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What are compact bone and cancellous bone?

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Front and back views of the human skeleton are shown side by side, with labeled bones including the skull, spine, ribs, pelvis, arms, legs, hands, and feet. Insets detail the bones of the foot and hand, highlighting major bone groups and anatomical terms. — human skeleton Front and back views of the human skeleton.

The human skeleton is composed of two primary types of bone tissue that work together to provide structural support, protection, and flexibility.

Compact Bone

Compact bone is a dense, hard tissue that makes up approximately 80 percent of the human skeleton. It forms a protective shell around the interior of bones and is the primary component of long bones in the arms and legs, where high strength and rigidity are required. Structurally, it consists of concentric layers organized into units called osteons, which contain vascular canals to supply bone cells with nutrients.1

Cancellous Bone

Cancellous bone, also known as spongy or trabecular bone, accounts for about 20 percent of the skeleton. It has a porous, honeycombed appearance created by a three-dimensional lattice of bony processes called trabeculae. This structure is lightweight and flexible, making it ideal for dampening sudden stresses in joints and supporting areas with less mechanical load, such as the ends of long bones, the ribs, and the skull. The spaces within this lattice are often filled with bone marrow, which is essential for blood cell production.23