Osteocytes, light micrograph. Osteocytes embedded in bone matrix. Osteocyte nuclei are surrounded by lacunae seen as empty haloes. Cytoplasmic processes numbering from 50-80 per cell extend into the bone matrix and their total surface area in the human skeleton is estimated to be 200 square metres. Osteocytes regulate the exchange of calcium and phosphate ions between bone and the vascular system. Paraffin section. Massons trichrome stain. Magnification: x600 when printed at 10cm.