Don’t call it a comeback.
For more than a century, an organ in the female reproductive system was written off as useless.
However, a recent study indicates that what researchers have called a “mysterious orphan structure” may play an essential role in fertility and keeping the ovaries healthy.
First discovered in 1870, the rete ovarii is a small structure on the ovary that was historically received little attention.
Early editions of Gray’s Anatomy — the classic human anatomy reference book first published in London in 1858 — included drawings of the appendage. But it eventually disappeared from medical textbooks and came to be regarded as a functionless part of the adult ovary.
Then in 2024, a research team published “Rediscovering the rete ovarii, a secreting auxiliary structure to the ovary,” a scientific paper describing their examination of the development and function of the rete ovarii in mice.
An extended horseshoe-shaped tissue at the bottom of the ovary, the organ consists of three distinct regions that persist from birth through adulthood: the intraovarian rete (IOR), the extraovarian rete (EOR) and the connecting rete (CR).
Researchers injected fluid into the EOR and found that it flowed toward the ovary, suggesting the structure may play a role in ovarian function.
They also found evidence that the EOR may communicate with the nervous and circulatory systems: Its cells are closely associated with blood vessels that supply the ovaries and receive direct connections from nerves. The cells are also found near macrophages, immune cells that help protect the body.
The researchers also found receptors for hormones including estrogen and progesterone, which play important roles in reproduction and other aspects of women’s health.
Some of the proteins released by the rete ovarii are involved in egg maturation and maintaining ovarian follicles. Their activity increased as estrogen levels rose, suggesting the structure may respond to hormonal changes during the reproductive cycle.
The findings could offer clues about how the structure contributes to fertility and ovarian health, co-author Dilara Anbarci, a developmental biologist at the University of Michigan in Ann Arbor, told ScienceNews.
“There’s still so much we can’t even begin to comprehend about female anatomy,” said Anbarci. “I hope this encourages more investigation in reevaluating what we don’t already know about the ovary.”
Researchers have studied the rete ovarii since it was first described more than 100 years ago, but they never agreed about its function, according to the authors.
The rete ovarii rediscovery is also making waves on social media, where women are criticizing the medical research establishment — historically male-dominated in both its workforce and leadership — for rejecting and “erasing” a structure in the female body.
Comedian Michelle Wolf called called the news “infuriating” in a TikTok that has garnered more than 130,000 likes.
“The fun thing is that obviously our bodies didn’t erase it because if our bodies just erase things men wanted them to, we wouldn’t have brains,” she said.
Wolf also pointed out that the rete testis, considered the male equivalent of rete ovarii — though the 2024 study’s authors deemed the rete ovarii “more complex” — has remained in anatomy textbooks.
“We research women’s health just about as thoroughly as a man looks for ketchup in the fridge,” she quipped.
“Being overlooked by a man because they didn’t think you were important, rete ovarii, we’ve all been there. Welcome back, baby.”
