Fig. 1.

Novel concepts related to the bone vasculature. Transcortical vessels (TCVs) are important vascular structures that originate in the bone marrow and traverse cortical bone canals perpendicularly along the bone shaft, eventually joining the direct periosteal circulation. Over 80% of the arterial blood stream and 59% of the venous blood flow passes through TCVs. TCVs located across the narrow canals of cortical bone provide an orientation for immune cells and hematopoietic stem cells (HSCs) to migrate from the bone marrow to the general outer peripheral circulation and help mediate highly effective blood exchange between the microvasculature in the internal and external circulation