The Rete Ovarii is a network of tissue directly associated with the ovary. Scientists have known about it for more than a century, but it was largely considered a functionless remnant of development and received relatively little research attention. New research suggests that assumption may have been very wrong.
Could that eventually change what we know about conditions like PCOS/PMOS, infertility, menopause or other areas of reproductive health? Perhaps. Right now, we simply don't know. But the fact that scientists are looking again—and people are paying attention—is exciting.
There is also reason to be frustrated by how we got here.
That's a pretty remarkable gap. But it's also an opportunity for course correction. The rete ovarii may turn out to be an important missing piece in our understanding of ovarian biology. It may not. That's the thing about research: sometimes an overlooked structure changes how we understand the body, and sometimes its role turns out to be much narrower than we imagined.
We don't have the answers yet. But we're finally asking the questions.
What is the rete ovarii?
The rete ovarii (RO) is a network of tissue closely associated with the ovary. It develops alongside the reproductive system and has been identified across many mammalian species, including humans. It isn't new.
The structure was first described in the nineteenth century and appeared in early anatomical literature. What scientists haven't understood very well is what it actually does. For much of modern medical history, the rete ovarii was described as a vestigial structure: essentially, tissue left behind during embryonic development that appeared to have little or no function in adulthood.
The structure was first described in the nineteenth century and wasn't exactly hidden. It even appeared in drawings of the ovary in early editions of Gray's Anatomy.
And then, remarkably, it largely disappeared from modern anatomical teaching.
The researchers behind the 2025 eLife study note that while the rete ovarii appeared in early Gray's Anatomy illustrations, it was omitted from more recent textbook representations of the female reproductive tract. As the structure came to be regarded as a functionless vestige, it also received relatively little research attention.
There were scientific reasons for that assumption. Earlier observations suggested portions of the rete contracted or degenerated after birth, and researchers hadn't established a clear function for it.
But there's an important difference between:
"We have demonstrated that this structure has no function."
and
"We haven't figured out what this structure does."
The rete ovarii landed much closer to the second category.
We've been wrong about "useless" anatomy before
This isn't entirely unusual in medicine. The appendix was famously labelled vestigial for generations. We now know it contains substantial immune tissue and appears to play roles in immune function and the gut microbiome.
Then there are the tonsils. People can live without them, but that doesn't make them useless. They're lymphatic tissue involved in immune defence. Biology is full of structures that aren't essential for survival but still perform a function.
And this isn't the first time female anatomy has played catch-up
Consider the clitoris. It obviously wasn't unknown to medicine, but detailed understanding and representation of its complete anatomy lagged badly.
As recently as 2005, Australian urologist Helen O'Connell and colleagues published a comprehensive anatomical account using research that included dissection, microdissection, MRI and three-dimensional reconstruction. Think about that. Researchers were still clarifying and documenting the complete anatomy of an organ whose primary known function is sexual sensation in the twenty-first century.
The rete ovarii is another reminder that "human anatomy" has not always meant that every human body received the same degree of scientific attention. Research doesn't simply happen because a structure exists. Someone has to think the question is worth asking, fund it, investigate it, and decide that information matters enough to teach.
What did scientists discover about the rete ovarii?
In 2025, researchers published a study in eLife that used advanced imaging, molecular markers and proteomic analysis to characterize the rete ovarii in mice in unprecedented detail. Researchers identified three distinct regions:
-
Intraovarian rete: located within the ovary.
-
Connecting rete: connecting the internal and external portions.
-
Extraovarian rete: a tubular structure outside the ovary.
The researchers demonstrated that material inside the extraovarian rete moved toward the ovary, and the structure was closely associated with blood vessels, immune cells, and neuronal projections. Put that together and "useless leftover" starts looking like a pretty inadequate description.
The researchers propose that the rete ovarii may function as an auxiliary structure to the ovary, potentially contributing to ovarian development and homeostasis. That is a significant finding.
Could the rete ovarii change what we know about reproductive health?
This is where things get really interesting. If the rete ovarii is an active structure that interacts with the ovary, could it be relevant to conditions like PCOS/PMOS, PMDD, endometriosis, infertility, menopause, or ovarian cancer? Perhaps. And that perhaps is exciting.
If we've been working with an incomplete understanding of ovarian anatomy and function, it's reasonable to ask whether studying the rete ovarii could eventually add another piece to the puzzle of conditions we still don't fully understand. Maybe it will. Maybe it won't.
We simply don't have enough evidence yet to know. The 2025 research was primarily conducted in mice. It provides compelling evidence that the rete ovarii is biologically active, but it does not establish a connection between the rete ovarii and any of these conditions in humans.
Why the attention around the rete ovarii matters
There's another hopeful part of this story: people are talking about it. The rete ovarii has travelled beyond academic journals, spreading across social media and bringing a relatively obscure piece of reproductive anatomy into public view. That's a good thing.
Widespread awareness can help create an environment where these questions are harder to ignore. Scientists are looking. People are asking questions. And instead of treating what we don't know as the end of the conversation, we're treating it as a reason to investigate further. That's what course correction looks like.
Why is a period care company talking about the rete ovarii?
Because bodily agency requires information. Access to period products is only one part of agency; access to reliable information matters too. joni's goal with menstrual-health education isn't to tell you what to think about your body. It's to help you understand what we know, what we don't know and what questions are worth asking next.
What does the rete ovarii have to do with your period?
Not because your choice of pad, tampon or period underwear has anything to do with your rete ovarii. The connection is much more fundamental.
Your period is one visible part of an extraordinarily complex reproductive system involving communication between the brain, hormones, ovaries and uterus. As the rete ovarii story rather spectacularly demonstrates, we're still learning how that system works. Period care shouldn't just be about managing blood. For us, it's also about giving people the products, information and language they need to understand and care for their bodies.
Frequently Asked Questions about the Rete Ovarii
What is the rete ovarii?
The rete ovarii (RO) is a network of tissue closely associated with the ovary that develops alongside the reproductive system in many mammalian species, including humans.
Is the rete ovarii a newly discovered organ?
No. The structure was first described in the nineteenth century. What is new is research providing stronger evidence that it may have active, important biological functions.
Why did scientists think the rete ovarii was useless?
Textbooks often described it as a "vestigial" or functionless remnant because earlier observations suggested portions degenerated after birth, and researchers simply hadn't figured out what it actually did.
What is the rete testis?
The rete testis is a related structure in male anatomy that helps transport sperm. Unlike the rete ovarii, its function is an established part of reproductive biology.
Does the rete ovarii cause PCOS or PMOS?
There is currently no evidence establishing a connection between the rete ovarii and PCOS/PMOS in humans.
The takeaway
Yes, this story should make us uncomfortable. A structure associated with the ovary was known for more than a century, poorly understood, given relatively little attention and frequently dismissed as functionless.
Researchers looked again. And it turns out there is considerably more going on.
There are still fundamental aspects of female reproductive biology that we don't fully understand. Be frustrated by that. Be excited that researchers are asking these questions now. And then demand the thing women's health has needed all along: more research, better research, and the willingness to keep asking questions.