Adenoids
Adenoids
Adenoids
Introduction
The adenoids exist as a rectangular mass of lymphatic tissue in the
nasopharynx.
The adenoids are midline structures situated on the roof and posterior wall
of the nasopharynx.
They form part of the Waldeyer ring, whose components include the
adenoids, the palatine tonsils, and the lingual tonsils.
Adenoid tissue can be found extending to the eustachian tube opening and
the fossa of Rosenmuller.
Adenoids with other lymphatic tissue in the nasopharynx are the first line of
defense against ingested or inhaled pathogens.
Histologically, the lymphoid tissue of the adenoids divides into four lobes
with seromucous glands interposed throughout the substance of the tissue.
Adenoids, in conjunction with the lingual and palatine tonsils, are involved
in the development of T cells and B cells.
On the surface, adenoid tissue has specialized antigen-capture cells, M
cells, which uptake the pathogenic antigens and then alert the underlying B
cells.
Recent scientific literature has provided some evidence that adenoids also
produce T lymphocytes like the thymus gland.
The adenoids can function as a bacterial reservoir for the nasal cavity and
are implicated in the pathogenesis of chronic rhinosinusitis.
The fusion of two lateral primordia forms the adenoids during embryological
development.
Nerve Supply
The nervous supply to the adenoids is via the pharyngeal plexus.
The pharyngeal plexus contains fibers of cranial nerves IX, X, and XI. The
innervation of the adenoids originates from the vagus and the
glossopharyngeal nerves.
Muscles
The muscles found in the nasopharynx include the levator palatini and the
pharyngeal constrictors.
Physiologic Variants
Adenoids decrease in size with age, typically atrophying completely by the
teenage years.
This variant can occur through two means: by a fissure extending from the
pharyngeal bursa or by a median fold passing towards the nasal septum
from the pharyngeal bursa.
Surgical Considerations
Adenoidectomy: An adenoidectomy is the surgical excision of adenoid
tissue.
Clinical Significance
Adenoid hypertrophy: Impaired mucociliary clearance has been implicated
as playing a role in adenoid hypertrophy, a condition typically seen in
children.
Adenoiditis:
Adenoiditis refers to inflammation of adenoid tissue secondary to an
infection.
Common pathogens leading to adenoiditis are often the same as those
implicated in rhinosinusitis and include Streptococcus pneumoniae,
Hemophilus influenza, and Moraxella catharrhalis.
Reference
Mnatsakanian, Ani, et al. “Anatomy, Head and Neck,
Adenoids.” StatPearls, StatPearls Publishing, 2020. PubMed,
http://www.ncbi.nlm.nih.gov/books/NBK538137/.