A female body part never reached books for a century because scientists thought it was useless; now researchers say it is crucial for ovary function

Women have been kept in the dark about more than just their abilities and history, they still don’t know one of the most important things about themselves: their body. For more than a hundred years, an organ in the female reproductive system was written off as useless. However, a recent study has revealed that what researchers called a “mysterious orphan structure”, may play an essential role in fertility and keeping the ovaries healthy.

A rediscovered organ

First discovered in 1870, the rete ovarii is a small structure on the ovary that has historically received little to no attention. While early editions of ‘Gray’s Anatomy’, the classic human anatomy reference book first published in London in 1858, did include drawings of the appendage, eventually, it completely disappeared completely from medical textbooks and came to be regarded as a functionless part of the adult ovary.That assumption is particularly shocking because the RO is found across a wide range of mammals, including guinea pigs, cows, cats, sheep, pigs, dogs, monkeys, camels, and humans. Previous studies had hinted that it could produce and release substances, but this possibility was never experimentally confirmed. Without a clear function, the RO remained something of an anatomical mystery.But in 2024, a research team from Duke University 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.The rete ovarii is an extended horseshoe-shaped “network of tubules and cords” at the bottom of the ovary. It 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 that 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, which are 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.According to co-author Dilara Anbarci, a developmental biologist at the University of Michigan in Ann Arbour, the findings could offer clues about how the structure contributes to fertility and ovarian health. “There’s still so much we can’t even begin to comprehend about female anatomy,” said Anbarci to ScienceNews. “I hope this encourages more investigation in reevaluating what we don’t already know about the ovary.”

Social media backlash

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 rediscovery of the organ is also making waves on social media, where women are criticising 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 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.”