Flat bones are made up of a layer of spongy bone between two thin layers of compact bone. They have a flat shape, not rounded. Examples include the skull and rib bones. Flat bones have marrow, but they do not have a bone marrow cavity.
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Review Date 9/16/2019
Updated by: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.