The Vagina Museum has highlighted a sketch of the human vulva by Leonardo da Vinci, which appears to be missing a few major key details. 

Da Vinci, as well as excelling in painting and inventions that wouldn't be able to work for hundreds of years, was a keen anatomist, performing many dissections during his time and making detailed sketches of what he saw. 

Though he kept his studies of anatomy private and didn't consider himself to be an anatomist by profession, he did occasionally publish his work. This includes the famous Vitruvian Man, showing the "ideal" proportions of the human body.

However, he clearly needed to spend a little more time on the vagina, if this rough sketch is anything to go by.

Like so many men before and afterward, da Vinci appears to not have noticed the clitoris – or the labia minora. This, however, was probably due to the focus of the piece: the anus. 

"The focus of the page is not the anatomy of the vulva – he's more interested in the anus and trying to work out how the sphincter muscles work," the Vagina Museum wrote. "The pretty, swirly designs are his theories as to how the muscles are laid out."

He may have decided to save himself a little drawing time by not drawing the labia minora and clitoris, instead sketching how he thought the anus worked. Unfortunately, his theories on the anus were incorrect too.

Da Vinci correctly guessed that muscles are able only to pull, not push, but didn't quite get how the sphincter worked. Rather than a ring-shaped muscle that tightens to close and relaxes to open, he thought there were five muscles involved in one of the worst tasks of the human body (we're talking about the anal sphincter here).

For this, he had no explanation.

"Why the muscles of the anus are odd in number; and if this disparity were necessary, why were three or seven not chosen rather than five?" he wrote, unable to pose a reason. 

However, don't take the lack of detail in the image to mean that he was having a lazy day. In fact, he may have caught evidence of a prolapse.

"The urethral orifice is almost papilliform, and as this individual had given birth multiple times there may have been some prolapse," the Royal Collection Trust wrote of the image. "A weakness in the musculo-tendinous floor of the pelvis which holds the bladder."