Final answer:
Compact bone's basic unit is the osteon, composed of lamellae surrounding a Haversian canal. Articular cartilage covers the bone's epiphysis, while spongy bone provides strength. The medullary cavity contains yellow marrow and is lined by the endosteum.
Step-by-step explanation:
The basic microscopic unit of compact bone is called an osteon (or Haversian system). Osteons are structural units that can measure several millimeters long and about 0.2 mm in diameter. Each osteon is composed of concentric rings of calcified matrix known as lamellae, surrounding a central canal called the Haversian canal, which contains blood vessels, nerves, and lymphatic vessels. The osteocytes, which are mature bone cells, reside in small spaces called lacunae and receive nutrition through tiny channels called canaliculi that connect to the central canal.
Articular cartilage is a thin layer covering the epiphysis of a long bone, providing reduced friction and acting as a shock absorber during movement. Spongy bone is found within the epiphysis and is composed of a network known as trabeculae which provides the bone with strength and resilience. The medullary cavity within the diaphysis of long bones is lined with a delicate membrane called the endosteum and is filled with yellow marrow.