Haversian Systems are cylindrical structures of compact bone, which in transverse section are seen to be formed of 4-20 regular concentric lamella surrounding a central vascular channel (Haversian canal). 
Each Haversian canal contains a blood vessel involved in the common nutrition of the compact bone. The blood vessels of the Haversian canals are supplied with blood from vessels from the periosteum. These blood vessels penetrate the Haversian system in a transverse direction and are known as Volkmanns canals. Volkmann's canals can be identified as they do not have concentric lamella surrounding them.