The Haversian system got its name from an English physician named Clopton Havers (1657-1702), who is known for his original research into the analysis of the microscopic structure of bones and joints. He was the first person to describe Charpy fibers.
Meaning of term
The Haversian system, or osteons, is the fundamental functional unit of a very compact bone. Osteons are roughly cylindrical structures that are typically a few millimeters long and about 0.2 mm in diameter. They are present in many bones of most mammals and some species of birds, reptiles and amphibians.
Histology of compact bone showing the Haversian system
Each system consists of concentric layers or plates of compact bone that surround a central canal. The Haversian canal contains the blood supply to the bone. The boundary of the osteon is the cement line.
Each Haversian channel is surrounded by a different number (5-20) concentricallyarranged plates of the bone matrix. Near the surface of the compact bones are parallel to the surface, they are called annular plates.
Some of the osteoblasts develop into osteocytes, each of which lives in its own little space or lacuna. Osteocytes come into contact with the cytoplasmic processes of their counterparts through a network of small transverse channels or tubules. This network facilitates the exchange of nutrients and metabolic waste.
Collagen fibers in a particular plate run parallel to each other, but the orientation of collagen fibers in other plates is oblique. The density of collagen fibers is lowest at the sutures between the lamellae, which explains the characteristic microscopic cross-sectional appearance of Haversian systems. The space between osteons is occupied by interstitial plates, which are the remnants of osteons.
The Haversian systems are connected to each other and to the periosteum by oblique canals called Volkmann's canals or perforating canals.
Drifting osteons
Drifting osteons are a phenomenon that is not fully understood. A drifting osteon is classified as a Haversian system that runs both longitudinally and transversely through the cortex. The osteon can "drift" in one direction or change direction several times, leaving a tail of lamella behind the advancing Haversian channel.
Investigative uses
In bioarchaeological research and forensicIn medical examinations, osteons in a bone fragment can be used to determine a person's sex and age, as well as aspects of taxonomy, diet, he alth, and motor history.
Osteons and their location vary by taxon, so genus and species can be differentiated using a bone fragment not otherwise identifiable. However, there is considerable variability between different skeletal bones, and features of some faunal osteons overlap with human osteons. Therefore, the study of Haversian systems is not the main application in the analysis of osteological remains. More research is needed, but osteohistology could have a positive impact on bioarchaeological, paleontological, and forensic research.
In recent decades, osteohistological studies of dinosaur fossils have been used to address a number of issues such as dinosaur growth frequency and whether it was the same across species, and whether dinosaurs were warm-blooded or not.
