<unk> s (also called Haversian system in honor of Clopton Havers) are predominant structures found in some lamellar or compact bone.<unk> s are  found in many of the bones of many mammals, birds, reptiles, and amphibians running in a meandering way but generally parallel to the long axis of bones. It is this section of compact bone that is called matrix.
In the center of the<unk>  is a central canal, called the Haversian canal.
The central canal is surrounded by concentric layers of matrix called lamellae.  These lamellae are laid down one after the other over time, each successive one inside the preceding one. Collagen fibers in a lamella run parallel to each other but the orientation of collagen fibers across separate lamellae is oblique. The fiber density is also lower at the border between adjacent lamellae, which accounts for the distinctive appearance of an<unk> .<unk> ytes are found between concentric lamellae and connected to each other and the central canal by cytoplasmic processes through the canals called canaliculi. This network permits the exchange of nutrients and metabolic waste.<unk> s are separated from each other by cement lines. Collagen fibers and canaliculi do not cross cement lines.
The space between separate<unk> s is occupied by interstitial lamellae, which were formed by pre-existing<unk> s that have since been reabsorbed.<unk> s are connected to each other and the periosteum by oblique channels called Volkmann's canals.
Osteon
Capitate bone
Hyoid bone
Keloids
Bone
Osteotome
Cartilage
Pisiform bone