Nasal venous drainage in the dog

In the dog, blood from the nasal mucosa may drain via several passageways. Venous outflow measured from the dorsal nasal veins was 30 +/- 1.4 ml/min (of both sides; n = 10) while that from the sphenopalatine veins was 12 +/- 1.0 ml/min (of both sides; n = 10). Nasal venous pressure measured from the dorsal nasal veins was 20 +/- 1.2 mm Hg (n = 10) while that from the sphenopalatine veins was 10 +/- 0.7 mm Hg (n = 10). Occlusion of the dorsal nasal venous outflow increased significantly the sphenopalatine venous outflow whereas occlusion of the sphenopalatine venous outflow had no effect on the dorsal nasal venous outflow. These findings suggest that there are probably two venous systems in the nose; a system of high flow and high pressure draining the anterior nasal cavity and a system of low flow and low pressure draining the posterior nasal cavity.