The palatine tonsils are dense compact bodies of lymphoid tissue that are located in the lateral wall of the oropharynx, bounded by the palatoglossus muscle anteriorly and the palatopharyngeus and superior constrictor muscles posteriorly and laterally.
The adenoid is a median mass of mucosa-associated lymphoid tissue. It is situated in the roof and posterior wall of the nasopharynx.
The adenoid was first described in 1868 by the Danish physician Meyer in his paper “Adenoid Vegetations in the Nasopharyngeal Cavity.”
Both tonsils and adenoid are part of the Waldeyer ring, which is a ring of lymphoid tissue found in the pharynx. The lymphoid tissue in this ring provides defense against pathogens. The Waldeyer ring is involved in the production of immunoglobulins and the development of both B cells and T cells.