Appendix

This is a photomicrograph of the human appendix.

The arrangement of the layers in its walls is similar to that seen elsewhere in the large intestine. However, the outer layer of muscle fibres in the muscularis externa forms a continuous layer.

The most characteristic property of the appendix is the presence of masses of lymphoid tissue in the mucosa and submucosa. There are often follicles containing paler germinal centres similar to the follicles of Peyers patches in the small intestine.

Can you identify the layers (epithelium, mucosa, submucosa, muscularis externa) and the aggregations of lymphoid tissue?