Compact Bone

Compact Bone

Compact bone or cortical bone is an osseous tissue, one of the two that are found in body (the other is Spongy bone), which makes bones. Cortical bone, as the name suggests, forms the outer shell or the cortex of bones and gives the outer layer a smooth appearance. It is hard and stiff and contributes to 80% of the weight of the skeleton. Moreover, it has larger mass as compared to the spongy bone. Some of the common differences are as discussed below.

Compact Bone and Spongy Bone

Compact Bone

To start with, compact bone is strong and dense and forms the exterior part of the bone while Spongy bone, as the name indicates, is porous and weaker compared to Compact bone and is located on the bone’s inner part. Compact bone has very little porosity and for the same reason it is called the dense bone. 20% of the bone mass is due to the Spongy bone while the rest 80% is constitutes by the Compact bone but the surface area of Spongy area is ten times more. Another point of difference is that the tissues of the Spongy bone are surrounded by blood but the compact bone ones are bordered by marrow.


  • Compact bone provides protection to the Cancellous or Spongy bone by wrapping it and forming a strong exterior.
  • Compact bone supports the human skeleton – it gives it 80% of the weight it has.  Spongy bone is soft and porous and cannot support the human skeleton without the help of Compact bone.
  • It is the main constituent of the bones in the leg – it gives them strength and rigidity.
  • Compact bone tissues with Osteons and Haversian dispose waste and deposits of minerals which builds strength.
  • Immature cortical bones don’t contain Osteons – they form framework of collagen fiber and it is replaced by new mature bones that make Osteon.
  • Compact bones in the skull give it proper balance and provide it ability to withstand traumas.

Microscopic Structure

Compact bones are filled with inorganic sounds and the tiny spaces contain Osetocytes or the bone cells. Human skeleton is made up of mostly the Compact bones and the rest of the skeleton constitutes Cancellous Bone which has a sponge like appearance. Both of the bones are found in human body; they are distinguished depending upon the soft tissues proportions.

Compact bones are found in legs, arms, fingers and toes – they provide extra support to the body. The short bones, on the other hand, are cube-shaped and are found in wrists and ankles.


Some of the commonly occurring disorders of Compact bones include Ostroporosis, Osteomyelitis infection and congenital musculoskeletal defects. Regular intake of calcium and minerals is a necessity for this bone. Also, Vitamin D and K are also very important for Compact bone and lack of these in the diet can cause changes the structure of the bone and affects its function. Aging also weakens the bones and due to the aging process, bones can get fractured.

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