Adenoids are masses of tissue located high on the posterior wall of the pharynx. They are made up of lymphatic tissue, which trap and destroy pathogens in the air that enter the nasopharynx.
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.