Difference Between Spongy Bone vs. Compact Bone

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Main Difference

The spongy bone and compact bone are classified as two different types of bones, but it is nothing more than a misconception as they are two of the different parts of the similar bone. Both these different parts are different regarding the structure, porosity, and the tissues. The compact bone is made up of the cortical tissues, whereas the spongy bone is made up of the cancellous tissues. The compact bone has the less porosity and gives the solid and smooth white appearance to the bone. Contrary to this, the inner side bones (spongy bones) are porous and have shapes of rods and plates.

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Comparison Chart

Spongy BoneCompact Bone
AreaMakes up the inner cavity of the bone.Outer covering.
PorosityMoreLess
Also Known AsCancellous tissueCortical Tissue
Functional UnitTrabeculaeOsteons

What is Spongy Bone?

The spongy bone is the soft inner side of the bone; it is composed up of the cancellous tissues. Even with having the surface area ten times more than the compact bones, spongy bones only makes up the 20 percent of the entire mass of the bones in the body. They have rod and plates shape with having more numbers of pores as compared to the compact bones. The bone part is either classified as the spongy or the compact by the proportions of minerals it possesses along with the nature of the tissues. Unlike, compact bone, the Haversian system is absent in the case of spongy tissues. They are equally vital as the other type of the bone as they form the inner part of the bone, where the porosity is needed, and the elasticity to some extent is also necessarily required. The spongy bones are situated at the head parts of the long bones. The reason behind their lesser weight even with having the maximum surface are coverage is that they are made of the trabeculae, which are the thin thread-like structures. Regarding mass, the trabeculae have quite the less mass relatively to the osteons, which makes up the compact bones. Informally, the spongy bone is often termed as the inner bone as it constitutes that specific part of the bone. It is also the part where the red bone marrow gets stored after it is developed. As the calcium availability to the spongy bone is not that exclusive, such bones can also suffer due to the severe bone diseases like osteoporosis.

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What is Compact Bone?

The compact bones are the well-structured bones that make up the outer area of the bone; they are also known as the cortical bones and works as the protective layer around the internal cavity of the bone. Around every of the bone in the human body have this type of the bone tissues as they give the whitish appearance along with the solidity and smoothness. As these bones comprise the outer part of the bones, they are well-structured and have very fewer pores in them. The less porosity is more of the requirement in these types of the bones. Therefore, they are also called the dense bone (due to their less porosity). Even though the compact bone tissues have ten times lesser surface area as compared to the spongy bones, they make around 80 percent of the whole bone mass of the body. These bones are made up of the osteon which is a heavier functional unit as compared to the trabeculae, which makes up the spongy bones. Most commonly, these compact bones are situated in the shaft of the long bones like the femur. The point which makes these bones strong is that they have negligible gaps which made them bounded together and counted for the hardness of that bone.

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Spongy Bone vs. Compact Bone

  • The compact bones make up the outer area of the bone, which works as covering to the internal cavity. On the other hand, the spongy bones make up the internal area of the bone.
  • The compact bones are known as the dense bones as they have less porosity, whereas the spongy bones have more porosity as compared to them.
  • The spongy bone is also called the cancellous tissue while the compact bone is called the cortical tissue.
  • The spongy bones comprise of the trabeculae, whereas the compact bones comprise of the osteons.

Comparison Video