The reproductive system is necessary for the production of new living organisms. The ability to reproduce is a basic characteristic of life. In sexual reproduction, two individuals produce offspring that have genetic characteristics from both parents. The primary function of the reproductive system is to produce male and female sex cells and to ensure the growth and development of offspring. The reproductive system is comprised of male and female reproductive organs and structures. The growth and activity of these organs and structures are regulated by hormones. The reproductive system is closely associated with other organ systems, particularly the endocrine system and urinary system.
Both male and female reproductive organs have internal and external structures. Reproductive organs are considered to be either primary or secondary organs. The primary reproductive organs are the gonads (ovaries and testes), which are responsible for gamete (sperm and egg cell) and hormone production. The other reproductive structures and organs are considered secondary reproductive structures. Secondary organs aid in the growth and maturation of gametes and developing offspring.
A woman’s reproductive system is a delicate and complex system in the body.
The reproductive system can be impacted by a number of diseases and disorders. This includes cancer that may develop in reproductive organs such as the uterus, ovaries, testicles, or prostate. Disorders of the female reproductive system include endometriosis (endometrial tissue develops outside of the uterus), ovarian cysts, uterine polyps, and prolapse of the uterus. Disorders of the male reproductive system include testicular torsion (twisting of the testes), hypogonadism (testicular under-activity resulting in low testosterone production), enlarged prostate gland, hydrocele (swelling in the scrotum), and inflammation of the epididymis.
The male reproductive system consists of sexual organs, accessory glands, and a series of duct systems that provide a pathway for fertile sperm cells to exit the body. Male reproductive structures include the penis, testes, epididymis, seminal vesicles, and prostate gland.
Similarly, the female reproductive system contains organs and structures that promote the production, support, growth, and development of female gametes (egg cells) and a growing fetus.
Gametes are produced by a two part cell division process called meiosis. Through a sequence of steps, the replicated DNA in a parent cell is distributed among four daughter cells. Meiosis produces gametes with one half the number of chromosomes as the parent cell. Because these cells have one half the number of chromosomes as the parent cell, they are called haploid cells. Human sex cells contain one complete set of 23 chromosomes. When sex cells unite at fertilization, the two haploid cells become one diploid cell that contains 46 chromosomes.
The production of sperm cells is known as spermatogenesis. This process occurs continuously and takes place in the male testes. Hundreds of millions of sperm must be released in order for fertilization to take place. Oogenesis (ovum development) occurs in the female ovaries. In meiosis I of oogenesis, daughter cells are divided asymmetrically. This asymmetrical cytokinesis results in one large egg cell (oocyte) and smaller cells called polar bodies. The polar bodies degrade and are not fertilized. After meiosis I is complete, the egg cell is called a secondary oocyte. The haploid secondary oocyte will only complete the second meiotic stage if it encounters a sperm cell and fertilization begins. Once fertilization is initiated, the secondary oocyte completes meiosis II and is then called an ovum. The ovum fuses with the sperm cell, and fertilization is complete. The fertilized ovum is called a zygote.