Adenoids are a mass of lymphoid tissue situated posterior to the nasal cavity, in the roof of the nasopharynx

Nasopharynx

The nasopharynx is the uppermost part of the pharynx. It extends from the base of the skull to the upper surface of the soft palate; it differs from the oral and laryngeal parts of the pharynx in that its cavity always remains patent .-Lateral:On its lateral wall is the pharyngeal ostium of the...

, where the nose

Human nose

The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...

 blends into the throat

Throat

In vertebrate anatomy, the throat is the anterior part of the neck, in front of the vertebral column. It consists of the pharynx and larynx...

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Normally, in child

Child

Biologically, a child is generally a human between the stages of birth and puberty. Some vernacular definitions of a child include the fetus, as being an unborn child. The legal definition of "child" generally refers to a minor, otherwise known as a person younger than the age of majority...

ren, they make a soft mound in the roof and posterior wall of the nasopharynx

Nasopharynx

The nasopharynx is the uppermost part of the pharynx. It extends from the base of the skull to the upper surface of the soft palate; it differs from the oral and laryngeal parts of the pharynx in that its cavity always remains patent .-Lateral:On its lateral wall is the pharyngeal ostium of the...

, just above and behind the uvula.
Adenoids, unlike other types of tonsil

Tonsil

Palatine tonsils, occasionally called the faucial tonsils, are the tonsils that can be seen on the left and right sides at the back of the throat....

s, have pseudostratified columnar ciliated epithelium

Pseudostratified epithelium

A pseudostratified epithelium is a type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelia...

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They also differ from the other tonsil types by lacking crypts

Crypt (anatomy)

Crypts are anatomical structures that are narrow but deep invaginations into a larger structure.One common type of anatomical crypt is the Crypts of Lieberkühn. However, it is not the only type: some types of tonsils also have crypts...

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The adenoids are often removed along with the tonsils.