Biology

BONE, LOWER MAGNIFICATION:

Mature bone is composed of hard ground substance, most of which is layered in a circular fashion.  There are living cells that are embedded within the ground substance or line the larger spaces, called Haversian canals (H), where blood vessels traverse.  The small dark streaks visible in this image are where individual cells are located; these cells are called osteocytes (OS).

BONE, HIGHER MAGNIFICATION:

The Haversian canals (H), where the blood vessels pass through the dense bone, are surrounded by lamellar bone arranged in concentric circles.  The dark streaks within the lamellar bone are where the osteocytes (OS) reside.  They are connected to one another and the Haversian canal by very thin channels called canaliculi (arrowheads).  These are those spider web-like extensions you see between adjacent osteocytes.