Women’s small intestines are longer than men’s, with this extra length probably helping them better absorb fat and other nutrients when needed for pregnancy and lactation.
“The small intestine is all about absorption, absorption, absorption,” says Amanda Hale at North Carolina State University. “This is where you get most of your nutrients from everything you eat.”
In anatomy classes, says Hale, students are often not taught about individual differences and instead focus on organs that follow textbook descriptions. But these differences can help inform health decisions, she says.
“There’s a kind of formulaic approach focused on what’s average or what most people experience,” Hale says. “It’s versus individualized medicine, where you look at whether there are specific characteristics about a person’s digestive system that might be contributing to what’s happening and not meeting the status quo.”
concerned that important differences are not being detected, hale, Erin McKenney — also at North Carolina State University — and his colleagues measured the digestive organs of 21 female and 24 male human adult cadavers that were donated to Duke University, North Carolina.
They found that, on average, the small intestines of male cadavers were a little over 4 meters in length, while those of female cadavers were 30 centimeters long. A statistical analysis suggests that this difference was not a finding of chance.
“If [women’s small intestines] are longer and have more surface area, which means they can pull more of what they eat,” Hale says. “It may be related to reproduction, and it most likely is.”
However, this physiological difference probably does not fully explain why some gastrointestinal conditions are more common in one sex than the other. For example, Temple Health in Pennsylvania reports Women are more likely to develop Crohn’s disease — inflammation of any part of the digestive tract, from the mouth to the anus — but men are more likely to develop ulcerative colitis — inflammation of the large intestine, from the colon to the anus.
Sex-related differences in our immune systems and genetics probably play an important role in these conditions, says McKechnie.
The researchers also found that the length of other limbs differed between carcasses, but there was less of a clear indication of variation between the two sexes. For example, the gall bladders of the carcasses ranged from 5.5 to 12.5 cm in length, while their appendages ranged from 1.4 to 12.7 cm.
Some carcasses also had colons—the longest part of the large intestine that removes water and some nutrients from partially digested food—that were more than twice as long as others.
In general, limb length did not correlate with the height of the carcasses, which ranged from 149 to 184 cm, nor did the size of their other limbs. For example, having a long gallbladder is not necessarily related to a long appendix.
Overall, the study points to the importance of taking people’s unique anatomy into account for their diagnosis and treatment, the researchers write in their paper.
“It helps to create an awareness and appreciation for the vast amount of diversity, and how all these different clinical conditions will manifest in different ways,” says McKechnie.
The study was made up of a relatively small number of subjects, but the researchers say this may have strengthened their findings. “It is worth noting here that we found such variation despite only measuring 45 human cadavers,” they write.