5. SOME BASIC STUFF ABOUT HOW CONCEPTION HAPPENS

RAH - This is just about impossible to summarize in a few lines. Rather than try to do it here, I would suggest that you read Chapter 4 in _ TCoYF_ by Toni Weschler; if you want more detail, read Toni's Appendix E. The following subsections are mainly different pieces of the conception puzzle, that get asked about most often on the newsgroups. - RAH

20 percent of all infertility problems are connected to both partners. (50% female only, 30% male only)

Does any one know FOR SURE how long sperm can live and also how long the egg can live after being released? I've read here that some people think that the sperm can live only a few hours same as the egg? But they say that that's not a positive..Does any one know the actual amount of time that they live?

The experts (I'm relying on Toni Weschler here) say that the egg lives a maximum of 24 hours after release from the follicle (or 48 hours combined lifespan if two eggs are released in a given ovulation). The *average* egg lifespan, as opposed to maximum possible lifespan, is closer to 12 hours.

Sperm are more variable -- they can live up to 5 days, maybe a little longer, if cervical [fluid] is present in the female tract, and if conditions are otherwise healthy. If there's no cervical [fluid], they can die off within a few hours after ejaculation. (Sensitive little critters, aren't they? :-) )

Also isn't a woman born with all the eggs she'll ever have for her entire life time, as men's sperm are being reproduced throughtout their life time?? I've heard yet again different opinions.....Thanks for any info...

In a word, yes -- all your eggs are born with you; but all his sperm get manufactured on-site. The total time frame to manufacture a new sperm-cell from scratch is 70-80 days.

I'd like to add another sperm question: How long does it take a sperm to swim up to the fallopian tube and to the (ideally) waiting egg? I keep posting this question around and never get an answer (or even a guess!)

I read in the book _A Child Is Born_ that it takes 6 hours to make the journey. Some sperm won't make it through the cervix and some will stay behind at the cervix and wait (if the [cervical fluid] is right), while others will try to get through the uterus and the fallopian tubes. I rented the video of A Child Is Born. Sperm look like a bunch of brainless entities swimming in a race. Some go the wrong way. Some go in mindless circles. Some bump into and try to enter any cluster of cells that look like an egg. Some are double-tailed and can't swim straight, some are weak and mal-formed, many die on the way. A pitiful sight for sore eyes, in my opinion. But, some are strong and resolute and fight their way to the finish line where they get to try to bump into the egg. Only one is allowed to enter her majesty, the egg. I found the video fascinating, and kept seeing parallels to male/female relationships in human society. I've known men who act like some of these sperm, if you know what I mean. (I know I'm weird..) Anyway, I read the book and saw the movie. I recommend it, but viewer discretion should be used if feeling too vulnerable to view the birth process.

I have read that on an average (whatever that is), sperm swim about one inch per hour. In that same book (I don't remember which one) it said that the average distance that sperm have to travel, from cervix to ovum, is about 6-8 inches. So, I always assume about 6-8 hours [for sperm to reach the egg].

If you are talking about "natural" conception (i.e. not IUI), the sperm has to work its way through the cervical [fluid], and much is stored up in the cervical glands (that is how they can stick around for 3 days or more). What I ... remember is that, when the egg is being released, chemicals are produced that inspire the sperm to dash up the fallopian tubes and find the eggs. I've also read that the sperm MUST hang out in the cervical [fluid] for several ... hours before they become "capacitated" and able to make the swim and fertilize the egg. So it takes at least that long, plus another hour or so to swim to the egg.

I'd like to add another sperm question: How long does it take a sperm to swim up to the fallopian tube and to the (ideally) waiting egg? I keep posting this question around and never get an answer (or even a guess!)

Could it be that none of us knows the answer to this question? I would like to know too! I guess I though it was a couple of hours, but given the [Dec 95] NEJM findings, maybe it's longer!

I don't know the answer to this one, but I remember something I read recently. Apparently sperm have a very primitive sense of smell and they have to smell out the egg. So I guess the answer is that it depends on how well they smell! (Or how good that egg smells to them!)

The follicle is a swollen area on the ovary that contains the egg. Under "normal" circumstances, about 15 to 20 follicles start growing at the beginning of each monthly cycle, but typically only one follicle "wins the race" and grows large enough to release its egg (this is assuming no superovulatory drugs such as Pergonal, Metrodin, etc.) The winning follicle grows to the size of a small grape, so it's very visible on ultrasound.

After the egg is released, the empty follicle is just a hollow shell of granulosa cells, which quickly collapses back onto the ovary and is changed into a different structure, the corpus luteum, by the luteinizing hormone. The corpus luteum then starts secreting progesterone, which helps the (hopefully!) fertilized egg to find a nice, safe home in the ripened endometrial lining of the uterus.

Just to add my 2 cents worth. Last nite on CBC's "The Nature of Things" with David Suzuki (an excellent Canadian show) the topic was "Why sex?". It was about the role sex plays in the whole world. Everything from bacteria and viruses to whales do it. Why is some sex asexual and therefore clones they asked?

Well, one theory is that sex creates new variations of us and therefore makes new people less susceptible to disease and infections from our natural predators - bacteria and viruses and protazoas. One theory as to why some sperm linger at the mouth of the vagina is that there are different sperms - some are "killer" sperms just there to destroy any other sperm that may be present. Other sperm are there for the fertilizing of course.

A study done at the U. of Manchester in England, proved that women were 3 times more likely to become pregnant by having sex with another man other than their husband! This was a double blind study and I forget the name of the researcher, but hey, it sounds worthwhile checking out! I'm not going to cheat on my hubby though. It's not worth the heartache.

Another theory is the more likely one male is to having offspring, the smaller the testicles, and vice versa. In bonobos (a type of ape - our closest genetic relatives) there is a high incidence of multiple inseminations by many males with one female, therefore the males have very large testes and many sperm. Gorillas have a "harem" basically and a dominant male so they have very small scrotums and little sperm but it still gets the job done.

Very interesting show. You can probably request your local PBS station to obtain a copy from CBC and show it in your area if your are interested because I've seen the [American] PBS station from Watertown (WNPE/WNPI) show "The Nature of Things" show before. Something to ponder while lying in bed having sex, isn't it! LOLFL!!!!