Osseous tissue, or bone tissue is the major structural and supportive connective tissue of the body. Osseous tissue forms the rigid part of the bone organs that make up the skeletal system.
The bone tissue is a mineralized connective tissue. Bone-forming cells called osteoblasts
deposit a matrix of collagen
, but they also release calcium, magnesium, and phosphate ions, which chemically combine and harden within the matrix into the mineral hydroxyapatite
. The combination of hard mineral and flexible collagen makes bone harder than cartilage
without being brittle. The microscopic structure of mammalian compact bone consists of repeating units called Haversian systems
. Each system has concentric layers of mineralized matrix, called concentric lamellae, which are deposited around a central canal, also known as the Haversian canal, containing blood vessels and nerves that service the bone.
There are two types of osseous tissue and one extra, compact
. Compact bone forms the extremely hard exterior while spongy bone fills the hollow interior. The tissues are biologically identical; the difference is in how the microstructure is arranged.
Osseous tissue performs numerous functions including:
- Support for muscles, organs, and soft tissues.
- Leverage and movement.
- Protection of vital organs. e.g. the heart (Note: some vital organs may not be protected by bones. e.g. the intestines.)
- Calcium phosphate storage.
Osseous tissue versus bones
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 mineral matrix that form the rigid sections of the organ.