Difference between Compact and Trabecular Bone

Bones are specialised forms of connective tissues comprising cells and extracellular matrix.

There are different types of bones:

  • Lamellated bones – Cancellous (also called trabecular or spongy bone), Compact
  • Course fibered bones – formed at the time of bone-healing, seen in embryo
  • Bundle bones – comprises Sharpey’s fibres

The traits of all the bones are a dense outer sheet of the compact bones and a medullary cavity (central). The cavity in living bones is filled with yellow or red bone marrow, which is specifically interrupted at the extremities of long bones by a mesh of bone trabeculae.

Compact bone

  • It comprises closely packed osteons or Haversian systems. The osteons instead comprise an osteonic canal (central canal), wrapped by concentric rings of the matrix. It is between these rings that the osteocytes are seen in the lacunae
  • Canaliculi (small channels) give out from the lacunae to the osteonic canal rendering a route through the stiff matrix
  • The osteonic systems in these are densely packed, imparting its solid-mass like appearance
  • These bones are denser compared to cancellous bones; their spaces are reduced in size

Trabecular bone

  • These bones are also called spongy bones or cancellous bones and are porous, light wrapping several large spaces providing the characteristic spongy or honeycombed appearance
  • The matrix of bone is arranged into a 3D latticework of bony processes, such as trabeculae organised through the lines of stress. The arrangement provides maximum strength, like the braces used in supporting a building
  • Often, the spaces between are filled with blood vessels and marrow
  • The canaliculi link to the adjacent cavities rather than a central Haversian canal receiving its blood supply
  • These bones account for 20% of the human skeleton, rendering structural assistance and flexibility with no weight of the compact bone

Key Differences between Compact and Trabecular Bone

The table below depicts the differences between Compact bone and Trabecular bone.

Compact Bone

Trabecular Bone

What are they also referred to as?

Cortical bone

Cancellous or spongy bones

What are they?

The denser matter used in creating much of the tough structure of the skeleton

These are extremely vascularised, porous bones

What do they make up?

Outer covering of bones

Inner cavities of bones

Shape

Cylindrical

Cuboidal

Space between lamellae

Absent

Present

Functional units

Osteons

Trabecula

Marrow cavity

Present

Absent

Colour of bone marrow

Yellow

Red

What does it constitute?

Shaft of long bones

Terminals of long bones

Calcium content

High

Low

What percentage of it constitutes the weight of the skeleton

80%

20%

Function

Involved in providing structural assistance to the body

Serves as a buffer for the compact bones

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