Sperm are the swimming, fighting parts of the complicated reproduction process that gives birth to more and more of us each day. So how does this process occur? It all starts with the building blocks of life and the composition of spermatozoa.
The sperm has a few different components, with all the "good stuff" being stored in the head. The file with this information (DNA) is called the nucleus and it will eventually be the only thing to merge with the female’s egg. The blueprints for life exist in this most tiny of spaces; the coding that will eventually determine so much of the physical life that we enjoy.
The only way for this life coding to get where it needs to go, is by "swimming." This action actually refers to their motility, which means that they can move on their own. To create motion the spermatozoa have a tail that is lined with mitochondria, which drive the swimming motion of the sperm. Mitochondria are sub-cellular, meaning that they are smaller than the cells that they inhabit, and their function is to take various types of nutrients found in the body and convert it into energy, thus allowing them to perform all sorts of useful tasks - like reducing the effects of your hang over.
Having an understanding of the basic make-up of the sperm’s physical structure, we can now examine how sperm are created, spend their lives and are involved in the birth of new life.
Sperm Production or Spermatogenesis
Thirteen years for men (and a little younger for women) marks the beginning of puberty and the initiation of sperm production in the male. It can take between 64 to 72 days for the generation of a new sperm cell.
Men must be constantly making new sperm, in rapid overlapping production schedules, because during every ejaculation he expels roughly a quarter of a billion spermatozoa. This is a very rigorous schedule for the body to maintain, so keeping the system healthy is of utmost importance. For information on how to keep all the pistons firing properly, please refer below to Sperm Count.
The sperm begin their lives in two glands located in the scrotal sac, directly beneath the penis. Initially spermatozoa cross the rete testis and the efferent ducts to rapidly pass into the epididymis where they are stored. Sperm resides in the caput (or head), then the corpus (or body) and finally in the cauda (or tail) of the epididymis. As sperm navigate to the epididymis they change significantly to become motile, change shape and undergo physical alterations. Once located in the epididymis they stay and grow into maturity until they are ready for discharge then are mixed with semen and "released".
During the growth phase of these future fertilizing “warriors”, a gland known as the anterior pituitary produces hormones that put hair on men’s chest (FSH) and the manly voice in their throat (LH), as well as all those other characteristics that make men more distinguishable from women.
Once the spermatozoa are ready to get out into the world, they move along to the vans deferens and then hook up with the urethra. Along the route to the seminal fluid (that serves as a vehicle for the sperm) it gets some key ingredients added to it. The seminal vesicles add fructose (sugar) and prostaglandins to the sperm; together they promote and regulate the sperm’s health while in transition. The prostate secretes a non-acidic fluid that gives semen its color, and the Cowper’s Gland produces a mucus-like fluid that acts as a lubricant.
The male body also has a system of neutralizing the acidity of any potential urine that may remain in the urethra. All these different fluids and sperm make up what is known as semen, which is ejaculated out of the body through a series of soft muscular movements that are initiated during arousal and subsequent stimulation. As the body approaches a state of orgasm, marking the release of sperm in semen, the muscles that control the prostate, urethra and testicles all contract. They lift the scrotum and all the muscles force the sperm out through the urethra at almost 45 km/h. This whole process takes about 3 to 10 seconds, though this amount of time tends to decrease over a man’s lifetime.
Theories also suggest that the contractions associated with female orgasms pull sperm from the vagina to the cervix, where it's in a better position to reach the egg. Sperm, in the vagina, can only survive about six hours due to the acidic vaginal secretions. The cervical mucus present when ovulation is near, is more alkaline and more hospitable to sperm. The egg white consistency of the cervical mucus helps the sperm move more easily through the vagina to the cervix, increasing the chance that the sperm will be in the correct location for fertilization to occur...
The Final Leg
So how do sperm manage to negotiate their way from the vagina through the deep caverns of a woman’s cervix, tubes and ovum?
The fact is, that like a "moth to a flame" or a "fish to a lure", the female body produces a "scent" that is either produced by the egg itself or perhaps more generally the woman’s reproductive tract. This process is known as "chemoattraction," and makes the sperm swim aggressively; charging towards their destiny, and the lottery of procreation.
Upon their arrival at the egg, the sperm completely envelope it's outer shell (known as the extra cellular coat).
After docking, the egg undergoes some fundamental changes that allow one sperm to break through the protective coat of the egg and merge, fusing into one.
Sometimes sperm that have undergone this chemical change can exhibit increased motility or hyperactivity, and with a little extra shake in their step continue on toward the nucleus.
The sperm now moves through the outer membrane.
From this point on the two nuclei merge, potentially creating of a new, and thoroughly unique organism.