Certified Tumor Registrar (CTR) Practice Exam

Peyer patches are specialized lymphoid tissue found in the gastrointestinal tract, specifically in the small intestine. They play a crucial role in the immune response by helping to monitor intestinal bacteria and prevent the growth of pathogenic bacteria in the intestines. This collection of lymphoid follicles is essential for the development of immune tolerance and the regulation of gut immunity.

The location of Peyer patches in the small intestine allows them to interact with the gut flora and facilitate a localized immune response. This is vital for maintaining the balance between a robust immune response to pathogens while also tolerating non-harmful antigens.

The other organs listed do not contain Peyer patches; the bladder, brain, and kidneys have different structures and functions related to their specific roles in the body. Therefore, the correct association of Peyer patches with the small intestine highlights their integral function in intestinal immunity.