Examine the two samples of compact, lamellar bone on slide 32.

• This unstained tissue was not decalcified and was prepared as thin wafers using a grinding stone rather than a microtome.
• Cells are not preserved by this method, but the lamellae, lacunae, and canaliculi of osteons (Haversian systems) are shown very well (Figs. 8-9 and 8-10).
• Study both specimens on slide 32 for longitudinal and transverse orientations of osteons. Identify Haversian canals and if possible Volkmann’s canals, connecting channels between neighboring osteons.

Draw a group of 3 osteons cut transversely, showing all the structures listed above.

What structures occupied the various cavities of osteons in the living tissue?

What is the significance of the irregular "interstitial systems" seen in transverse specimen?

Clinical note: The normal balance between bone deposition and absorption is influenced by steroid hormones and in older individuals this balance is disturbed and there is slow, progressive reduction in bone mass per unit volume. This occurs in both sexes but is accelerated in women after menopause and often leads to osteoporosis (image at right), in which the reduction in mass of cortical bone and the number of trabeculae makes the bones fragile.

Now let's consider bone and joint formation.