Page Links:
A. The male Genital system (together with the Urinary system):
As you see from this diagram, there are several structures involved in the functioning of the male genital system.
2. These are:
- two Testis (= testicles)
- two Epididymis
- two Vas deferens
- two Seminal Vesicles
- two Bulbourethral glands
- one Prostate
- one Urethra
- one Penis
3.
This (genital) organ system is, interestingly, intertwined with another organ system: the urinary system. This connection occurs when the vas deferens connects to the urethra. The urethra (link) is also the pathway for our urine to leave the bladder.
The sperm cells are developed in the testicles and stored in the epididymis. Only when the male ejaculates, are the sperm cells pushed into the vas deferens and transported to the penis.
Although at each ejaculation at least 1 million sperm cells are delivered, the amount, called the semen, is very small; approx. 1-2 millilitres. The secretion of several glands along its pathway however increases the amount of semen ejaculated.
The first gland that is activated, actually already before the ejaculation, initiated by the (preceding) sexual arousal, is the bulbo–urethral gland. Fluids from these two glands flow into the urethra and help lubricate this tract and the tip of the penis (which helps with its insertion into the vagina!).
Then the semen flows in the prostate where about an additional 30% of the semen fluid is added.
All these fluids contain a lot of chemicals and hormones that help and protect the transport of the germ cells into the vagina and the uterus of the female genital organs.
This is really the story of the development of the sperm, ultimately required to fertilize a female ‘egg’ which will lead to pregnancy and finally to the birth of a new human being.
The development of sperm cells, which occurs in the testes, is called spermatogenesis (“sperma” = sperm and “genesis” = birth).
It all starts with the development of the foetus and the birth of the little boy. When the boy is born, his testes already contain billions of spermatogonia, located in the walls of the seminiferous tubules, inside the testes.
Further development of these spermatogonia has to wait until the boy reaches puberty! Only then do the spermatogonia start to differentiate into a series of divisions until mature sperm cells are formed.
6.
After another few days, the secondary spermatocyte divides to produce two spermatids (still with 23 chromosomes each).
Since the female oocyte only contains XX chromosomes, the spermatids will determine, upon fusion, whether the new foetus will become a girl (XX) or a boy (XY)!
The testis does not only produce sperm cells but also other products, the most famous one of which is testosterone; the male hormone (although females also have a little of it!). Testosterone is produced by the Leydig cells, also located in the seminiferi tubuli.
This testosterone is required for the production of the testicles, the prostate and other typical mammalian characteristics such as body hair, muscle mass, bone structures etc.
So, finally we have a sperm cell! Actually, we have millions of them as the testes generate thousands of sperm cells every day.
The most important one is of course the nucleus, which contains half the genetic code for the new human being, including an X- or a Y-chromosome.
Behind the head is a space where the mitochondria are located. They provide the energy required for the tail (=flagella) to work when the sperm has to swim (in the female uterus).
Interestingly, at the front of the sperm cell, there is a structure, which looks like a cap; the “Acrosome”.
This acrosome contains several enzymes which will be required when the sperm tries to penetrate an egg cell.
The whole point of the male genital system is to deliver healthy sperm (and its chromosomes) to the woman!
For this, several steps have to take place:
- erection of the penis
- lubrication of the urethra
- orgasm
- ejaculation of the sperm
Erection (1) takes place by filling the two corpus cavernosum with blood. This is performed by more blood streaming into the two corpus cavernosum, located inside the penis. This is caused by the relaxation of the arteries leading to these two cavernosum, induced by nervous signals, which in turn are induced by erogenous stimuli!
As the penis is being erected:
- the prostate sphincter will be closed (to avoid urine leakage from the bladder)
- fluid is produced by the bulbourethral glands (2). This fluid is slightly basic to counter the acidic urine and provide a better environment for the sperm
- this fluid will also lubricate the tip of the penis glans to ease the “penetration” of the erected penis into the woman’s vagina.
Once the penis is erected, it can be inserted into the vagina of the woman and, when sufficiently stimulated, produce an orgasm. This orgasm induces the delivery of the sperm into the vagina.
After the addition of the fluid from the seminal vesicles, the sperm enters the urethra (6) and continues, still pushed by peristaltic contractions, towards the end of the penis where it finally “leaves” the male body and (hopefully) enters the female body!
There is something peculiar about the testicles. You know it is located in a bag, called a ‘scrotum’. The point I am trying to make is that the two testicles, and their surrounding scrotum, are located outside the body, below the abdomen. I believe this is the only organ located outside the body. Why?
In fact, when a male foetus is growing inside his mother, the embryonic testicles are located inside the abdomen of the foetus. But, right before the boy is born, the two testicles ‘descend’, from the abdomen, through the inguinal canal, into the scrotum, located outside of the body.
3.
Sometimes however, one or both testicles do not descend before birth. This condition is called “cryptorchidism” (link). If, in the few months after birth, the testicle(s) do not descend, then surgery must be performed to place the testicles in the scrotum. Why?
Hey! This is interesting! Apparently, the body temperature (normally at 37oC) is too high for proper sperm development! The sperm cells need a lower temperature for proper development.
In fact, if it gets very cold outside, something interesting may happen in man! Then, the smooth muscles inside the scrotal bag contract, thereby ‘lifting’ the testes closer to the body and to its warmer environment.
link: cryptorchidism: from Kryptos (=hidden) and Orchis (=testicle) Old Greek. Sounds difficult until you think of the word “cryptogram” (= hidden text)!
In both male and female genitalia, medical interventions are, for all kind of reasons, often performed or have been quite common.
For the male system, there are three often used medical interventions:
- Circumcision
- Sterilization
- Castration
In circumcision, the foreskin of the penis gland is removed. This is often performed in young boys for cultural or religious reasons.
Sometimes (rarely) a male suffers from phimosis (a condition when the foreskin is too narrow and can not be pulled back over the penis glands when the penis is erected). In that situation, circumcision can be helpful. Other wise, circumcision has no (medical) value.
Sterilization is performed when a male decides he want to be sterilized.
It is actually quite simple, cut or ligate the vas deferens in both testes. Under local anaesthesia, a cut is made through the scrotum, the vas deferens is pulled through the opening and cut, ligated and/or heated. That’s it! (This is called vasectomy; “vas” = “vas deferens” and “ectomy” = “to take out”)
Castration is the surgical removal of both testes from a male scrotum. This also makes the male sterile but, in addition, also has an effect on the hormones (such as testosterone), which then become much lower.
In old times, this was often done in males, often captives from a war, and were called eunuchs. If performed in young boys, this would stop or prevent the development of puberty; the formation of (pubic) hairs while their voices remained high!
