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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.
The periosteum is a membrane that covers the outer surface of all bones, [1] except at the articular surfaces (i.e. the parts within a joint space) of long bones. (At the joints of long bones the bone's outer surface is lined with "articular cartilage", a type of hyaline cartilage.)
They are part of the outer fibrous layer of periosteum, entering into the outer circumferential and interstitial lamellae of bone tissue. Sharpey's fibres also attach muscle to the periosteum of bone by merging with the fibrous periosteum and underlying bone as well.
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]
The channels are formed by concentric layers called lamellae, which are approximately 50 μm in diameter. The Haversian canals surround blood vessels and nerve cells throughout bones and communicate with osteocytes (contained in spaces within the dense bone matrix called lacunae) through connections called canaliculi.
The lacuna are situated between the lamellae, and consist of a number of oblong spaces. In an ordinary microscopic section, viewed by transmitted light, they appear as fusiform opaque spots. Each lacuna is occupied during life by a branched cell, termed an osteocyte, bone-cell or bone-corpuscle.
Lamella of osteon, the concentric circles around the central Haversian canals; Lamella (cell biology): (i) part of a chloroplast (thin extension of thylakoid joining different grana) (ii) the leading edge of motile cells, containing the lamellipodia; Lamella, a group of land crabs in the family Gecarcinucidae
Bone canaliculi are microscopic canals between the lacunae of ossified bone.The radiating processes of the osteocytes (called filopodia) project into these canals. These cytoplasmic processes are joined together by gap junctions.