Lymph nodes are small bean shaped structures lying along the course of the lymphatics . Lymph nodes have two main functions:

  As phagocytic cells, which act as filters for particulate matter and micro-organisms.
  Presentation of antigens to the immune system.

The tonsils are located at the back of the mouth and adenoids at the back of the nasal cavity. Both consist of lymph tissue and help to fight off infection. They are at their largest during childhood and gradually shrink with age.

Peyer's Patch

These are quite large aggregates of lymphoid tissue found in the small intestine, part of the lymphatic system which help to fight infection.