An anatomical investigation of the nasal venous vascular bed in the dog.

Physiological experiments have demonstrated that the canine nasal mucosa has two venous systems that differ in blood pressure and flow. An investigation of the vascular arrangements and histological characteristics of the nasal venous vascular bed was performed to search for anatomical structure(s) responsible for their functional separation. Parietal bicuspid valves were found to be present in both venous systems, being particularly abundant at the two extremities of the nasal cavity and less frequently found over the turbinates. Ostial valves were found to be present guarding the entries of tributaries into the periosteal venous plexus, collecting veins and outflow veins of the nasal mucosa. The collecting veins of the posterior venous system were found to be much larger and to contain a greater amount of muscle than those of the anterior venous system. The parietal valves are suggested to be the anatomical structures responsible for the functional separation of the two venous systems whereas the ostial valves might act as a throttle mechanism, regulating blood flow into the cavernous periosteal venous plexus and the collecting veins of the posterior venous system. The physiological significance of the presence of venous valves and their distribution in the nasal mucosa as well as the probable functions of the collecting veins of the posterior venous system are discussed.