Explain Haversian system.

Explanation

The compact bone consists of several structural units called Osteons or Haversian systems arranged around and parallel to the bone marrow cavities:
Haversian system consists of a Haversian canal that runs parallel to the marrow cavity. It contains an artery, a vein and a lymphatic vessel. Haversiari canal is surrounded by concentric lamellae. Small fluid filled spaces called .lacunae provided with minute canaliculi lie in between the lamellae. Canaliculi connect the lacunae with one another and with Haversian canal. Each lacuna encloses one osteocyte (inactive form of osteoblast). The cytoplasmic processes of osteocytes extend through canaliculi. A Haversian canal and the surrounding lamellae and lacunae are collectively called a Haversian system or osteon. The Haversian canals communicate with the marrow cavity by transverse or oblique canals called Volkmann.s canals. Nutrients and gases diffuse from the vascular supply of Haversian canals.