The structure of blood vessel walls is important in the regulation
of blood flow. The middle layer (tunica media) contains smooth
muscle cellsthat relax or contract to either widen or narrow the
size of the artery.
Review Date: 08/17/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
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