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The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
Bone canaliculi are microscopic canals between the lacunae of ossified bone.The radiating processes of the osteocytes (called filopodia) project into these canals. These cytoplasmic processes are joined together by gap junctions.
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.
In embryogenesis, the skeletal system is derived from the mesoderm germ layer. Chondrification (also known as chondrogenesis) is the process by which cartilage is formed from condensed mesenchyme tissue, which differentiates into chondroblasts and begins secreting the molecules (aggrecan and collagen type II) that form the extracellular matrix.
Enamel is the hardest substance in the human body and contains the highest percentage of minerals, [3] 96%, with water and organic material composing the rest. [4] The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate. [5]
Primary bone cancer is a type of sarcoma, a cancer that originates in bone, muscle, fibrous tissue, blood vessels, fat tissue, as well as some other tissues. [2] Primary bone cancer can arise in any of the 206 bones in the body but is mostly seen to originate the arms and the legs. [3]
Spinalis dorsi, the medial continuation of the sacrospinalis, is scarcely separable as a distinct muscle.It is situated at the medial side of the longissimus dorsi, and is intimately blended with it; it arises by three or four tendons from the spinous processes of the first two lumbar and the last two thoracic vertebrae: these, uniting, form a small muscle which is inserted by separate tendons ...
A coccyx with four vertebrae below the sacrum. The coccyx is formed of three, four or five rudimentary vertebrae.It articulates superiorly with the sacrum.In each of the first three segments may be traced a rudimentary body and articular and transverse processes; the last piece (sometimes the third) is a mere nodule of bone.