  Background and Objective: Mammalian compact bone is composed mostly of
Haversian system. Although there are many studies describing the typical
Haversian system in mammals, there are few studies conducted on bones from
non-mammalian species. The objective of the current study was to investigate
the existence of the typical Haversian system in compact bones from reptiles
and birds. Materials and Methods: Femora were collected from geckos, Nile
monitors, sparrows, ducks and geese. Samples were then, fixed in 10%
paraformaldehyde and embedded in paraffin. Paraffin sections were stained with
hematoxylin and eosin or Von Kossa and then examined using light microscopy.
Results: The current study showed different histological structures of compact
bones from studied species and an absence of the typical Haversian system seen
in mammals. The compact bone of geckos was mostly avascular, while Nile monitor
bone was highly vascular. Sparrow bone showed one side vascular and the other
side avascular. The vascularity was represented by primary vascular canals
surrounded by a few irregularly arranged osteocytes inside their lacunae
forming primary osteons. Bone tissue from ducks and geese were similar and were
composed mostly of dense Haversian tissue, while some areas had primary
osteons. Conclusion: The compact bone microstructure in some reptile and bird
species lack the typical Haversian system described in mammals. This will be of
a great importance in developing a better understanding of long bone anatomy
and physiology in different species.
