demonstrates nonuniform matrix fluid-flow patterns, and high circumferential strain gradients along the neutral axis (cranial-caudal) region at mid-diaphysis. The current results showed significant porosity differences: 1) greater osteocyte lacuna densities (N.Lac/Ar) (i.e., “non-vascular porosity”) in the caudal and cranial cortices in both groups, 2) greater N.Lac/Ar in the pericortex vs. endocortex in mature bones, and 3) greater nonlacunar porosity (i.e., “vascular porosity”) in the endocortex vs. pericortex in mature bones. Vascular and nonvascular porosities were not correlated. There were no secondary osteons in subadults. In adults, the highest secondary osteon population densities and lowest %ash occurred in the ventral-caudal, caudal, and cranial cortices, where shear strains, circumferential strain gradients, and fluid displacements are highest. Changes in thickness of the caudal cortex explained the largest proportion of the age-related increase in cranial-caudal breadth; the thickness of other cortices (dorsal, ventral, and cranial) exhibited smaller changes. Only subadult bones exhibited CFO patterns corresponding to habitual tension (ventral) and compression (dorsal). These CFO variations may be adaptations for differential mechanical requirements in “strain-mode-specific” loading. The more uniform oblique-to-transverse CFO patterns in adult bones may represent adaptations for shear strains produced by torsional loading, which is presumably more prevalent in adults. The micro- and ultrastructural heterogeneities may influence strain and fluid-flow dynamics, which are considered proximate signals in bone adaptation. Anat Rec Part A 273A:609–629, 2003. © 2003 Wiley-Liss, Inc.