Organs and body parts: 3 recent additions

The Fabella is a bean-like bone tucked behind the knee that was thought to be lost to evolution. PHOTO: MICHAEL BERTHAUME/IMPERIAL COLLEGE LONDON
The mesentery was "promoted" to become the body's 79th organ in 2016. PHOTO: UNIVERSITY HOSPITAL GROUP
The interstitium is a network of fluid-filled spaces found under the skin and between organs. PHOTO: MOUNT SINAI HEALTH SYSTEM

Mesentery (2016)

Known for over a century as a fragmented structure made of separate parts, the mesentery - connective tissues that link the stomach and intestines to the abdomen - was "promoted" to become the body's 79th organ in 2016.

All abdominal digestive organs develop within the folds of the mesentery.

The organ carries blood and lymphatic fluid between the intestine and the rest of the body.

The interstitium (2018)

It is a network of fluid-filled spaces found under the skin and between organs.

The mesh-like structure was made visible when scientists used a laser-equipped mini-microscope to examine a bile duct.

The ubiquitous structure may play a role in helping cancer cells spread around the body, said the researchers who discovered it.

But scientists are torn on whether to call it an organ.

The fabella (2019)

A bean-like bone tucked behind the knee was thought to be lost to evolution, but it is making a return.

Almost 40 per cent of the world's population is estimated to have that bone, compared to 11 per cent 100 years ago.

The reason for that extra bone is improved nutrition. Good food is making the average person taller and heavier than his ancestors, putting more pressure on his knee. The force causes the fabella to grow.

But the presence of the bone has also been associated with several knee ailments.

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