Fibrillar bone can be distinguished from Lamellar bone because of the spatial organisation of the extracellular matrix of bone (EMB). Whereas the collagen bundles in fibrillar bone are all arranged in all directions, the structure of the lamellar bone is regular.
Fibrillar bone (or primary or immature, during development or recovery from fracture is therefore formed wherever bone tissue has to be produced very quickly whereas lamellar (or mature) bone is secondary and requires more time to form. Lamellar bone is formed from spongiform or canalicular bone (Spongiosa) and compact bone (Kompakta), which are both lamellar structures. They differ only in how their fibres are arranged. Spongiform bone is formed from flat fibres parallel to the surface whereas compact bone is formed from concentric fibres arranged around a blood vessel. The lamellar structure can be seen under a polarising microscope.