Rete Ovarii: The Female Body Part Ignored, Then Rediscovered

Ever heard of the “rete ovarii”?

If you answered “no”, you have every reason. Even though it was discovered and described in humans over 150 years ago (drawings of it appear in early copies of Grey’s Anatomy, an anatomy reference book that’s been running since 1858), scientists quickly dubbed it purposeless.

The structure, which lies near the ovaries, became so ignored that it was eventually removed from textbooks altogether. It was considered a “functionless vestige” of the adult ovary, meaning experts decided it was a useless evolutionary holdover.

But a study from Duke University suggests that the body part might play a role in fertility and ovarian health and maintenance for those with wombs.

While the research was conducted on mice, researchers think the findings could apply to humans too; the structure has been seen in lots of other mammals, and our sex organs develop in a manner very similar to those of a mouse.

Sometimes shortened to RO, the rete ovarii is a horseshoe-shaped “network of tubules and cords” that is attached to the ovary.

As it happens, those with penises have an equivalent: the rete testis, which we know helps to transport sperm.

We don’t know yet – but new imaging technology has offered exciting suggestions which would render the rete ovarii far from useless.

The “rediscovered” rete ovarii was found to have three distinct regions in both living mice and animals’ dissected tissue:

1. The intraovarian rete (IOR), found in the ovary
2. The extraovarian rete (EOR), made up of that network of tubes we mentioned earlier
3. The connecting rete (CR), which joins up the IOR and CR

The EOR seems to contain and produce proteins like insulin-like growth factor-binding protein 2 (IGFBP2), which may play a role in ovary function.

And after placing fluorescent dye in the EOR, they found it seemed to propel liquid towards the ovary, too. That suggests it may have a role in how the appendage operates or maintains itself.

Not only that, but experiments pointed to the possibility that the rete ovarii might switch on genes that affect how hormone receptors work.

The paper reads: “The direct proximity of the RO to the ovary suggests that it is functionally linked to the ovary and may play an important role in ovary development and homeostasis [self-regulation].

“Based on the cell biology, transcriptome and proteome of the RO, I hypothesise that the RO acts as an antenna for the ovary and plays an important role in ovary homeostasis and fertility.”

More research is needed to confirm or disprove that hypothesis, or indeed to find any other possible uses of the rete ovarii.

Speaking to Live Science, the study’s lead author, Dilara Anbarci, said: “There’s still so much we can’t even begin to comprehend about female anatomy.

“I hope this encourages more investigation in reevaluating what we don’t already know about the ovary.”