The main difference between cortical and cancellous bone is that cortical bone is the external layer of all bones of the appendicular skeleton, whereas cancellous bone is the bone that occurs between the cortices of the flat and short bones of the axial skeleton.
Cortical and cancellous bones are two types of bone that occur in the human skeleton. The main function of these bones is to provide structural support while aiding in movement.
Key Areas Covered
1. What is Cortical Bone
– Definition, Structure, Function
2. What is Cancellous Bone
– Definition, Structure, Function
3. Similarities Between Cortical and Cancellous Bone
– Outline of Common Features
4. Difference Between Cortical and Cancellous Bone
– Comparison of Key Differences
Key Terms
Cortical Bone, Cancellous Bone
What is Cortical Bone
Cortical bone is the hard outer shell of the long bones, also known as compact bone. Generally, the strongest and densest bones of the skeleton are compact bones. Compact bones consist of tiny passages for both blood vessels and nerves to maintain and repair the bone. A compact bone is covered by a periosteum from the outside. The inner surface of the bone is covered by the endosteum, a thin, vascular connective tissue that lines the long bones’ marrow cavity. The marrow cavity occurs at the shaft of the long bones called diaphyses. It consists of yellow bone marrow, which stores fat.
Figure 1: Compact and Spongy Bone
Furthermore, cortical bone consists of osteocytes, surrounded by a solid extracellular matrix. Hydroxyapatite is a mineral that is found in the extracellular matrix of bones. Generally, it is rich in calcium and phosphorous. Collagen fibers intersperse in the hydroxyapatite, giving some sort of flexibility to the bone. Osteons make up the structure of the compact bone that surrounds tiny central canals.
What is Cancellous Bone
Cancellous bone is the osseous tissue found in the middle of the bones. Generally, it is known as spongy bone. Cancellous bones are less dense and lighter than compact bones. They also occur in the interior portion of the long bones. The matrix of the bone is composed of mineral bars called trabeculae, which form a three-dimensional latticework. Red bone marrow and blood vessels fill the space of the latticework. Canaliculi connect the spaces to each other by canaliculi. Red bone marrow produces blood cells in a process called hematopoiesis.
Figure 2: Long Bone
Moreover, spongy bone forms the enlarged ends of the long bones called epiphyses. They are the major components of the ribs, shoulder blades, and flat bones of the skull. Most of the short flat bones of the skeleton are spongy bones. Spongy bones show relatively high metabolic activity as well. The spongy bones transform into compact bones by the action of osteoblasts. Osteoblasts deposit new bone matrix around the trabeculae. Therefore, the space between trabeculae becomes limited eventually.
Similarities Between Cortical and Cancellous Bone
- Cortical and cancellous bones are two types of bones that occur in the skeleton.
- They provide structural support to the body while aiding in movement.
Difference Between Cortical and Cancellous Bone
Definition
Cortical bone refers to the strong and compact type of bone found on the outer layer of the long bones, while cancellous bone refers to the spongy, porous, honeycomb-like structure and is typically found at the ends of long bones.
Also Known As
Cortical bone is also known as a compact bone, while cancellous bone is also known as spongy bone or trabecular bone.
Structure
Moreover, cortical bone is the non-cancellous part of the bone, consisting of closely-packed osteons, forming a hard exterior, while cancellous bone fills the interior cavity of the bone, consisting of mineralized bars known as trabeculae.
Marrow Cavity
Cortical bone has a marrow cavity, while cancellous bone does not have a marrow cavity.
Bone Marrow
Cortical bone contains yellow bone marrow, while cancellous bone contains red bone marrow.
Occurrence
Furthermore, cortical bone occurs in long bones such as arms and legs, while cancellous bone occurs in wrists and ankles.
Conclusion
In brief, cortical and cancellous bone are two types of bone that occur in the human skeleton. The main function of bones is to provide structural support to the body while aiding movement. Generally, compact bone is another name for the cortical bone that contains a marrow cavity filled with yellow bone marrow. In addition, it occurs in long bones and consists of osteons. Cancellous bone, on the other hand, does not contain a marrow cavity but contains red bone marrow. Normally, it occurs in the wrists and ankles. Overall, the main difference between cortical and cancellous bone is the structure of bone.
References:
- Types of bone. Orthobullets. (n.d.). Retrieved January 27, 2023
Image Courtesy:
- “Illu compact spongy bone” By SEER – Own work (Public Domain) via Commons Wikimedia
- “Left femur of extinct elephant, Alaska, Ice Age Wellcome L0057714” By Fae – Own Work (CC BY 4.0) via Commons Wikimedia
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