OK, for people who want to know this! (Spermatozoon/spermatozoan is a single sperm, spermatozoa is for more than one sperm, that’s why the singular and plural for “sperm” is the same, it’s an abbreviation.)

The making of the sperm takes a full three months – although this is a continual process, not a batch process as some would have you believe (my DH is such a wuss!). Sperm start out as germ cells in the testes, these cells are diploid, meaning that they have two copies of each chromosome, like normal cells. There are layers to these germ cells and they divide all the time, creating copies of themselves (mitosis), replenishing the top layer (sort of like skin – a continual layer at the bottom replenishing the stuff at the top). When the cells reach the top layer, they undergo meiosis, a way to split a cell into four new cells, each containing half of the genetic material.

These cells are still not sperm as we know them. They hang around in the seminiferous tubules just after they have been made, waiting to pass into the epididimus. Rather cleverly, these cells are now classed as “foreign” to the male body, so sperm can’t go on a rampage inside a chap.

Into the epididimus; this is basically where the sperm get their little fast cars. Before, they couldn’t move around, now, they get loaded up with the tail, the mitochondria (the little engines) and the enzymes (destructo-rams) to beat their way into the egg. The nucleus, containing all the genes, hasn’t changed much, but it can now move, power itself and get into an egg. This is where they start to die too – whilst abstaining from sex, the sperm in the epididimus can be re-absorbed into the body and removed in the urine – so very good the sperm are “foreign bodies” to the male now!

Once the sperm leaves the male and enters the female (I’m sure we all know how that happens!) the sperm get to work. Usually, about 60% head straight back out again, leading to the “wet patch” (men never ask for directions…) but of the remaining 40%, they head upwards. There’s a choice of left or right, and so only 20% of the sperm released make it to the ripening ovary/released ovum. However, all this running around takes energy, and the more energy used, the more decrepit the sperm. Even sitting around in the epididimus takes energy, once the mitochondria are added they don’t stop working! Or devouring the sperm’s resources. Y sperm have more mitochondria, so they’re faster and get to the egg first (if they don’t go the wrong way), but die faster. X sperm are slower, but survive longer. In EWCM, the sperm don’t have to work so hard to swim around so last longer than without, when they’re pretty worn out by the time they make it to the ovary and only last a day or so longer. In EWCM, sperm can live for up to 5 days, but that is in absolutely optimal conditions!

Once the egg is released, the sperm “charge” it. They release the enzymes at the front of the sperm to batter the egg and bash their way in. Once a sperm has entered, it sets off a chemical chain reaction to make the egg impenetrable by other sperm – the biochemical equivalent of marking territory. This is very, very quick – almost instantaneous – but it is not unheard of that a second sperm can penetrate the egg. This is, however, very rare.

Well done! Fertilisation has occurred! HTH and if I made any huge errors or left anything major out please let me know, but that's a sperm's life, as I understand it.