The appendix is missing the taeniae coli and appendices epiploicae layers.
While the appendix shares many histological features with the colon, two key structures present in the colon are absent in the appendix.
Absence of Taeniae Coli and Appendices Epiploicae
- Taeniae Coli: The taeniae coli are three distinct longitudinal bands of smooth muscle that run along the surface of the colon. These bands are responsible for the characteristic haustrations (pouches) of the colon. The appendix lacks these distinct bands; instead, its longitudinal muscle layer is more uniform.
- Appendices Epiploicae: These are small, fat-filled pouches that are attached to the serosa of the colon. The appendix does not have appendices epiploicae.
Layers Present in the Appendix
The appendix still retains the following layers, similar to the colon:
- Mucosa: The innermost layer, consisting of epithelium, lamina propria, and muscularis mucosae. The appendix mucosa is rich in lymphoid follicles.
- Submucosa: A layer of connective tissue containing blood vessels, nerves, and lymphatics.
- Muscularis Externa: Consisting of an inner circular layer and an outer longitudinal layer (although the outer longitudinal layer is not organized into taeniae coli).
- Serosa: The outermost layer, a serous membrane that covers the appendix.
