It was once proposed that we, as humans, are only born to reproduce, and that perpetuation of the species is the final goal of every species in the world. All our systems are adapted to first fulfill this primary goal. We are basically born to give birth to new young ones, so that they can give birth to more new young ones. Why we need to continue this cycle borders on the philosophical, so let’s leave that aside for now. For a change, let’s try to understand the system of our body that directly performs this function – the reproductive system.
The male and female reproductive systems differ from each other, as they have different functions. Males need to produce and store sperm in large numbers, while females need to produce a limited number of eggs and accommodate the growing fetus for roughly 9 months, making space in their body for that.
Male Reproductive System
This system involves the parts that produce and store the sperm, those which produce other secretions to form the ejaculatory fluid, and the parts required for the transmission of sperm into the female.
Sperm are produced and stored in the testes. These are paired organs that are suspended in a sac-like structure called the scrotum. This hangs outside the body so as to maintain the temperature 2-3 degrees lower than the body temperature. In summer, the scrotum hangs lower, while in winters it moves closer to the body to maintain its ideal temperature.
The testes are covered by a membranous covering called the tunica albuginea. Inside it are the seminiferous tubules. These are long, coiled tubules separated into lobes. There may be up to 900 lobules in each testicle, with each lobule having 1-4 seminiferous tubules. These tubules are lined with germ cells, which eventually mature to form sperms. This process is aided by the Sertoli cells, which form the epithelium of the seminiferous tubules. Packaged between these tubules are cells known as Leydig cells. These cells are responsible for the production of testosterone and other androgens.
The sperm that are produced are collected by the rete testis, which transfer them to the efferent ducts. These then empty their content into the epididymis. The epididymis stores the sperm cells while they mature. It then carries them up to the vas deferens, which takes them to the urethra via the ejaculatory duct. Males also urinate through the urethra. The copulatory organ for males is the penis.
Along the way, the sperm are enhanced by the secretions from the seminal vesicles, prostate gland and Cowper’s gland. The seminal vesicle secretion helps to maintain an alkaline pH that can survive the acidic pH of the vagina. It also contains fructose, which helps in the nourishment and survival of the sperm for up to 1 week. The prostate gland secretion contains enzymes and proteins that help to protect the sperms, while the Cowper’s gland secretes a milky, alkaline fluid to neutralize the acidic environment caused by the leftover urine in the urethra.
Female Reproductive System
The main female reproductive system consists of a pair of ovaries, the Fallopian tubes, uterus, cervix and vaginal opening. Located in the abdominal region, the uterus is a pear-shaped organ. On either side, it has an ovary, which is connected to the uterus by the Fallopian tubes. The immature eggs are formed in the female while she is a fetus. Upon sexual maturity, every month, one egg matures and is released by the ovary. Each ovary usually alternates releasing an egg every month. The egg travels down the Fallopian tube and moves into the uterus. Every month, the uterus prepares for a baby, thus causing the thickening of the lining of the uterine wall. When no fertilization takes place, this lining is shed, thus causing ‘periods’ or menstruation.
The menstrual cycle refers not just to the shedding of the lining, but to the whole monthly process of the maturation of the egg, its release, the fluctuations of the hormones, and the eventual lining of the thickened uterine wall. The female hormones, oestrogen and progesterone, play vital roles in the maintenance of this periodic cycle.
When the sperm enters the body of the female, it is essential that the fertilization take place in the Fallopian tubes. Once the egg is fertilized by the sperm, the zygote, as it is now called, travels down to the uterus where it attaches or implants in the wall of the uterus. Once this implantation has occurred, the female is said to be pregnant.
While an impaired reproductive system doesn’t endanger an individual, it is absolutely essential in terms of the propagation of the species. In humans, such an inability to reproduce often leads to certain types of social stigma, but that unfortunate state of affairs is far beyond the scope of this article!