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A bone is a rigid organ [1] that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility.
The axial skeleton (80 bones) is formed by the vertebral column (32–34 bones; the number of the vertebrae differs from human to human as the lower 2 parts, sacral and coccygeal bone may vary in length), a part of the rib cage (12 pairs of ribs and the sternum), and the skull (22 bones and 7 associated bones).
Bone mineral is formed predominantly from carbonated hydroxyapatite [1] [2] with lower crystallinity. [1] [3] Bone mineral is formed from globular and plate structures [3] [4] distributed among the collagen fibrils of bone and forming yet a larger structure. The bone salt and collagen fibers together constitute the extracellular matrix of bone
This can be done in terms of the chemical elements present, or by molecular structure e.g., water, protein, fats (or lipids), hydroxyapatite (in bones), carbohydrates (such as glycogen and glucose) and DNA. In terms of tissue type, the body may be analyzed into water, fat, connective tissue, muscle, bone, etc.
Including the bones of the middle ear and the hyoid bone, the head contains 29 bones. Cranial bones (8) Occipital bone; Parietal bones (2) Frontal bone; Temporal bones (2) Sphenoid bone (sometimes counted as facial) Ethmoid bone (sometimes counted as facial) Facial bones (15) Nasal bones (2) Maxilla (upper jaw) (2) Lacrimal bone (2) Zygomatic ...
Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. [2] In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). [3] It is composed of hematopoietic cells, marrow adipose tissue, and supportive stromal cells.
The body is composed of cancellous bone, which is the spongy type of osseous tissue, whose microanatomy has been specifically studied within the pedicle bones. [4] This cancellous bone is in turn, covered by a thin coating of cortical bone (or compact bone), the hard and dense type of osseous tissue. The vertebral arch and processes have ...
One hypothesis is that bone developed from tissues that evolved to store minerals. Specifically, calcium-based minerals were stored in cartilage and bone was an exaptation development from this calcified cartilage. [5] However, other possibilities include bony tissue evolving as an osmotic barrier, or as a protective structure.