HAVERSIAN SYSTEMS OR OSTEONS – 1
The Haversian Systems is found in the compact bone, a dense tissue that forms the hard outer covering of bones.
The structure of the mature spongy bone, on the other hand, is very different. It does not have Haversian Systems. The spóngy bone is formed by trabeculae made of parallel bone lamellae.
Haversian systems measure around 0.2–0.4 mm in diameter and a few millimeters long.
Its osteocytes are placed between the concentric bone lamellae.
Each Haversian system has a central tunnel, called Haversian canal or osteonal canal. This tunnel is occupied by blood vessels and nerves. The presence of lymphatic vessels within the canals is still subject to discussion.
The surface of the Haversian canal is lined with osteoblasts, as any other inner bone surface.
The structure of the mature spongy bone, on the other hand, is very different. It does not have Haversian Systems. The spóngy bone is formed by trabeculae made of parallel bone lamellae.
Haversian systems measure around 0.2–0.4 mm in diameter and a few millimeters long.
Its osteocytes are placed between the concentric bone lamellae.
Each Haversian system has a central tunnel, called Haversian canal or osteonal canal. This tunnel is occupied by blood vessels and nerves. The presence of lymphatic vessels within the canals is still subject to discussion.
The surface of the Haversian canal is lined with osteoblasts, as any other inner bone surface.
Top image
Schematic drawing of a Haversian system formed by three round lamellae.
Bottom image
Notice the arrangement of collagen fibers in parallel forming lamellae with osteocyes interposed between lamellae. Observe how the collagen fibers of change their direction from one lamella to the other. This type of arrangement provides the bones with great resistance toward mechanical forces and torsion.
