Aside from the hilarous responses on yah.oo answers to "how long does sperm last within the human body?" (my favorites were "too long!" and "two days if you are trying to get pregnant, five days if you don't want to get pregnant"), I found this delightful article about Sperm Transport in the Female Reproductive Tract. I love that! All those little sperm thinking, what kind of transport should I use? Should I catch the bus? Or ride my teensy sperm-sized motorbike?
And a bonus - the article features a picture of sperm nestling into a "ciliated area of Fallopian tube epithelium" - please tell me this doesn't remind you of Nemo hanging out among the fronds of the sea anenome? (the white arrows point to the heads of the sperm)
Image from here.
I was reading out bits of this article to El Prima, and told her sperm had a usual swimming speed of 5mm per minute, and she said, that's faster than Ian Thorpe. Indeed it is. Given that sperm are only 5 microns in size (admitedly not including their tails), it would be like Ian Thorpe swimming at 1200 km per hour!
The upshot is, who knows. Who knows whether they got there in time, who knows whether they survived long enough. I got sad news yesterday that my friend doing IVF had a negative blood test - and am hoping the little fertility charm works for her next time. We're still waiting for our lottery ticket to be called, but in the meantime, I'm distracting myself with all these scientificky words:
In the uterus, muscular contractions may enhance passage of sperm through the uterine cavity. A few thousand sperm swim through the uterotubal junctions to reach the Fallopian tubes (uterine tubes, oviducts) where sperm are stored in a reservoir, or at least maintained in a fertile state, by interacting with endosalpingeal (oviductal) epithelium. As the time of ovulation approaches, sperm become capacitated and hyperactivated, which enables them to proceed towards the tubal ampulla. Sperm may be guided to the oocyte by a combination of thermotaxis and chemotaxis. Motility hyperactivation assists sperm in penetrating mucus in the tubes and the cumulus oophorus and zona pellucida of the oocyte, so that they may finally fuse with the oocyte plasma membrane.
So now I've got scientific evidence that fertilization can occur when the sperm arrive "up to five days before ovulation". Which leaves me singing my strangely hopeful little song, "Who knows, who knows who knows who knows".