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Histology of compact bone showing osteon. 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.
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. Lacunae are connected to one another by small canals called canaliculi. A lacuna never contains more than one osteocyte.
Cancellous bone or spongy bone, [12] [11] also known as trabecular bone, is the internal tissue of the skeletal bone and is an open cell porous network that follows the material properties of biofoams. [13] [14] Cancellous bone has a higher surface-area-to-volume ratio than cortical bone and it is less dense. This makes it weaker and more flexible.
Diameter of canaliculi in human bone is approximately 200 to 900 nm. [1] In bovine tibia diameter of canaliculi was found to vary from 155 to 844 nm (average 426 nm). [ 2 ] In mice humeri it varies from 80 to 710 nm (average 259 nm), while diameter of osteocytic processes varies from 50 to 410 nm (average 104 nm).
It is composed of 270 bones at the time of birth, [2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired. [3] Many small accessory bones, such as sesamoid bones, are not included in this.
Endochondral ossification is the process by which most vertebrate axial skeletons form into hardened bones from cartilage. This process begins with a cartilage anlage where chondrocyte cells will congregate and start their maturation process. Once the chondrocytes have fully matured at the desired rate, the cartilage tissue will harden into ...
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.)
In histology, osteoid is the unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue. [1] Osteoblasts begin the process of forming bone tissue by secreting the osteoid as several specific proteins. The osteoid and its adjacent bone cells have developed into new bone tissue when it becomes mineralized.