Mucosa-associated Lymphoid Tissue (MALT)

Examine a section of tonsil (slide 136, Fig. 14-15). Identify the stratified squamous epithelium covering the tonsil and the dense connective tissue at its base. Identify the large lymphoid follicles. The large, pale cells scattered among the lymphocytes in the follicles are macrophages acting as antigen-presenting cells.

Why might you expect there to lots of APCs in tonsils?

Clinical note: Tonsillitis, pharyngitis, and other upper respiratory tract infections are among the most common problems involving the head and neck. Tonsillectomies, which were formerly much more common than now, may be required if chronic tonsillitis causes enlargement of the affected structures to the degree that air passages are obstructed. To the right we see a pair of very large and inflamed tonsils.

Examine the connective tissue in the wall of the ileum (slides 27 and 37) and identify the nodule of lymphoid tissue representing a Peyer's patch (Fig. 14-16). Similar diffuse nodules of various sizes will be seen in sections of esophagus and many regions of the small and large intestines.

What is one difference between the lymphoid tissue of tonsils and Peyer’s patches?

Identify the nodules of lymphoid tissue in the wall of the appendix (slide 41, Fig. 15-39).

What are some distinguishing features of the appendix?

What is the general purpose of MALT along the gut?

The spleen is next.