Scanning electron microscopy of human ossicles.

Human middle ear ossicles removed from cadavers and during surgical procedures have been examined with scanning electron microscope (SEM). Two kinds of bone tissue compose ossicles: periosteal and endochrondral bone. Periosteal bone occurs in the form of external covering on the ossicles. In the middle of the ossicles there is endochrondral bone which shows various spatial arrangement of collagen bundles. Lamellar bone occurs also in this bone around vascular channels but rarely in the form of typical osteons. Surface appearance of periosteal, coarse-fibred bone and lamellar, fine-fibred bone is almost the same. Lamellar bone is composed of coarse collagen bundles arranged tightly in the rows. The space between the rows is filled by fine fibres which link the coarse bundles.