THE ARRANGEMENTE OF BONE LAMELLAE IN COMPACT AND SPONGY BONES.
THE HAVERSIAN SYSTEMS OR OSTEONS – 1
THE HAVERSIAN SYSTEMS OR OSTEONS – 1
The Haversian systems or osteons are found concentrated in the compact type of bone, a dense tissue that forms the hard outer covering of bones.
The spongy bone that occupies the bone interior, on the other hand, is differently sytructured. It does not have Haversian systems as its trabeculae are formed by stacks 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 spongy bone that occupies the bone interior, on the other hand, is differently sytructured. It does not have Haversian systems as its trabeculae are formed by stacks 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 parallel collagen fibers forming lamellae and the osteocyes interposed between lamellae. Observe how the collagen fibers change their direction from one lamella to the other. This type of arrangement provides the bones with great resistance against mechanical forces and torsion.
