The sodium pump and the bicarbonate-chloride exchanger at the opposite basolateral surface maintain the intracellular pH of the osteoclast as it performs its activities. In the acidic extracellular space, mineral is leached from the adjacent bone, and acid proteinases degrade the organic matrix components. The protein encoded by the c- src oncogene, also important in osteoclast differentiation and function, has been found at the ruffled border. Knockout of the c- src gene in transgenic mice produces defective osteoclasts and inhibits bone resorption in these animals, which may manifest as osteopetrosis or marble bone disease. Woven bone is the characteristic tissue in the developing embryo.
Lamellar bone is the characteristic component of the normal adult skeleton.
Woven bone and lamellar bone are easily identified under a polarizing microscope. The arrangement of collagen fibers in each produces a unique pattern of birefringence and probably determines the specific structural effects of the two tissue types. Woven bone contains nonparallel arrays of collagen fibers arranged in an irregular, haphazard pattern. There is a high concentration of cells per unit of matrix, and the cells present a variety of shapes and sizes. Lamellar bone is characterized by an orderly array of collagen fibers aligned in parallel.