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.

Bones are organs that are made up of bone tissue as well as bone marrow, small blood vessels, epithelium and nerves. Bone tissue refers specifically to the bone mineral matrix that forms the rigid sections of the organ, and the bone cells within it. The two types of bone tissue are cortical bone and cancellous bone.

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 blood and nerve supply.

pH balance

Various body systems, including the urinary, respiratory and skeletal systems, interact to maintain the body's proper pH levels. Certain conditions, such as kidney disease, cause an imbalance and lowering of pH levels due to the build-up of H+ ions in the blood. In response to the acidic conditions, bone tissue will dissolve to release calcium carbonate into the bloodstream. The carbonate ions act to neutralize some of the acidity of the blood. However, the loss of calcium carbonate can lead to osteomalacia, the softening of the bones due to the inability to properly construct new bone. With osteomalacia, there is a higher risk for breaks and fractures, similar to osteoporosis.[1][2]

Cortical bone (cross-section). (Osteon 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

References

  1. ↑ "Osteomalacia". Mayo Clinic. Mayo Foundation for Medical Education and Research.
  2. ↑ Saladin, Kenneth (2012). Anatomy and Physiology: The Unity of Form and Function. McGraw Hill. p. 221. ISBN 9780073378251.

Sources

This article is issued from Wikipedia - version of the 11/17/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.