Flat bones are made up of a layer of spongy bone between two thin layers of compact bone. Their shape is flattened, not rounded. Examples include the skull and ribs. Flat bones have marrow, but not a bone marrow cavity.
Silverstein JA, Moeller JL, Hutchinson MR. Common issues in orthopedics. In: Anderson GJ, Hensrud DD. In: Rakel RE, Rakel DP eds. Textbook of Family Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 30.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.