Lymphoid tissue: Tonsils

What are Tonsils?

This is a low power photograph of a tonsil. Can you identify the lymphoid follicles with pale germinal centres, part of a blind crypt, and the hemi-capsule?

Tonsils are large non-encapsulated (or partially encapsulated) masses of lymphoid tissue, that lie in the walls of the pharynx and nasopharynx and at the base of the tongue.
The luminal surface of the tonsils are covered with a stratified squamous epithelium (in common with the oral epithelia).

The tonsils have many invaginations which form blind crypts.

Below the epithelium, there are many lymphoid follicles beneath which have germinal centres like the lymph nodes.
The epithelial cells are able to phagocytose bacteria, and transfer them to macrophages, which then present the foreign antigens to B-cells, which are activated (with the help of T cells). Again, like the MALT, the activated cells mostly secrete IgA type antibodies, which are secreted locally.

You should note that these partially encapsulated tonsils/lymphoid aggregations are not involved in filtering lymph.

This is part of the tonsil at a higher magnification. Can you identify the stratified squamous epithelium lining the blind crypt?