Similar to the different endocrine glands that are generally overlooked till they start malfunctioning, the testes in males as well as the ovaries in females perform a vital function. The persistent or all-encompassing impact of these organs is especially evident when one is in his/ her adolescent stage, especially while the sex hormones heave and sexual evolution occurs. During no other period, perhaps barring the initial few years of one's life (interestingly, a good number of us actually do not bear much of those days in mind) does our body go through such remarkable as well as fast changes. In fact, the sex hormones have a greater impact than just our physical appearance and their power encompasses further than just the physiological processes related to sexual evolution and reproduction. In addition, the sex hormones have an influence over our emotions as well as mind-sets, as they bring in an entire range of cravings.
Sexual development starts immediately at the very fetal stage. Inside it, the fertilized egg carries all the genetic information that it may require even to make all types of cells throughout the life. Therefore, right from the beginning it is decided whether a particular embryo will grow up to be a male or a female. In fact, the sex organs start appearing in the very early stage of development of the fetus. While the testicles start appearing roughly in the seventh week of conception, the ovaries begin to develop from the sixteenth week. The levels of sex hormones are quite high during the development stage of the fetus. These hormones have a direct effect on the development of the sex glands of the fetus.
A number of medical specialists are of the view that this type of hormones, which are produced and secreted in the early stages, have an influence on the developing brain and are responsible for the differences in behavior among men and women. Other people, who may or may not be experts, are vehemently opposed to this view. The second group of people is of the view that it is the social issues, and not only the biological factors, that are entirely responsible for the dissimilarity in the manner in which men and women conduct themselves.
After baby's birth, there is a severe reduction in the amount of sex hormones a baby produces. However, scientists are yet to ascertain the precise role of sex hormones in children. While the testes as well as ovaries in children possess the aptitude to make as well as secrete hormones, their pituitary gland is yet to receive the signal to set off.
The testes or gonads of males are distinctly positioned. They are in a suspended position between the thighs and placed in a sac known as the scrotum. The main reason why the testes are located outside the male body is that they require lesser temperature to make sustainable sperm. The length of these sex organs - shaped like eggs, is roughly two inches, while their collective weight is below an ounce. The seminiferous (enclosing semen) tubules are basically extended, slender and curling tubes that are the location for the sperms to form. Making up about 95 per cent of the glands, the seminiferous tubes are firmly compressed inside the testes. The Leydig's cells (also known as interstitial cells of Leydig) are accommodated inside the small gaps between these tubes. These cells are responsible for manufacturing almost the entire androgen, counting testosterone - the main androgen hormone discharged from the testes.
The foremost function of the testes involves producing sperms. The seminiferous tubules within the testes are encircled by interstitial tissue (tissues present in the intervening spaces). A type of cells that have been named after the German scientist Franz Leydig lie inside the interstitial tissue. Luteinizing hormone released from the pituitary gland activates the cells of Leydig and they begin to synthesize testosterone hormone. Testosterone is made at the beginning of adolescence or puberty, which is considered to be the age when sexual maturity occurs. Testosterone also helps in developing the secondary sexual personality in males, for instance, beard, moustache, body hair and others.
As mentioned earlier, the testes are placed within the scrotum, keeping them outside the body of the males. This is vital considering the fact that the best possible temperature at which sperm should be maintained is roughly 95�F. On the other hand, the normal temperature of our body is 98.6�F.
Within both the testes there are several hundred seminiferous tubules that are encircled by connective tissues as well as interstitial cells. The network of the tubules inside the testis is connected with the epididymis that is positioned resting on each testis. As mentioned earlier, the seminiferous tubules are the place where the sperm cells are produced. However, they are not mature till they are carried into the epididymis.
The interstitial cells make all the androgen hormones, including testosterone - the most prominent sex hormone in males.
As the testes are located outside the male body, they are further susceptible to blunt suffering. The blood vessels inside a testis (also known as torsion) have the ability to constrict, and at times, the interstitial cells also do not make sufficient amount of testosterone (a condition called hypogonadism). In addition, cancer of the testicles is a life-threatening condition.
In the case of females, the ovaries are the gonads. Each ovary is positioned on either side of the uterus and is bound to the uterus by means of ligaments. The shape of the ovaries is oval and they are about 0.5 inches in length. The weight of the ovaries may differ in different phases in the life of a female, but it is of maximum weight during the fertility years of a female. Several hormones like estrogen, progesterone as well as relaxin are produced by the ovaries. At the time of birth, the ovaries enclose the entire follicles or the cells that form eggs that the female will produce all through her life. It is believed that females start with as many as two million egg-forming cells or follicles. Of these, just a solitary follicle is used every month for developing a mature egg.
Similar to the hormones produced by the adrenal cortex, even the hormones produced by the sex glands are basically steroids. While they have a common carbohydrate source, the final form as well as the function of the hormones produced by the adrenal cortex and the sex glands are significantly different. Every gland encloses specific enzymes, which are responsible for synthesizing particular steroids. The hypothalamus and pituitary glands govern the hormones produced and secreted by the gonads.
The endocrine system of the females comprises the gonads, but the main purpose of the gonads is gamete (egg) production.
The ovary contains several immature ova and every time just a single ovum is set aside for becoming mature. The follicle cells encircle every ovum in a specific manner. After an ovum matures and is on the verge of being released, a number of the related cells discharge the female hormone called estrogen. This female hormone results in heat or estrous and results in alterations in the body of a female. One such change is breast development.
After the release of the ovum (a process called 'ovulation'), the cells associated within stay back inside the ovary and wait for receiving a news or signal. If there is news that the released ovum has already been fertilized and connected with the uterus (in other words, materialization of pregnancy), these associated cells spring into action. Then these cells start secreting two hormones - progesterone and relaxin. In turn, these two hormones result in certain alterations in the pregnant female's body. In the event of the ovum not being fertilized, which is the case most often, the associated cells do not secrete progesterone and relaxin.