The rete ovarii, a small structure beside the ovary first described in 1870, has been rediscovered in a 2025 eLife study in mice. Researchers mapped three regions that persist into adulthood and form tubular channels that may shuttle protein-rich fluid and release factors tied to egg maturation; activity rises with estrogen. The study raises questions about the rete's role in human fertility, emphasizing the need for further research into female reproductive biology.
Rediscovered Rete Ovarii: The Small Ovarian Structure Making a Big Comeback
What Is the Rete Ovarii? The 'Forgotten' Part of the Ovary Is Finally Getting Its Due
Raise your hand if your OB-GYN has ever mentioned the rete ovarii. (I'll wait.)
If that name is unfamiliar, you're not alone. The rete ovarii is a tiny anatomical structure that sits against the ovary and was first described in 1870. It even appeared in early editions of Gray's Anatomy, but for decades scientists could not identify a clear function. Labeled a "functionless vestige," it was often dropped from textbooks — until now.
How It Was Rediscovered
The renewed interest began when developmental biologist Jennifer McKey, imaging mouse ovaries at Duke University, noticed a horseshoe-shaped formation she didn't recognize. After consulting older literature, she realized it was the long-overlooked rete ovarii.
What the 2025 Study Found
A 2025 study published in eLife mapped three distinct regions of the structure — the intraovarian rete, the connecting rete, and the extraovarian rete — and showed that all three persist into adulthood in mice. Far from being idle, parts of the rete form tubular channels that appear to move protein-rich fluid toward the ovary. The structure is also surrounded by blood vessels, nerve fibers, and immune cells.
Researchers found that some proteins released by the rete ovarii are associated with egg maturation and follicle health, and that their activity increases when estrogen levels rise. One scientist described the rete as an "ovarian antenna," suggesting it may sense and transmit cues important to ovarian function.
Important Caveats: Mice vs. Humans
Crucially, the eLife study was conducted in mice. Humans do have a rete ovarii, but whether it functions the same way in people has not been established. "We do not yet know whether the same functional mechanisms operate in humans or whether the rete ovarii has a clinically significant role in human fertility," says Dr. Snehal Kohale, OB-GYN, fertility specialist, and founder of Ova Care.
"A structure being poorly understood does not necessarily mean that it is biologically irrelevant," Kohale adds, noting that the rete ovarii's past omission from curricula illustrates how scientific understanding evolves with new evidence and changing research priorities.
Why This Matters
The finding highlights persistent gaps in female reproductive biology and underscores the need for more targeted research. Conditions such as endometriosis, polyendocrine metabolic ovarian syndrome (PMOS, formerly PCOS), and infertility still lack full mechanistic explanations, and structures like the rete ovarii may hold clues.
For now, your clinician probably won't bring up the rete ovarii at your next checkup. But as researchers probe its role — and whether mouse findings translate to humans — the rete ovarii may move from obscure anatomical footnote to an important piece of ovarian biology. Hopefully, future generations of clinicians will know its name and significance.
Note: This article summarizes findings from animal research. Human relevance remains to be confirmed through further study.
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