For more than a century, a tiny structure has been sitting beside the ovary, largely ignored by modern medicine (another loss we can attribute to medical misogyny). It appeared in early editions of Gray’s Anatomy, but gradually vanished from textbooks as scientists came to regard it as little more than an evolutionary leftover. But now, researchers are taking another look – and what they’re finding suggests this forgotten piece of anatomy may be doing far more for women's health than previously thought.
Here's what to know...
What exactly is the rete ovarii?
It’s called the rete ovarii, or RO – from the Latin word for “network” – and it’s a small structure made up of interconnected tubes and channels attached directly to the ovary.
Interestingly, there’s a male equivalent called the rete testis, which has a well-established job helping transport sperm. The rete ovarii, however, was never given such a clear purpose. Without an obvious function, it became easy to dismiss and, eventually, easy to forget.
Why are scientists suddenly interested in it?
A 2025 study brought the rete ovarii back into focus by looking at it with technology earlier anatomists simply didn’t have.
Researchers at Duke University Medical Centre studied the structure in mice using advanced microscopy that allowed them to examine entire ovaries rather than relying on thin tissue slices. They discovered that the rete ovarii has three distinct regions that remain present into adulthood, including hollow tubes that appear capable of moving fluid and cellular material towards the ovary.
In other words: the organ doesn’t look quite as redundant as once assumed.
What does it actually do?
That’s the big question – and scientists don’t have a definitive answer yet.
Researchers found proteins inside the rete ovarii that appear to be secreted by its cells. These could potentially influence the ovary and its function. One region was also connected to nerve fibres, raising the intriguing possibility that the structure could receive information from its surroundings and communicate with the ovary. Think of it like a version of cycle syncing being routed direct to your uterus.
Rather than being biological scaffolding left over from development, the rete ovarii may therefore play some role in maintaining or supporting the ovary.
Does this mean we’ve discovered a new organ?
Not quite. We’ve known the rete ovarii exists, what’s changing is our understanding of what it might be doing.
Researchers suggest it could potentially be considered another component of the female reproductive system, sitting alongside better-known structures such as the fallopian tubes. But there’s still a lot scientists don’t know.
Future research will investigate how the rete ovarii responds to hormones, diet, immune activity and other signals in the body. But its rediscovery is a fascinating reminder that even in human anatomy, there are still surprisingly fundamental questions left to answer.
For more on the changing landscape of reproductive health, read about the breakthrough test that could detect endometriosis via menstrual blood and why PCOS has finally been renamed.
