Don’t Call It a Comeback

For over a century, a part of the female reproductive system was dismissed as unimportant.

However, a new study suggests that this “mysterious orphan structure” could actually play a critical role in fertility and the health of the ovaries.

First identified in 1870, the rete ovarii is a small structure located in the ovary that has historically been largely ignored. Early editions of Gray’s Anatomy featured illustrations of it, but gradually, it faded from textbooks and was considered a non-functional element of the adult ovary.

A turning point came in 2024 when researchers published a paper titled “Rediscovering the rete ovarii, a secreting auxiliary structure to the ovary.” This study explored the development and function of the rete ovarii in mice.

The structure, shaped like an extended horseshoe at the base of the ovary, consists of three types: the intraovarian rete (IOR), the extraovarian rete (EOR), and the connecting rete (CR), which are present from birth into adulthood.

When researchers injected fluid into the EOR, they observed that it moved towards the ovary, hinting that this structure might be involved in ovarian function.

Moreover, the EOR appears to have links to both the nervous and circulatory systems. Its cells are closely connected to blood vessels supplying the ovaries and also receive inputs from nearby nerves. These cells are often found close to macrophages, which are immune cells that help safeguard the body.

The research team also found receptors for hormones like estrogen and progesterone, which are significant for reproduction and women’s health in general.

Some proteins released by the rete ovarii are thought to be involved in the maturation of eggs and the wellbeing of ovarian follicles. Their activity seems to increase with rising estrogen levels, indicating a response to hormonal fluctuations throughout the reproductive cycle.

These discoveries could shed light on how the rete ovarii affects fertility and ovarian health. Dilara Anbarci, a co-author and developmental biologist at the University of Michigan, expressed optimism about driving further exploration into female anatomy: “There’s still so much we can’t even begin to comprehend about female anatomy.”

Despite over a century of interest, researchers have never reached a consensus on the function of the rete ovarii.

The renewed focus on this structure has sparked conversations on social media, where many women are condemning the traditionally male-dominated medical research field for neglecting and effectively erasing this component of female anatomy.

Comedian Michelle Wolf voiced her frustration about the situation in a TikTok video that quickly gained popularity, stating, “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 also remarked on the rete testis, which is considered the male counterpart of the rete ovarii—the authors of the 2024 study deemed the rete ovarii “more complex”—and noted its continued presence in anatomy textbooks.

“Being overlooked by a man because they didn’t think you were important, rete ovarii, we’ve all been there. Welcome back, baby.”