Abstract
Reindeer (Rangifer tarandus) have evolved elaborate nasal turbinate structures that are perfused via a complex vascular
network. These are subject to thermoregulatory control, shifting between heat conservation and dissipation, according to
the animal’s needs. The three-dimensional design of the turbinate structures is essential in the sense that they determine the
efciency with which heat and water are transferred between the structure and the respired air. The turbinates have already
a relatively large surface area at birth, but the structures have yet not reached the complexity of the mature animal. The aim
of this study was to elucidate the structure–function relationship of the heat exchange process. We have used morphometric
and physiological data from newborn reindeer calves to construct a thermodynamic model for respiratory heat and water
exchange and present novel results for the simulated respiratory energy losses of calves in the cold. While the mature reindeer
efectively conserves heat and water through nasal counter-current heat exchange, the nose of the calf has not yet attained a
similar efciency. We speculate that this is probably related to structure-size limitations and more favourable climate conditions during early life. The fully developed structure–function relationship may serve as inspiration for engineering design.
Simulations of diferent extents of mucosal vascularization suggest that the abundance and pattern of perfusion of veins in
the reindeer nasal mucosa may contribute to the control of temperature profles, such that nasal cavity tissue is sufciently
warm, but not excessively so, keeping heat dissipation within limits.
network. These are subject to thermoregulatory control, shifting between heat conservation and dissipation, according to
the animal’s needs. The three-dimensional design of the turbinate structures is essential in the sense that they determine the
efciency with which heat and water are transferred between the structure and the respired air. The turbinates have already
a relatively large surface area at birth, but the structures have yet not reached the complexity of the mature animal. The aim
of this study was to elucidate the structure–function relationship of the heat exchange process. We have used morphometric
and physiological data from newborn reindeer calves to construct a thermodynamic model for respiratory heat and water
exchange and present novel results for the simulated respiratory energy losses of calves in the cold. While the mature reindeer
efectively conserves heat and water through nasal counter-current heat exchange, the nose of the calf has not yet attained a
similar efciency. We speculate that this is probably related to structure-size limitations and more favourable climate conditions during early life. The fully developed structure–function relationship may serve as inspiration for engineering design.
Simulations of diferent extents of mucosal vascularization suggest that the abundance and pattern of perfusion of veins in
the reindeer nasal mucosa may contribute to the control of temperature profles, such that nasal cavity tissue is sufciently
warm, but not excessively so, keeping heat dissipation within limits.
