For more than a century, a mysterious structure attached to the ovaries was dismissed as functionless. Now, scientists are discovering that it might play a much bigger role in reproductive health than anyone had realised.
When we think about female reproductive anatomy, we tend to think of the same familiar structures: the ovaries, fallopian tubes, uterus and cervix. They are the subjects of biology lessons, health appointments and countless conversations about periods, hormones, and fertility.
But what if there were another piece of the puzzle that we had largely forgotten about?
Meet the rete ovarii: a small, intricate network of tissue associated with the ovaries that scientists have known about since the nineteenth century, yet which has largely disappeared from modern anatomical textbooks. Long dismissed as a functionless remnant of embryonic development, the rete ovarii is finally receiving renewed scientific attention. And the findings could change how we understand the female reproductive system.
So, what exactly is the rete ovarii?
First described in 1870, the rete ovarii is a network of epithelial tissue connected to the ovary. It consists of three interconnected regions: one within the ovary, one extending beyond it, and a connecting section linking the two.
Despite its longstanding presence in scientific literature, researchers never established a definitive function for the structure. Over time, it came to be regarded as a vestigial remnant, something left behind during development that no longer served a meaningful purpose.
Eventually, it largely disappeared from modern discussions of female reproductive anatomy.
However, being poorly understood is not the same as being useless. And in 2022, developmental biologist Jennifer McKey and colleagues brought renewed attention to the structure while investigating how ovaries develop in mice. Their imaging revealed a complex network of tissue that warranted a closer look.
The question was no longer simply what the rete ovarii looked like, but what it was actually doing.
Scientists are discovering that it may be doing quite a lot
In March 2025, researchers published a study in eLife titled Rediscovering the rete ovarii, a secreting auxiliary structure to the ovary. The team, led by Dilara Anbarci and including researchers at Duke University, investigated the structure using advanced imaging techniques and molecular analysis.
Their findings challenged the assumption that the rete ovarii was biologically inactive.
Working with mice, the researchers found evidence that the structure produces secreted proteins and transports fluid towards the ovary. Experiments tracking fluid movement suggested that material travels through its tubular network and into the ovarian environment.
The team also discovered that the rete ovarii is closely associated with blood vessels, immune cells, and nerve projections. These connections suggest that it may interact with its surrounding environment rather than simply existing as an inactive remnant.
In other words, the rete ovarii appears to be much more complex than its reputation suggests.
Researchers have proposed that it could help regulate the ovarian environment, potentially contributing to ovarian development and maintenance. Its secretions may contain proteins involved in reproductive processes, although the precise effects of these substances remain under investigation.
It is an exciting development, but an important distinction remains: these findings were demonstrated in mice. Exactly how the rete ovarii functions in humans, and whether it has a measurable effect on fertility, still needs to be established.
Why did it take so long for scientists to look again?
Perhaps the most striking part of this discovery is that the rete ovarii was not hidden or unknown. Scientists had described it more than 150 years ago.
Instead, it was largely overlooked because researchers had come to believe it had no meaningful function. Once a structure was classified as a developmental remnant, there was less incentive to investigate what it might be doing in adulthood.
The renewed interest in the rete ovarii illustrates how scientific assumptions can shape the questions researchers ask, and which questions they stop asking.
It also highlights the importance of studying biological structures in their entirety. Earlier investigations often relied on thin tissue sections, making it difficult to understand how the rete ovarii’s different regions connected. More sophisticated three-dimensional imaging has allowed researchers to examine its architecture within the surrounding ovarian tissue.
The result is a reminder that scientific progress does not always mean discovering something entirely new. Sometimes, it means looking at something familiar with better tools and a more open mind.
What could this mean for women’s reproductive health?
The rete ovarii’s potential role in ovarian function raises several questions that researchers will now need to investigate.
Could it help regulate the environment in which ovarian follicles develop? Does it respond to hormonal fluctuations? Might it contribute to maintaining ovarian tissue throughout a person’s reproductive life?
These are possibilities rather than established conclusions. Nevertheless, understanding the rete ovarii could eventually help scientists develop a more complete picture of how the ovaries function.
Some researchers have also raised the possibility that it could influence fertility or the reproductive lifespan. If future studies establish a meaningful role in these processes, the implications could be significant. For now, however, there is not enough evidence to suggest that the rete ovarii directly controls ovulation, determines the timing of menopause, or offers a new treatment for infertility.
That uncertainty is precisely why further research matters.
How much of the female body are we still learning about?
The story of the rete ovarii is about more than one overlooked structure. It raises a broader question about how we study female anatomy and how quickly assumptions can become accepted knowledge.
Women’s reproductive health has many unanswered questions, from the mechanisms underlying endometriosis to the causes of ovarian ageing. Discoveries such as this demonstrate the value of investigating the structures and processes that have received comparatively little attention.
It would be premature to suggest that the rete ovarii will revolutionise reproductive medicine. The research is still developing, and findings in mice cannot automatically be applied to humans.
But that does not make the discovery any less interesting.
A structure once dismissed as functionless may turn out to have a meaningful role in ovarian biology. Scientists are now investigating that possibility instead of accepting an old assumption as the final word.
As developmental biologist Dilara Anbarci points out, our understanding of female anatomy remains far from complete. She hopes that the renewed interest in the rete ovarii will encourage scientists to revisit long-held assumptions about the ovary and investigate the questions that have gone unanswered for far too long.