Bone tissue

Bone tissue

Cross-section of a long bone showing both spongy and compact osseous tissue

Anatomical terminology

Bone tissue, or osseous tissue, is the major structural and supportive connective tissue of the body. Bone tissue forms the rigid part of the bones that make up the skeleton.

Bone tissue is different from bones themselves — bones are organs made up of bone tissue as well as marrow, blood vessels, epithelium and nerves, while bone tissue refers specifically to the bone mineral matrix that forms the rigid sections of the organ, and the bone cells within it.

Structure

There are two types of bone tissue: cortical bone and cancellous bone. Cortical bone is synonymous with compact bone, and cancellous bone is synonymous with trabecular and spongy bone. Cortical bone forms the extremely hard exterior while cancellous bone fills the hollow interior. The tissues are biologically identical; the difference is in how the microstructure is arranged.

Formation

Bone tissue is a mineralized connective tissue. It is formed by cells, called osteoblasts, that deposit a matrix of Type-I collagen and also release calcium, magnesium, and phosphate ions that ultimately combine chemically within the collagenous matrix into a crystalline mineral, known as bone mineral, in the form of carbonated hydroxyapatite. The combination of hard mineral and flexible collagen makes bone harder and stronger than cartilage without being brittle. Cortical bone consists of a repeating structure called an osteon or Haversian system, which is the primary anatomical and functional unit. Each osteon has concentric lamellae (layers) of mineralized matrix, which are deposited around a central canal, known as the Haversian canal, each containing a blood and nerve supply.

Compact bone (cross-section). (Haversian system and osteocytes).
Osteoblasts. actively synthesizing osteoid with two osteocytes.
Osteoclast with multiple nuclei and a "foamy" cytosol.

Function

Bone tissue performs numerous functions including:

Directly:

Indirectly:

See also

Sources

This article is issued from Wikipedia - version of the Wednesday, February 03, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.