骨(bone)
脊椎动物体内坚硬的结缔组织，主要由坚硬的骨基质和嵌在其中的骨细胞构成。骨骼是身体的支撑框架，提供肌肉运动的附着点，保护内部组织，包裹造血系统（红骨髓），也是对许多身体过程有非常重要意义的钙的贮库，全身99%的钙存於此。骨由镶嵌在胶原纤维中的钙、磷和碳晶体的基质和骨细胞（少於骨体积的5%）组成，胶原纤维提供强度和弹性。骨的外层为质密的骨皮质，包围着海绵状骨松质中心区（不算骨髓腔）。骨不是透过细胞分裂来生长的，而是由不同种类的骨细胞产生骨基质，使其分裂并维持它。透过这一过程反覆模制出骨头来，在最大压力的地方加强，让断口处癒合，并调节体液里钙的水平（参阅calcium deficiency）。这一过程也会造成不常用到的骨头（如不能运动的肢体）发生萎缩。骨骼方面的疾病包括类风湿性关节炎、骨关节炎、佝偻病、骨质疏松和肿瘤等。骨头在重压下会突然或逐渐断裂。
English version：
bone
Rigid connective tissue of vertebrates consisting of cells embedded in a hard matrix. Bones serve as the body's supporting framework; provide muscle attachment points for movement; protect the internal organs; house the blood-cell formation system (red bone marrow); and hold about 99% of the calcium vital to many body processes. Bone consists of a matrix of calcium, phosphate, and carbonate crystals embedded among collagen fibers, providing strength and elasticity, and bone cells (less than 5% of its volume). An external layer of compact bone surrounds a central area of spongy bone, except at the marrow cavity. Bone does not grow by cell division; instead, different types of bone cells generate bone matrix, break it down, and maintain it. Bone is remodeled by this process, which strengthens it in areas under greatest stress, permits healing of fractures, and helps regulate calcium levels in body fluid (see calcium deficiency). The process also causes underutilized bone, as in an immobilized limb, to atrophy. Bone disorders include rheumatoid arthritis, osteoarthritis, rickets, osteoporosis, and tumors. Bone can fracture suddenly or over time, as in stress fractures.