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Compact vs Spongy Bone: A Detailed Evaluation

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Last updated date: 28th Feb 2024
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Difference Between Compact and Spongy Bone: All You Need to Know!

The human body has 206 bones. Out of them, two important structural bones are- compact and spongy bones. But, do they have similar features? They do not. It's why there are a lot of points to describe compact vs spongy bone. These are mostly based on common categories like structure, composition, surface area, blood supply, elasticity, calcium storage, etc. Are these all? You'll have to go through the below article to find out! Not only that but the article also explains their similarities. So, go ahead and help yourself!

What is Compact and Spongy Bone?

Before learning compact vs spongy bone, it's important to explain compact and spongy bone. Why? Because once you have a proper understanding of both bones, individually, you can easily understand the compact and spongy bone difference. So, keep reading the below sections to learn about both- spongy and compact bones. 

Compact Bone

Compact bone, is otherwise also called cortical bone, forms the outer layer of bones. It is dense and strong, providing protection and support. It contains tightly packed osteons or Haversian systems, which consist of concentric rings of the mineralized matrix surrounding a central canal that houses blood vessels and nerves.


Spongy Bone

Spongy bone, also called cancellous or trabecular bone, is found inside the bone, beneath the compact bone layer. It consists of a lattice-like network of trabeculae, which are thin columns or plates of bone tissue. Spongy bone provides structural support while reducing the weight of the bone and housing red bone marrow.


Compact vs Spongy Bone

Compact vs spongy bone is a very important topic that needs to be covered during NEET preparation. Are you wondering the difference between compact and spongy bone? Find in the table below:


S.No.

Category

Compact Bone

Spongy Bone


Structure

Consists of trabeculae (small, interconnected beams) with open spaces in between.

Consists of densely packed osteons (Haversian systems).



Location

Found at the ends of long bones, in the interior of flat bones, and the epiphyses of irregular bones.

Forms the outer layer of all bones and the diaphyses of long bones.


Strength

Less dense and lighter, making it more flexible.

Highly dense and rigid, providing strength and support.


Composition

Composed of a lattice-like network of trabeculae, with spaces filled with red bone marrow.

Composed of concentric lamellae surrounding Haversian canals, which contain blood vessels and nerves.


Blood Supply

Blood vessels are present within the trabeculae, supplying nutrients and removing waste products.

Blood vessels are primarily present within the Haversian canals, which penetrate through the concentric lamellae.


Fracture Healing

Heals faster due to the presence of red bone marrow, which aids in the production of new blood cells and tissue regeneration.

Healing may take longer due to a slower blood supply and limited regenerative capabilities.


Surface Area

The large surface area due to the complex network of trabeculae, facilitating metabolic exchange and nutrient diffusion.

The smaller surface area due to dense packing, limiting metabolic exchange.


Strength-to-Weight Ratio

Lower strength-to-weight ratio.

Higher strength-to-weight ratio.


Resorption

More prone to resorption and remodeling.

Less prone to resorption and remodeling.


Elasticity

More elastic and capable of absorbing shocks and impacts.

Less elastic and more brittle.



Red Bone Marrow

Contains a higher concentration of red bone marrow, responsible for hematopoiesis (blood cell production).

Contains a lower concentration of red bone marrow, which decreases with age.


Yellow Bone Marrow

Contains less yellow bone marrow (adipose tissue).

Contains more yellow bone marrow, which serves as a fat storage site.


Calcium Storage

Lower capacity for calcium storage.

Higher capacity for calcium storage.


Bone Formation

Participates in bone formation during growth and remodeling.

Less involved in bone formation, primarily maintaining bone integrity.


Metabolic Activity

Higher metabolic activity due to increased surface area and blood supply.

Lower metabolic activity compared to spongy bone.


Trabecular Orientation

Trabeculae are arranged in a network pattern, providing strength in multiple directions.

Lamellae are arranged parallel to each other, providing strength in one direction.


Mechanical Properties

More flexible and capable of absorbing stresses from various directions.

More rigid and capable of withstanding higher mechanical loads.


X-Ray Appearance

Appears less dense on X-ray images due to the open spaces between trabeculae.

Appears denser on X-ray images due to the tightly packed lamellae.


Similarities: Characteristics of Compact and Spongy Bone 

While there are many points explaining compact vs spongy bone, there are also similarities between them. Some important ones are discussed in the below-mentioned points:


  • Bone tissue is used to compose both compact and spongy bones.

  • Calcium is stored in both of these bones.

  • They provide strength and protection to the skeletal system.

  • A network of blood vessels is present in both compact and spongy bones. 

  • The flexibility in both bones is because of the collagen fibers present in them.

  • The development of these bones occurs through the process called ossification.

  • The compact bone along with the spongy bone has to go through continuous remodeling.

  • Both these bones have the ability to heal in case of any fractures.

  • Both play an integral role in bone structure. Where one is present outside the bone, layering it, the other is within the bone. 

  • Together they (compact and spongy bone) work and support the body. Therefore facilitating movement and also skeletal integrity.


Conclusion

In the article above, you'll have access to all the necessary information related to compact vs spongy bone. While going through the article, you can learn the definition of compact and spongy bone. It'll help you understand the characteristics of compact and spongy bone. Alongside this, there's also a table explaining all the major differences between compact and spongy bone. So, go ahead and read the above article, to clear all your doubts related to compact vs spongy bone.

FAQs on Compact vs Spongy Bone: A Detailed Evaluation

1. What is the Main Function that a Compact Bone Performs?

A compact bone (cortical bone) helps to facilitate various functions. Among these, there is one main function that a compact bone performs. And that is forming the external layer of all the bones in the human body. Alongside this, these bones also surround the bone marrow and medullary cavity. Therefore, it helps in providing both strength and protection to the bones.

2. What's the Reason Behind Spongy Bone Being Called Cancellous?

Spongy bone is very similar in resemblance to a honeycomb or sponge therefore it is also called cancellous bone. The reason behind this is the spongy bone has many open spaces which connect together through flat places. These flat planes are called trabeculae and are made of bone. This trabeculae has three different types of bone cells within it. And they are namely- osteoclasts, osteoblasts, and osteocytes. Among them, the most useful cells are osteoblasts- they help in making new bones.

3. Is a Compact Bone Heavier than a Cancellous Bone?

Yes. Compact bone is heavier than a cancellous bone. It is because spongy or cancellous bone bone has lesser density than a compact bone. Similarly, spongy bone is also lighter when compared to the compact bone. The reason for cancellous bone to be unique than compact bone is the trabecular matrix present in it.