Adenoid

From Encyclopedia Jr, free information reference for Kids

Location of the adenoid

Adenoids are a mass of lymphoid tissue situated at the very back of the nose (the nasopharynx). These folds of lymphatic tissue are much like a mat of tiny lymph nodes. Adenoids are studded in the roof of a passage called the nasopharynx (where the nose blends into the mouth). Adenoids are sometimes called the nasopharyngeal tonsils. Normally, in children, they make a soft mound in the roof and posterior wall of the nasopharynx, just above and behind the uvula.

[edit] Function

Adenoids are part of the immune system. Like all lymphoid tissue, they trap infectious agents like viruses and bacteria, and they produce antibodies. Since the adenoids are located at the back of the nasal airway, they provide defense against inhaled substances. This function decreases with age as the adenoids shrink. Because adenoids do ordinarily shrink by late childhood, the problems caused by enlarged adenoids rarely occur in adults.

There is very little lymphoid tissue in the nasopharynx of young babies; humans are born without substantial adenoids. The mat of lymphoid tissue called adenoids starts to get sizable during the first year of life. Just how big the adenoids become is quite variable between individual children. Enlarged adenoids can become nearly the size of a ping pong ball and completely block airflow through the nasal passages. Even if enlarged adenoids are not substantial enough to physically block the back of the nose, they can obstruct airflow enough so that breathing through the nose requires an uncomfortable amount of work, and inhalation occurs instead through an open mouth. Adenoids can also obstruct the nasal airway enough to affect the voice without actually stopping nasal airflow altogether.

Nasal blockage is determined by least two factors: 1) the size of the adenoids, and 2) the size of the nasal pharynx passageway. The adenoid usually reaches is greatest size by about age 5 years or so, and then fades away ("atrophies") by late childhood - generally by the age of 7 years. The lymphoid tissue remains under the mucosa of the nasopharynx, and could be seen under a microscope if the area was biopsied, but the mass is so reduced in size that the roof of the nasopharynx becomes flat rather than mounded. Just as the size of the adenoids is variable between individuals, so is the age at which adenoids atrophy.

The adenoids, like all lymphoid tissue, enlarge when infected. Although lymphoid tissue does act to fight infection, sometimes bacteria and viruses can lodge within it and survive. Chronic infection, either viral or bacterial, can keep the pad of adenoids enlarged for years, even into adulthood. Some viruses, such as the Epstein-Barr Virus, can cause dramatic enlargement of lymphoid tissue. Primary or reactivation infections with Epstein Barr Virus, and certain other bacteria and viruses, can even cause enlargement of the adenoidal pad in an adult whose adenoids had previously become atrophied.

Adenoids are rarely visible on physical examination without the skilled use of mirrors or fiber optic endoscopes. A lateral X-ray view of the skull taken to show soft tissue density can show the adenoids, as can other imaging studies such as CT scans and MRI.

[edit] Symptoms of Enlarged or Infected Adenoids

The symptoms caused by enlarged adenoids are mostly due to where this lymphoid tissue is located. The adenoids are in the midline of the nasopharynx, and the Eustachian tubes open from either ear to the right and left of them. Eustachian tubes ventilate the middle ear. Very large adenoids will block air passage in both the nose and the ears. This obstruction of normal air ventilation can lead to both sinusitis and otitis media. In children with excessive middle ear infections and chronic middle ear fluid, there is a high bacterial count in the adenoids as compared to children without problematic otitis media, even if the size of the adenoids is small. The adenoids in these cases provides a reservoir of pathogenic bacteria that cause ear infections and subsequent middle ear effusions (fluid).

The nasopharynx lies right above the throat. Splashes of excessive "drip" from infected adenoids may land directly on the vocal cords. Although the larynx and vocal cords do not ordinarily become infected from adenoiditis, their mucosa does become irritated. The vocal cords are extremely sensitive to touch, and any fluid drops falling on them cause an irresistible urge to cough. Adenoiditis therefore is one of the causes of cough.

[edit] Removal of the Adenoids - Adenoidectomy

Surgical removal of the adenoids is a procedure called adenoidectomy. Carried out through the mouth under a general anaesthetic, adenoidectomy involves the adenoids being curetted, cauterised, lasered, or otherwise ablated. Adenoidectomy is most often performed because of nasal obstruction, but is also performed to reduce middle ear infections and fluid (otitis media). The procedure is often carried out at the same time as a tonsillectomy, since the adenoids can be clearly seen and assessed by the surgeon at that time. Adenoidectomy is also performed on patients who have chronic ear infections caused by the adenoids blocking the eustachian tube.

[edit] References

• Gates G (Mar 1996). "Sizing up the adenoid.". Arch Otolaryngol Head Neck Surg 122 (3): 239-40. PMID 8607949.
• Bluestone, Stool and Kenna (1996). Pediatric Otolaryngology (Volume II). WB Saunders Corporation, Chapters 58 and 59.
• BUPA Health Fact Sheet. "Adenoidectomy"
• US National Library of Medicine. "Enlarged Adenoids"

[edit] See also

• adenoidectomy
• lymphatic system
• pharynx
• tonsil
• "Adenoid Hynkel" is the dictator of Tomania in Charles Chaplin's The Great Dictator.