Batson's plexus, also known as the vertebral venous plexus, is a network of valveless veins in the human body that connects the deep pelvic veins and thoracic veins to the internal vertebral venous system. This plexus is clinically significant because it provides a pathway for the spread of infections and metastases, particularly to the spine, due to its valveless nature and bidirectional blood flow.