Sternum
From EvoWiki
The sternum is the breast bone. It is present in most modern terrestrial vertebrates, except for turtles and snakes. It may be comprised entirely of cartilage, or (at least partially) ossified (i.e. replaced with bone).
It consists of three parts (listed from cranial to caudal)
Morphology
In amphibians, the sternum is a small bone, lying ventrally between the left and right pectoral girdles, just cranial to the coracoids. In amniotes, the sternum is attached to the majority of the trunk ribs via cartilages, where it serves as a muscle attachment site and unites the ribcage, enhancing lung ventilation.
In birds, the sternum features a keel-shaped carina, providing a broad origin for the large wing adductor muscles (such as M. pectoralis major) used in flight. This feature has been lost, along the evolution of flightlessness, in ratites.
References
- Liem K.F, Bemis W.E, Walker W.F Jr, and Grande L. (2001), Functional anatomy of the vertebrates : an evolutionary perspective, Harcourt College Publishers, Third Edition, pp 275-6, 285
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This page is part of the EvoWiki Encyclopedia of Anatomy and Physiology. |
