Skeletons - Research Article from Macmillan Science Library: Animal Sciences

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Bony Skeleton

Vertebrata (vertebrates) is an animal group that includes fishes, amphibians, reptiles, and mammals. The vertebrate skeleton is an internal collection of relatively rigid structures joined by more flexible regions. The hard components of the skeleton are made up of bone, cartilage, or a combination of these two connective tissues.

Vertebrates are closely related to a number of less-familiar aquatic organisms, such as tunicates, sea squirts, and lancelets (Amphioxus). These animals have a skeleton composed entirely of a cartilaginous rod called a notochord. The notochord is somewhat flexible and runs along the back of the animal.

In all vertebrates, the framework first laid down during development is cartilaginous. As development proceeds, most of the cartilage is replaced by calcified bone through the action of bone precursor cells called osteoblasts. This process is called ossification. During ossification, some bones fuse together, reducing the total number of bony elements. At...

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This section contains 1,288 words
(approx. 5 pages at 300 words per page)
Buy the Skeletons Encyclopedia Article
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Macmillan Science Library: Animal Sciences
Skeletons from Macmillan Science Library: Animal Sciences. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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