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Haversian canals [i] (sometimes canals of Havers, osteonic canals or central canals) are a series of microscopic tubes in the outermost region of bone called cortical bone. They allow blood vessels and nerves to travel through them to supply the osteocytes .
Each osteon consists of concentric layers, or lamellae, of compact bone tissue that surround a central canal, the Haversian canal. The Haversian canal contains the bone's blood supplies. The boundary of an osteon is the cement line. Each Haversian canal is surrounded by varying number (5-20) of concentrically arranged lamellae of bone matrix.
It facilitates bone's main functions—to support the whole body, to protect organs, to provide levers for movement, and to store and release chemical elements, mainly calcium. It consists of multiple microscopic columns, each called an osteon or Haversian system.
X 100. a, Haversian canals; b, lacunae seen from the side; ... In histology, a lacuna is a small space, containing an osteocyte in bone, [1] or chondrocyte in cartilage.
In cartilage, the lacunae and hence, the chondrocytes, are isolated from each other. Materials picked up by osteocytes adjacent to blood vessels are distributed throughout the bone matrix via the canaliculi. Diameter of canaliculi in human bone is approximately 200 to 900 nm. [1]
Hyaline cartilage is the most common kind of cartilage in the human body. [2] It is primarily composed of type II collagen and proteoglycans. [2] Hyaline cartilage is located in the trachea, nose, epiphyseal plate, sternum, and ribs. [2] Hyaline cartilage is covered externally by a fibrous membrane known as the perichondrium. [2]
The cell also exhibits a reduced size endoplasmic reticulum, Golgi apparatus and mitochondria, and cell processes that radiate largely towards the bone surfaces in circumferential lamellae, or towards a haversian canal and outer cement line typical of osteons in concentric lamellar bone. [5]
Volkmann's canals, also known as perforating holes or channels, are anatomic arrangements in cortical bones that allow blood vessels to enter the bones from periosteum.They interconnect the Haversian canals (running inside osteons) with each other and the periosteum.