Morphology of the nutrient artery and its foramen in relation to femoral bone perfusion rates of laying and non-laying hens.

If arteries penetrate bones through foramina, regional artery blood flow rates can be estimated from the foramen sizes. Femoral bone blood flow rates estimated from nutrient foramen sizes were previously not absolute, but only a relative blood flow index (Q ), because the size relationship between the foramen and the occupying artery was unknown. The current study used vascular contrast and micro-computerized tomographic scanning to investigate femoral nutrient foramen and nutrient artery sizes in three groups of sub-adult chickens (non-laying hens, laying hens, and roosters) of similar ages.

Regional femoral bone blood flow rates in laying and non-laying chickens estimated with fluorescent microspheres.

The metabolic rate of vertebrate bone tissue is related to bone growth, repair and homeostasis, which are all dependent on life stage. Bone metabolic rate is difficult to measure directly, but absolute blood flow rate () should reflect local tissue oxygen requirements. A recent 'foramen technique' has derived an index of blood flow rate () by measuring nutrient foramen sizes of long bones.

Cerebral blood flow rates in recent great apes are greater than in species that had equal or larger brains.

Brain metabolic rate (MR) is linked mainly to the cost of synaptic activity, so may be a better correlate of cognitive ability than brain size alone. Among primates, the sizes of arterial foramina in recent and fossil skulls can be used to evaluate brain blood flow rate, which is proportional to brain MR. We use this approach to calculate flow rate in the internal carotid arteries , which supply most of the primate cerebrum.

Bone foramen dimensions and blood flow calculation: best practices.

Some blood vessels enter bones through foramina, leaving the size of the foramen as a gauge for estimating the rate of blood flow and hence the metabolic rate of the supplied tissues. Foramen dimensions have been measured using varied methods in previous foramen studies, to relate regional blood flows with associated physiological processes. With the increasing interests in this 'foramen technique', standard methods with minimized measurement errors are therefore required.

Blood flow rate and wall shear stress in seven major cephalic arteries of humans.

Blood flow rate ( ) in relation to arterial lumen radius (r ) is commonly modelled according to theoretical equations and paradigms, including Murray's Law ( ∝ ) and da Vinci's Rule ( ∝ ). Wall shear stress (τ) is independent of r with Murray's Law (τ ∝  ) and decreases with da Vinci's Rule (τ ∝  ). These paradigms are tested empirically with a meta-analysis of the relationships between and r in seven major arteries of the human cephalic circulation from 19 imaging studies in which both variables were presented.

Interspecific scaling of blood flow rates and arterial sizes in mammals.

This meta-study investigated the relationships between blood flow rate (; cm s), wall shear stress (τ; dyn cm) and lumen radius (; cm) in 20 named systemic arteries of nine species of mammals, ranging in mass from 23 g mice to 652 kg cows, at rest. In the dataset, derived from 50 studies, lumen radius varied between 3.7 µm in a cremaster artery of a rat and 11.

Femoral bone perfusion through the nutrient foramen during growth and locomotor development of western grey kangaroos ().

The nutrient artery passes through the nutrient foramen on the shaft of the femur and supplies more than half of the total blood flow to the bone. Assuming that the size of the nutrient foramen correlates with the size of the nutrient artery, an index of blood flow rate () can be calculated from nutrient foramen dimensions. Interspecific is proportional to locomotor activity levels in adult mammals, birds and reptiles.

Scaling of the ankle extensor muscle-tendon units and the biomechanical implications for bipedal hopping locomotion in the post-pouch kangaroo Macropus fuliginosus.

Bipedal hopping is used by macropods, including rat-kangaroos, wallabies and kangaroos (superfamily Macropodoidea). Interspecific scaling of the ankle extensor muscle-tendon units in the lower hindlimbs of these hopping bipeds shows that peak tendon stress increases disproportionately with body size. Consequently, large kangaroos store and recover more strain energy in their tendons, making hopping more efficient, but their tendons are at greater risk of rupture.