The definition of an organ is contested, but generally, it must be self-contained and provide an essential function to the body.

This strangely vague definition has created more than one controversy as scientists dive deeper into the body.

While screening 100 patients for prostate and urethral gland cancer, the team discovered two new salivary glands near the back of the nasal cavity. They also found them in two cadavers.

The glands only became apparent because the scientists used an advanced type of scanning used to screen for cancers. They wouldn't have appeared using traditional CT or MRI scanning.

Sparing these spit glands during radiation might alleviate uncomfortable feelings of dry mouth or difficulty swallowing, the scientists argue.

They argued that there's a thin layer of connective tissue that winds its way under the skin and around all our other crucial organs in the body. That tissue is filled with tiny, fluid-filled niches.

They called the organ the interstitium.

These findings were controversial. Anirban Maitra a pathologist at the University of Texas Medical Center, told The Scientist ...

For centuries, scientists classified the mesentery – structure that anchors the intestines in place – as a tissue, not an organ.

In 2016, scientists in Ireland found that the mesentery was actually one continuous chain — not many disconnected pieces — when they examined cadavers and people undergoing surgery.