Intra-skeletal vascular density in a bipedal hopping macropod with implications for analyses of rib histology

Abstract

Human ribs are thought to be less affected by mechanical strain at the microscopic level than limb bones, implying that rib remodeling better reflects bone physiological homeostasis. Here, we test the hypothesis that rib tissue will be well vascularized and thus enhance susceptibility to metabolic influence. An intra-skeletal comparison of bone vascular canal density was conducted using a macropod animal model adapted to bipedal habitual hopping. The right humerus, ulna, radius, femur, tibia, fibula, a mid-thoracic and upper-thoracic rib of an eastern grey kangaroo (Macropus giganteus) were sectioned at the midshaft, from which histological sections were prepared. Bone vascularity from a maximum of 12 mm 2 of sub-periosteal parallel-fibred and lamellar bone was recorded, resulting in a total of 2,047 counted vessels. Vascular canal density data were corrected by cortical width, maximum length, and midshaft circumference robusticity indices computed for each bone. The fibula consistently had the highest vascular canal density, even when corrected for maximum length, cortical width and midshaft circumference robusticities. This was followed by the mid-and upperthoracic ribs. Vascularity differences between bones were relatively consistent whether vascular canal density was controlled for by cortical width or midshaft circumference robusticities. Vascular canal density and robusticity indices were also positively and negatively correlated (p < 0.05). Results confirm that the ribs are well vascularized, which facilitates bone metabolic processes such as remodeling, but the fibula also appears to be a well vascularized bone. Future research investigating human bone metabolism will benefit from examining thoracic rib or fibula samples.

Investigating super osteons in fossil Asian elephant (Elephas maximus) bone from Bangka Island, southeastern Sumatra

“…Building on this observation, we developed a research question asking whether super osteon presence differs between bone types. This could possibly occur as a result of varying mechanical capacities throughout the elephant skeleton-that is, the weight-bearing humerus compared with the largely non-weight-bearing rib and vertebrae (Stewart et al 2021).…”

Quaternary Palaeontology and Archaeology of Sumatra

“…Building on this observation, we developed a research question asking whether super osteon presence differs between bone types. This could possibly occur as a result of varying mechanical capacities throughout the elephant skeleton-that is, the weight-bearing humerus compared with the largely non-weight-bearing rib and vertebrae (Stewart et al 2021).…”

Age‐dependent change and intraskeletal variability in secondary osteons of elderly Australians

“…The current lack of research into age‐related changes to secondary osteons in bones other than the femur in the Australian population is concerning for the future development of population‐specific of age‐at‐death estimation methods, especially as it is well‐documented that different bones are under varying degrees of metabolic stress and mechanical loading which tandemly effect cortical remodelling (Eleazer & Jankauskas, 2016 ; Stewart et al., 2021 ). The femur usually experiences the greatest magnitude of biomechanical loading to support body weight in bipedal motion, and it is subjected to compression and torsional forces with movement (Pfeiffer et al., 2006 ; Ruff et al., 1993 ).…”