A Rough look at the tonsils and adenoids, for Bonny Peppa!

Lymphoid organs include: adenoids (two glands located at the back of the

nasal passage)

appendix (a small tube that is connected to the large intestine)

blood vessels (the arteries, veins, and capillaries through which blood flows)

bone marrow (the soft, fatty tissue found in bone cavities)

lymph nodes (small organs shaped like beans, which are located throughout the body and connect via the lymphatic vessels)

lymphatic vessels (a network of channels throughout the body that carries lymphocytes to the lymphoid organs and bloodstream)

Peyer's patches (lymphoid tissue in the small intestine)

spleen (a fist-sized organ located in the abdominal cavity)

thymus (two lobes that join in front of the trachea behind the breast bone)

tonsils (two oval masses in the back of the throat)

Lymphoid Organs

• Tonsils: 3 sets

Fig. 14.3

Lymphoid Organs

• Thymus: atrophies with age

• Spleen: can live without this

Figure 20.8

Other Lymphoid Organs

• Include:– Tonsils– Thymus– Spleen – Peyer’s Patches– Appendix– Bone Marrow-Stem cells– All contain reticular CT and

lymphocytes, but none of them actively filter lymph

– These other lymphoid organs contain efferent but no afferent lymphatic vessels.

largest

• So we see the tonsils and adenoids are lymphoid organs

• They have a PROTECTIVE FUNCTION

TonsilsTonsils

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Small masses of lymphoid tissue around the pharynx

• Trap and remove bacteria and other foreign materials

• Tonsillitis is caused by congestion with bacteria

• Tonsils • The tonsils are accumulations of lymphoid tissue

located in a protective ring - called Waldeyer's ring - under mucous membranes in the mouth and back of the throat surrounding the openings of the digestive and respiratory tracts.

• Help protect against bacteria that may invade tissues in the area around the openings between the oral and nasal cavities.

• The tonsils serve as the first line of defense from the exterior and as such are subject to chronic infection.-tonsillitis.

• Depending on their localisation we distinguish between palatine, pharyngeal (adenoids) or lingual tonsils.

Tonsils• Form a ring of lymphoid

tissue around the entrance to the pharynx

• 3 main sets:– Palatine

• Located on either side of the posterior oral cavity

• Largest and infected most often

– Lingual• Lie at the base of the

tongue– Pharyngeal

• Found in the posterior wall of the nasopharynx

• Called adenoids when infected

Tonsils• Contain multiple lymphoid follicles overlain by epithelial crypts

• Crypts trap bacteria which work their way into the lymphoid tissue where they are destroyed– Why is this a

risky method of fighting pathogens?

– What advantage does this method confer?

Tonsils• Incompletely encapsulated lymphoid nodules• Simple lymphoid organs /“Lymph nodules” in Simple lymphoid organs /“Lymph nodules” in

the mouth/pharynxthe mouth/pharynx • Palatine or adenoids: covered by stratified

squamous nonkeratinized epithelium; crypts; underlying connective tissue barrier, lateral to the pharynx

• Pharyngeal: covered by ciliated pseudostratified epithelium, no crypts

• Lingual: smaller, at base of tongue posteriorly; covered by stratified squamous nonkeratinized epithelium; one crypt in each nodule

Palatine tonsils--located on each side of the throat.

•

• The Palatine tonsils • are those which we loosely refer to as “the

tonsils” in laymens terms and every day speech.

• are located in the lateral wall of the oropharynx and covered by a stratified squamous epithelium

• contains T and B cells and antigen presenting cells

• are deep crypts• are large masses of lymphoid tissue

• When we speak of the “tonsils” in Barbados we mean the Palatine tonsil

• When we speak of the “adenoids” in Barbados we mean the Pharyngeal tonsil

• Note that they have a different location!

• The pharyngeal tonsils (also called nasopharyngeal tonsils or adenoids)

• are located in the upper posterior part of the throat (nasopharynx) and

• covered by a pseudostratified ciliated epithelium with goblet cells.

Lingual tonsils are situated in the lamina propria at near the base of the tongue. They are covered by a stratified

squamous epithelium.

• The tonsils do not have afferent lymph vessels but efferent lymph vessels are present.

• Exposure to antigens relies on the contact of antigens with cells of the immune system across the epithelium which covers the tonsils.

• The epithelium of the palatine and lingual tonsils forms deep crypts into the lymphoid tissue, and the resulting increase of the surface area is one way to facilitate the contact of antigens with the immune cells.

• In addition, the epithelium may specialise in places to form an open meshwork of cells with an incomplete basal lamina (a reticulated epithelium) which allows the infiltration of the epithelium by lymphocytes and macrophages.

• Tonsillar lymphoid nodules consist mainly of B-lymphocytes.

Other areas are occupied by T-lymphocytes, activated B-lymphocytes and other cells of the immune system.

The tonsils share some histological features with lymph nodes:

• cells in the tonsils are supported by a fine network of reticular fibres and

• high-endothelial (postcapillary) venules function in the "homing" of circulating lymphocytes - this is actually a shared feature of all lymphoid tissues and organs.

• The palatine tonsils are surrounded by a thick hemicapsule of connective tissue, which delimits them from the pharyngeal muscle and facilitates their removal in tonsillitis.