Figure 3.

Diagram showing the anatomical arrangement for evaporative respiratory heat loss. The complex system of turbinate bones in the upper respiratory tract is covered by a mucous membrane with a rich blood supply and numerous AVAs, so that when blood enters the nose on inhalation it is cooled and, when necessary, gains direct access to the venous side of the circulation via the AVAs. Venous transporters such as the angularis occuli referred to as orbital vein in this diagram, drain the face and scalp and flow into the cavernous sinus at the base of the brain. The facial vein transports cooled blood from the upper respiratory tract directly into the jugular vein, thence to the right heart and central circulation, effectively contributing to whole body cooling. Diagram with permission from Dr. Finola McConaghy, PHD thesis 1995. (Blue represents venous blood; red represents arterial blood).