The gastrointestinal, respiratory, and genitourinary tracts contain collections of non-encapsulated lymphoid tissue (diffuse lymphoid tissue and nodules), which is strategically located to protect the body against pathogens. One such example is the Peyer's patch in the gastrointestinal tract.

• Examine the connective tissue in the wall of the ileum (sample 1, sample 2). Identify the abundance of lymphocytes in the loose connective tissue of the villi and the collection of lymphoid nodules representing a Peyer's patch (see image below). Similar collections of lymphocytes and diffuse nodules of various sizes will be seen in sections of esophagus and many regions of the small and large intestines (see image below).

• Identify nodules of lymphoid tissue in these two specimens of the appendix and appendix sample two.
   

The spleen is next.