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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 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 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]
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.
This constitutes the so-called capsule of the space. Each lacuna is generally occupied by a single cell, but during the division of the cells, it may contain two, four, or eight cells. Lacunae are found between narrow sheets of calcified matrix that are known as lamellae (/ l ə ˈ m ɛ l i / lə-MEL-ee).
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.
Lamella, in cell biology, is also used to describe the leading edge of a motile cell, of which the lamellipodia is the most forward portion. [5] The lipid bilayer core of biological membranes is also called lamellar phase. [6] Thus, each bilayer of multilamellar liposomes and wall of a unilamellar liposome is also referred to as a lamella.
The periphery of the ruffled border is surrounded by a ring-like zone of cytoplasm which is devoid of cell organelles but is rich in actin filaments. This zone is called clear zone or sealing zone. The actin filaments enable the cell membrane surrounding the sealing zone to be anchored firmly to the bony wall of Howship's lacunae.