The large intestine
The large intestine is about 1.5 m long. It begins at the caecum and ends at the anus; its last, wider part is the rectum.
What enters it contains few nutrients — mostly water and undigested compounds such as cellulose. Its job is to absorb water from this liquid, turning it semi-solid.
In the rectum this material is faeces: semi-solid, yellowish from bile pigments, and made of undigested matter, microorganisms, epithelial cells shed from the gut wall, and mucus. When the rectum is full, faeces leave through the anus.
Appendicitis
A small closed tube, the appendix, hangs from the end of the caecum. In humans it is small, and it can become infected and swollen. This condition is appendicitis.