What is meant by Human Reproduction?

Reproduction defines a biological process that brings new offspring into life from the parents. In humans, reproduction is the process by which gametes from both male and female parents’ gonad fuse to produce a fetus in the female’s body (uterus). The male and female have different mechanisms of producing sex cells or gametes. The male provides sperms, whereas the female provides the egg. Humans have a high degree of sexual differentiation. In addition to reproductive systems, the secondary characteristics also vary in both males and females. The reproductive organ in males is the testis, and the reproductive organ in females is the ovary. Reproduction forms the basis of the existence of life in the world. Every organism has to reproduce to survive. The two methods which prevail universally are asexual and sexual. Sexual methods need two parents’ gametes, usually male and female, to reproduce. An asexual method is usually satisfied by a single parent. In humans, sexual reproduction takes place.

Structure of the Reproductive System

Female reproductive system

A series of organs are found in the female reproductive system, placed in the pelvic region. The female reproductive system has three main parts: vulva, vagina, and uterus. Breasts are not considered part of the reproductive system but are part of the parenting stage.

The vulva is outside the vagina, including the clitoris, labia, and urethra. Bartholin’s gland secretes mucus during intercourse to lubricate the vulval region. The cervix connects the vagina to the uterus, and the fallopian tubes connect the ovaries to the uterus. There are two ovaries in a female, out of which usually one produces an egg alternatively. Thousands of immature eggs are present in the ovaries that eventually mature and fertilize.

The pituitary gland releases a hormone that triggers the maturation of the ovum. This ovum passes through the fallopian tube to the uterus. The ovum is brought into the uterus with full preparations, including endometrial lining on the uterus walls. Suppose the ovum is not fertilized by a sperm in the fallopian tube or near to the uterus; the ovum shreds off and causes the blood to exit the body, which forms the menstrual cycle in females. This cycle takes 28 days on average in normal and healthy females.

Male reproductive system

The male sex organs are located outside the body around the pelvis region. The only function of the male reproductive system is to provide mature sperm for fertilization. The organs required in the process of getting a mature sperm are divided into three categories. First, the testis produces spermatozoa and stores them. The testis is located in the scrotum, a temperature-regulating organ. The immature spermatozoa travel to the epididymis for further development. Second, certain fluid-producing glands like Cowper’s gland, prostate, vas deferens, and seminal vesicles release their secretions into the spermatozoa. Third, the parts involved in intercourse and deposition of sperm inside the female vagina are the penis, vas deferens, and urethra.

The testis releases certain hormones under the control of the pituitary gland for the development of sperms. These hormones also regulate the primary and secondary characteristics in males, like deep voice and facial hairs.

Gametes

Production of gametes in females

In females, the formation of gametes within the gonads occurs through gametogenesis. The germ cells undergo meiosis to convert diploid chromosomes to haploid from 46 (diploidy) to 23 (haploidy) chromosomes. Gametogenesis in females is called oogenesis. Oogenesis occurs in the ovarian follicles. The ovary has an immature ovum called primary oocyte, which is present since the birth of a female. This immature ovum has a single layer of cells called follicles. After puberty, when the egg starts to mature, the follicles divide rapidly and become larger, called secondary follicles. One dominating follicle becomes mature, and that particular egg is released into the fallopian tube. The hormones estrogen and progesterone levels prepare the uterus lining. If the egg gets fertilized in the fallopian tube, the pregnancy is conceived in the uterus. But if the egg does not get fertilized, the egg continues to travel to the uterus and shreds off. The endometrial lining shreds off with the egg, releasing blood through the vagina, a process referred to as the menstrual cycle.

Production of gametes in males

Spermatogenesis is the name of gametogenesis in males. It takes place after puberty in the seminiferous tubules of the testis. The spermatozoa (immature sperm cells) are sent to the epididymis, where they gain motility by adding a tail. Each primary spermatocyte forms four functional gametes. These gametes (sperms) travel down to the vas deferens. Then the sperm cells arrive at the ampulla, above the prostate gland, where the secretions from the seminal vesicle are added. The seminal vesicle is placed next to the ampulla. The seminal fluid, along with the sperm, travels to the ejaculatory ducts and then the urethra. When the sperms cross the prostate gland, a milky fluid is added to the seminal fluid, producing semen. The semen is then ejaculated from the penis through the urethra. The production of sperm cells needs a temperature of 3º below the body temperature. The scrotum maintains this temperature as it lies outside the body.

Diseases

The organs in the body can anytime undergo some malfunctioning, leading to diseases and disorders. The main reproductive diseases found in humans are genetic abnormalities, infections, cancers, and environmental, physical, and psychological problems that lead to infertility.

The genetic abnormality can lead to Turner syndrome, cystic fibrosis, and Klinefelter syndrome. The cancers are usually found in females, like cervical cancer. The other psychological and physical problems such as stress, accident, sudden shock can lead to infertility or abnormality. These conditions can be treated by various methods and with proper doctor consultations.

Birth Control

Pregnancy in women can sometimes be unwanted and can be controlled through birth control methods. These methods can be physical, chemical, or surgical (permanent). The most commonly used is the condom which protects the sperms from being ejaculated in the female reproductive tract. The other methods used are copper T, cervical cap, contraceptive pills, intrauterine devices. These birth control techniques do not ensure 100% safety but can prevent pregnancy up to a good percentage. They also protect against sexually transmitted diseases (STDs). The permanent method is vasectomy and tubectomy in males and females, respectively. These two are the safest methods to avoid pregnancy but are irreversible.

Common Mistakes

• Females are born with sex cells that are present as immature eggs in their ovaries. The eggs only get matured after puberty.
• Breasts are not included in the reproductive system but are part of the parenting stage of reproduction.

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for

• Bachelors of Science in Biology
• Master of Science in Zoology
• Bachelor of Medicine and Bachelor of Surgery

Related Concepts

1. Infertility
2. Childbirth control methods
3. Cervical cancer