Both the tonsils and adenoids are part of the Waldeyer ring, a circular structure of lymphoid tissue located in the nasopharynx and the oropharynx. It is formed by the following: the 2 palatine tonsils; the adenoids (or pharyngeal tonsils); the tubal (or Gelach) tonsils, which surround the eustachian tube openings; and the lingual tonsils, lymphoid tissue at the back of the base of tongue. The lymphoid tissue of the Waldeyer ring contains B-cell lymphocytes, T-cell lymphocytes, and a few mature plasma cells. This tissue is primarily involved in secretory immunity and regulates immunoglobulin production.
The cells within this tissue are organized into lymphoid follicles similar to lymph nodes, but have specialized endothelium-covered channels that facilitate direct antigen uptake. The independence of this system from lymphatic drainage is a unique advantage for antigen acquisition. The location and design of the Waldeyer ring allow for direct exposure of the immunologically active cells to foreign antigens entering the upper aerodigestive tract, which maximizes immunologic memory. These tissues are most active from the ages of 4 to 10 years and tend to involute after puberty. After their involution, the secretory immune function of these tissues remains, but at a lower level.
The palatine tonsils are the largest component of the Waldeyer ring and are found in the lateral walls of the oropharynx within a fossa formed by 3 pharyngeal muscles. The palatoglossus muscle forms the anterior tonsillar pillar, the palatopharyngeal muscle forms the posterior tonsillar pillar, and the pharyngeal constrictors, primarily the superior constrictor, form the base of the tonsillar fossa. The fibrous capsule, which surrounds each tonsil, is attached to the fascia of the pharyngeal muscles. The potential space between the tonsil and the pharyngeal muscles is the typical site for a peritonsillar abscess.
The glossopharyngeal nerve lies deep to the superior pharyngeal constrictor and supplies sensation to the tonsil through the tonsillar branch. The tympanic branch of the glossopharyngeal nerve is responsible for referred otalgia, which is commonly present with tonsillar inflammation or following tonsillar surgery. The descending branches of the lesser palatine nerve also supply sensation to the tonsil. The arterial supply of the inferior pole, the primary blood supply of the tonsil, is derived from the following arteries: the tonsillar branch of the dorsal lingual artery, the ascending branch of the palatine artery, and the tonsillar branch of the facial artery. The superior pole receives its blood supply from the ascending pharyngeal artery and from the lesser palatine artery. Venous drainage occurs via a venous peritonsillar plexus that drains into the lingual and pharyngeal veins, which eventually feed into the internal jugular vein. Efferent lymphatics drain to the tonsillar lymph node behind the angle of the mandible, to upper deep cervical lymph nodes, and to other jugulodigastric lymph nodes.
Tonsillar lymphoid tissue forms deep crypts that are lined with stratified antigen-processing squamous epithelium. These crypts maximize the ...