The internal vertebral venous system is a network of valveless veins located within the vertebral column, providing a pathway for venous blood to flow between the brain and the body, particularly significant in the context of increased intra-abdominal pressure. This system is clinically important as it can serve as a route for the spread of infections or metastases due to its connections with the cranial venous sinuses and the venous plexuses of the body.