This is composed of numerous systems of concentrically arranged bony lamellae, around a central canal, the Haversian canal, which run longitudinally and encloses blood vessels. Each concentric system is known as a Haversian system or Osteon.
Haversian canals of adjacent systems are inter connected by transverse channels and volkmann’s canals connect haversian canals with periosteal and endosteal surfaces.
In a cross section of the bone, the Haversian canals are seen to be surrounded by a varying number (8 to 15) of concentric lamellae. These concentric lamellae and the central canal constitute a Haversian system or Osteone. In the periphery, the lamellae are not concentric but run parallel with the surface and form a relatively thin outer layer of the bone, the outer circumferential or general lamellae. Similarly arranged inner circumferential lamellae separate the Haversian systems from the marrow cavity.
Finally, the intervals between the Haversian lamellae are occupied by more irregular layers of bone which constitute the intertitial lamellae. Adjacent lamellar systems are as a rule sharply delimited from each other by a dark staining thin layer of modified matrix (cement membrane, cement line).
