Microscopic Anatomy of Bone

Where are spongy bone and compact bone found?
The outer layer of bone is made of a tough connective tissue called the periosteum.
It is the site of muscle attachment and bone repair.
Beneath the periosteum is a thick layer of compact bone.
At the ends of long bones, the spongy bone layer is found beneath the compact bone.

How do spongy and compact bone differ?

Spongy bone has a lattice-like structure made of tiny beams called trabeculae. These are arranged along lines of stress to resist compression. The spaces between trabeculae contain marrow or blood vessels.
Compact bone is organized into cylinders called osteons, which are made of concentric rings called lamellae.
The lamellae surround a central (Haversian) canal that contains blood vessels and nerves.
These central canals are connected by perforating (Volkmann’s) canals, which run perpendicular to them.

What are the types and functions of specialized bone cells?

Osteocytes – mature bone cells that make up most of the bone tissue.
Osteoclasts – break down old bone tissue.
Osteoblasts – produce new bone tissue.

Canaliculi are tiny channels that connect all bone cells, allowing them to receive nutrients and remove waste.

Summary:
Spongy bone has many open spaces, while compact bone is made of tightly packed osteons. Specialized bone cells build, break down, and maintain bone tissue, while canaliculi keep all the bone cells connected and nourished.