Vestigial organs can be defined as an organ that once was useful in an animal's evolutionary past, but that now is useless or very close to useless. As vermiform appendix plays no significant function in humans, so it is considered as a vestigial organ.

The vestigial part of the human alimentary canal is the Vermiform appendix.

Explanation:

The alimentary canal, also known as the digestive tract, is a long tube that runs from the mouth to the anus. It is responsible for the digestion and absorption of food. Throughout the course of evolution, certain parts of the alimentary canal have become reduced or lost their original function, resulting in vestigial organs.

The Vermiform appendix is a small, finger-like projection located at the beginning of the large intestine, specifically at the junction of the small intestine and the large intestine. It is named "vermiform" due to its worm-like appearance.

The Vermiform appendix is considered vestigial because it no longer performs a significant role in the human digestive system. In the past, it was believed to be a vestige of a larger, more functional organ related to digestion. However, recent research suggests that the appendix may have some immunological functions, particularly in the development and maintenance of gut-associated lymphoid tissue. Despite this, its overall contribution to digestion and immunity is considered minimal.

The Vermiform appendix is prone to inflammation, a condition known as appendicitis, which can be a medical emergency requiring surgical removal. The removal of the appendix does not result in any major digestive or immune system dysfunction, further supporting its vestigial nature.

In conclusion, the Vermiform appendix is considered a vestigial part of the human alimentary canal because it has lost its original function related to digestion and plays a minimal role in immunity.