What is the Difference Between Cancellous and Cortical Bone?

Cancellous and cortical bones are two types of osseous tissues that make up the human skeleton, and they have distinct structures and functions. Here are the main differences between them:

• Density and Structure: Cortical bone is dense and contains less than 10% soft tissue, while cancellous bone is made up of trabecules shaped as plates or rods interspersed between bone marrow, representing more than 75% of the cancellous bone volume. Cancellous bone is less dense, softer, weaker, and less stiff than cortical bone.
• Function: Cortical bones provide strength and protection to bones, supporting the whole body weight, protecting organs, providing levers for movement, and storing and releasing calcium. Cancellous bones, on the other hand, have a higher surface area and are ideal for metabolic activity, such as the exchange of calcium ions. They also produce red blood cells and white granular corpuscles in their bone marrow.
• Distribution: Cortical bones make up most of the skeletal system (up to 80%), while the rest is cancellous bones (roughly 20%). Cortical bone forms a protective layer around the internal cavity of bones, while cancellous bone typically occurs at the ends of long bones.
• Microscopic Appearance: Microscopically, both cortical and cancellous bones are identical, consisting of an extracellular matrix composed mainly of type 1 collagen.
• Vascularity: Cancellous bone is highly vascular, frequently containing red bone marrow where hematopoiesis, the production of blood cells, occurs. In osteoporosis, cancellous bone is more severely affected than cortical bone.

Comparative Table: Cancellous vs Cortical Bone

Here is a table comparing the differences between cancellous and cortical bone:

In summary, cancellous bone is a light, porous bone found mainly in the axial skeleton, while cortical bone is dense and found on the outer surface of bones. Cancellous bone has parallel lamellae and produces red blood cells and white granular cells, while cortical bone has concentric lamellae and stores fat.