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.
Review Date 11/4/2018
Updated by: Josef Shargorodsky, MD, MPH, Johns Hopkins University School of Medicine, Baltimore, MD. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.