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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.
Osteocytes synthesize sclerostin, a secreted protein that inhibits bone formation by binding to LRP5/LRP6 coreceptors and blunting Wnt signaling. [16] [7] Sclerostin, the product of the SOST gene, is the first mediator of communication between osteocytes, bone forming osteoblasts and bone resorbing osteoclasts, critical for bone remodeling. [20]
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).
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 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.
The canal of the nutrient foramen is directed away from more active end of bone when one end grows more than the other. When bone grows at same rate at both ends, the nutrient artery is perpendicular to the bone. Most other bones (e.g. vertebrae) also have primary ossification centers, and bone is laid down in a similar manner. Secondary centers
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.