What is the Difference Between Cancellous and Cortical Bone

The key difference between cancellous and cortical bone is that cancellous bones form the ends or epiphyses of long bones while cortical bones form the shaft or diaphysis of long bones.

The human skeletal system is made up of 206 bones. All bones are mainly divided into two categories: cancellous bones and cortical bones. Out of these two types of bones, cortical bones make up most of the skeletal system (up to 80%), while the rest is cancellous bones.

1. Overview and Key Difference
2. What is a Cancellous Bone
3. What is a Cortical Bone
4. Similarities – Cancellous and Cortical Bone
5. Cancellous vs Cortical Bone in Tabular Form
6. Summary – Cancellous vs Cortical Bone

What is a Cancellous Bone?

Cancellous bone is a light, porous bone that encloses large spaces, giving them a spongy nature or appearance. It is also known as trabecular or spongy bone. The matrix of the bone is structured in a three-dimensional lattice of bony processes called trabeculae. They arrange along the stress lines and help to withstand stress. The spaces in between are filled with blood vessels and marrow. About 20 percent of the human skeleton is made of cancellous bone.

Cancellous bones provide structural support and flexibility. They are present in the enlarged ends of the long bones and are a major component of ribs, flat bones of the skull, shoulder blades, and short, flat bones in the other parts of the skeleton. A shell of compact bone surrounds the cancellous bone. This provides strength and rigidity. Cancellous bones develop into compact bones through bone-forming cells known as osteoblasts. All long bones develop in this manner in the embryo. Osteoblasts deposit bone matrix around the trabeculae in layers. This enlarges the space between them. Spaces then disappear, and immature compact bones are produced. Different proportions of space to bone are found in various bones, depending on the strength and flexibility the bones require. Cancellous bones have relatively high metabolic activity. The bone marrow of cancellous bones produces red blood corpuscles and white granular corpuscles. But cortical bones lack a bone marrow cavity.

What is a Cortical Bone?

Cortical bone is the bone that forms a protective layer around the internal cavity. The cortical bone makes up almost 80 % of the skeletal muscle mass. Cortical bones possess high resistance to bending and torsion; hence they are able to bear the weight of the body. Cortical bones often lead to diseases such as osteoporosis. In addition, trauma to cortical bones in the spine, arm, and legs can cause severe effects.

The primary function of a cortical bone is to provide strength and protection to other bones. A cortical bone is relatively smooth in comparison to a cancellous bone, and it is white in color. The structure of the cortical bone consists of many layers. The most outside layer of the cortical bone is the periosteum, which is a two-layered structure. This layer protects the nerves and blood vessels that run through the cortical bone. The interior layer of the periosteum consists of osteoblasts, which synthesize bone matrix. Cortical bones consist of a bone marrow cavity in the center, which stores fat.

What are the Similarities Between Cancellous and Cortical Bone?

Cancellous and cortical bones are two types of bones present in the human body.
They consist of bone cells.
Moreover, they provide a rigid structure to the body.
Both bones consist of bone marrow.
Both cancellous and cortical bones help in mobility and flexibility of the body.

What is the Difference Between Cancellous and Cortical Bone?

Cancellous bones form the ends or epiphyses of long bones, while cortical bones form the shaft or diaphysis of long bones. This is the key difference between cancellous and cortical bone. Cancellous bones are made up of trabeculae, whereas cortical bones are made up of osteons. Moreover, the bone marrow of cancellous bones produces red blood corpuscles and white granular corpuscles, while the bone marrow of cortical bones stores fat.

The following table summarizes the difference between cancellous and cortical bones.

Summary – Cancellous vs Cortical Bone

The human skeletal system comprises 206 bones categorized into two categories: cancellous bones and cortical bones. Cancellous bones form the ends or epiphyses of long bones, while cortical bones form the shaft or diaphysis of long bones. Cancellous bone is a light, porous bone that encloses large spaces and has a spongy nature or appearance. They provide structural support and flexibility. Cortical bone is the bone that forms a protective layer around the internal cavity. Cortical bones make up almost 80 % of the skeletal muscle mass. Cortical bones possess high resistance to bending and torsion, hence aiding in bearing the weight of the body. This summarizes the difference between cancellous and cortical bone.

Reference:

1. “Cancellous Bone.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.
2. “Cortical Bone.” Spine Health.

Image Courtesy:

1. “606 Spongy Bone” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “Bone cross-section” By Pbroks13 – Own work (CC BY 3.0) via Commons Wikimedia