Chapter 12 The locomotor system/Fig 12.01.jpg

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Normal bone structure and function. (A) Cortical bone is arranged in concentric cylindrical structures – Haversian systems – here seen in cross-section. (B) Polarization microscopy shows the lamellar structure well. (C) Bone within the medulla forms a meshwork of trabeculae, this is known as cancellous bone; this is also lamellar in type. (D) The cellular composition of bone shown in this photomicrograph is of rapidly formed woven bone with a random arrangement of the collagen fibres. A row (or sheet in three dimensions) of osteoblasts covers the upper surface of the bone: the perinuclear vacuoles are the prominent Golgi apparatus of protein synthesizing and exporting cells. Osteocytes are seen within their lacunae within the bone trabecula. Three active multinucleated osteoclasts lie within resorption cavities on the lower surface.