AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 5 617-R623, Copyright © 1985 by American Physiological Society
Vascular basis for regulation of nasal heat exchange in reindeer
H. K. Johnsen, A. S. Blix, L. Jorgensen and J. B. Mercer
A hypothesis for the operation and control of nasal heat exchange in
reindeer is presented that originated from studies of the nasal vascular
anatomy and has been supported by physiological measurements as well as
test experiments on a physical prototype model of the reindeer nose. A
central theme of our hypothesis is that the nasal mucosa possesses arterial
and venous retia that communicate by way of capillaries and arteriovenous
anastomoses. During heat conservation the blood runs countercurrent in
these retia, whereby a temperature gradient along the nasal mucosa can be
maintained. During heat dissipation, however, the retia are perfused
unidirectionally in the anterior direction, whereby the temperature
gradient along the nasal mucosa is reduced and heat loss facilitated. In
this situation cooled venous blood, routed by way of the dorsal nasal vein,
may be distributed either to the caval veins directly, for general body
cooling, or, by way of the cavernous sinus that encases the carotid rete,
for selective cooling of the brain.
