Osseous tissue, or bone, is a living tissue, composed of a mixture of organic and non-organic substances. Bone tissue can be described according to its level of structure: macro-, micro-, sub-micro-, nano-, and sub-nano-. At the macroscopic level, bone can be classified as cortical or cancellous, organised microscopically as osteons and trabeculae respectively. At the sub-microstructure level bone can be lamellar or non-lamellar, while at the cellular level, bone consists principally of three main cell types: osteoclasts, osteoblasts, and osteocytes, which interact to continuously regenerate the bone matrix. Bone is continuously modelling/remodelling itself throughout an individual’s life, allowing the skeleton to increase in size during growth, respond to physical stresses, and repair structural damage due to fatigue, failure or trauma. Bone homeostasis is only maintained if the processes of resorption and formation are closely coupled. Understanding the micro- and macro-architecture of bone and the processes involved in bone remodelling are crucial in the diagnosis of osteoporosis and the evaluation of the effectiveness of treatments and interventions. The purpose of this article (the first of a three-part feature) is, therefore, to describe the structure and function of bone, the cells involved in bone remodelling, and the process of remodelling itself.

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