From Cory Silverberg,
Your Guide to Sexuality.
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The anatomy of sexual intercourse, or what body parts we use for sexual intercourse and what happens to them when we use them, has been a fascination of artists and scientists for centuries. But our curiosity with what precisely happens “down there” has long been stymied by the difficulty in visualizing and measuring sexual intercourse. After all, how does one “get inside” sexual intercourse? And if you could, what exactly do you measure? Despite the obstacles, artists and researchers have tried to guess at what the anatomy of sexual intercourse may be. And modern technology is now giving us the clearest picture yet of how we come together (even when we don’t).

Leonardo da Vinci’s “The Copulation”

In 1493 Leonardo da Vinci illustrated the anatomy of sexual intercourse with explicit detail based, among other things, on his dissection of bodies. The image included a tract that ran from the brain to the penis (via the spinal cord) which carried semen, and for women a tube from the breasts to the vagina. Da Vinci also conceived of the penis during intercourse as being straight (all notions which have later been disproved).

Publication of Human Sex Anatomy

Originally published in 1933 and then updated and renamed An Atlas of Human Sex Anatomy in 1949, this text offered detailed illustrations of male and female sexual anatomy and the author’s hypothesis of the anatomy of intercourse. Dickinson used glass tubes the size of a penis to simulate vaginal intercourse, and developed a model of intercourse anatomy which suggested that during penetration the penis takes an “s” shape in the vagina.

Masters and Johnson Laboratory Sex Research

To study both the anatomy of intercourse and its physiology, pioneering sex researchers William Masters and Virginia Johnson conducted numerous laboratory studies in the 1960s where subjects engaged in sexual behaviors, including intercourse while being observed and monitored. One of their innovations was to simulate intercourse by having women use a clear plastic dildo to mimic intercourse that could also record changes in the vagina. They observed what they called “vaginal tenting” (upwards and backwards movements of the front wall of the vagina) as well as a significant increase in the size of the uterus during and following orgasm. This research led them to develop their model of human sexual response for men and women.

Using Ultrasound Technology to Map the Anatomy of Intercourse

In 1992 researchers who were investigating a new barrier contraception method used ultrasound to observe intercourse. These initial images (which are not available) are said to be very crude, but interestingly they observed different changes in the vagina and cervix during intercourse depending on the sexual position.

Magnetic Resonance Imaging of the Anatomy of Intercourse

In 1999 four Dutch researchers published the first study where they had people engage in intercourse inside an MRI machine. The still images from the MRI are fascinating and the research broke new ground in “getting inside” the anatomy of intercourse. Apparently it is not an easy task, having sex in an MRI tube, there is a great first person account from one of the female research subjects. This initial research illustrated that during intercourse the penis takes on a boomerang shape, and is neither straight nor “s” shaped as previously hypothesized. It also indicated that the penis appears considerably longer as the “root” of the penis, which does not extend out of the body, is involved in penetration. The research also conflicted with Masters and Johnson’s findings regarding the uterus, in that they observed no increase in the size of the uterus.

Real Time 3D Ultrasound Imaging

In 2005, noting the difficulties in using MRI technology to collect two dimensional data (primarily the requirements that subjects have to stay still and move in a confined space) researchers in England developed an “artificial vagina” connected to a three dimensional ultrasound device which allowed them to study the penis in action (as it were) in real time, and visualize the internal structures and blood flow. This research is preliminary, and they’ve only got so far as proving it can be done, but it does seem like it might be better for studying the anatomy of intercourse from the penis perspective.

Sources:

1. Deng, J., Hall-Cragg, M.A., Pellerin, D. et. al. “Real-time Three-dimensional Ultrasound Visualization of Erection and Artificial Coitus” International Journal of Andrology Volume 29, Issue 2. (2005): 1365-2605.
2. Faix, A., Lapray, J.F., Callede, O., et. al. “Magnetic Resonance Imaging (MRI) of Sexual Intercourse: Second Experience in Missionary Position and Initial Experience in Posterior Position.” Journal of Sex & Marital Therapy Volume 28, Supp. (2002):63–76.
3. Masters, W.H. & Johnson, V.E. Human Sexual Response. New York: Bantam Books, 1980.
4. Schultz W. G. M., Van Andel, P., Sabelis, I., & Mooyart, E. “Magnetic Resonance Imaging of Male and Female Genitals During Coitus and Female Sexual Arousal.” British Medical Journal Volume 319 (1999): 1596–1600.