Human reproductive System

The UPSC mains GS-3 paper syllabus has various subjects like Economics, Science and Technology. Science and technology in UPSC is mostly concerned with current Affairs. but it is necessary to understand the basics of science. Human Body consists of some of the most complex systems. The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system.

TOPICS

What is Digestive system
Parts & Functions of Digestive System
Functions of Digestive system

WHAT IS REPRODUCTIVE SYSTEM

The human reproductive system includes the male reproductive system which functions to produce and deposit sperm; and the female reproductive system which functions to produce egg cells, and to protect and nourish the fetus until birth. Humans have a high level of sexual differentiation

MALE REPRODUCTIVE SYSTEM

The male has reproductive organs, or genitals, that are both inside and outside the pelvis. The male genitals include:

the testicles
the duct system, which is made up of the epididymis and the vas deferens
the accessory glands, which include the seminal vesicles and prostate gland
the penis

The testicles are also part of the endocrine system because they make hormones, including testosterone Testosterone is a major part of puberty in guys. As a guy makes his way through puberty, his testicles produce more and more of it. Testosterone is the hormone that causes boys to develop deeper voices, bigger muscles, and body and facial hair. It also stimulates the production of sperm.

Alongside the testicles are the epididymis and the vas deferens, which transport sperm. The epididymis and the testicles hang in a pouch-like structure outside the pelvis called the scrotum. This bag of skin helps to regulate the temperature of testicles, which need to be kept cooler than body temperature to produce sperm. The scrotum changes size to maintain the right temperature. When the body is cold, the scrotum shrinks and becomes tighter to hold in body heat. When it's warm, it gets larger and floppier to get rid of extra heat. This happens without a guy ever having to think about it. The brain and the nervous system give the scrotum the cue to change size.

The accessory glands, including the seminal vesicles and the prostate gland, provide fluids that lubricate the duct system and nourish the sperm. The urethra is the channel that carries the sperm (in fluid called semen) to the outside of the body through the penis. The urethra is also part of the urinary system because it is also the channel through which pee passes as it leaves the bladder and exits the body.

The penis is actually made up of two parts: the shaft and the glans. The shaft is the main part of the penis and the glans is the tip (sometimes called the head). At the end of the glans is a small slit or opening, which is where semen and pee exit the body through the urethra. The inside of the penis is made of a spongy tissue that can expand and contract.

FEMALE REPRODUCTIVE SYSTEM

The external part of the female reproductive organs is called the vulva, which means covering. Located between the legs, the vulva covers the opening to the vagina and other reproductive organs inside the body.

The fleshy area located just above the top of the vaginal opening is called the mons pubis. Two pairs of skin flaps called the labia (which means lips) surround the vaginal opening. The clitoris, a small sensory organ, is located toward the front of the vulva where the folds of the labia join. Between the labia are openings to the urethra (the canal that carries pee from the bladder to the outside of the body) and vagina. When girls become sexually mature, the outer labia and the mons pubis are covered by pubic hair.

A female's internal reproductive organs are the vagina, uterus, fallopian tubes, and ovaries.

The vagina is a muscular, hollow tube that extends from the vaginal opening to the uterus. Because it has muscular walls, the vagina can expand and contract. This ability to become wider or narrower allows the vagina to accommodate something as slim as a tampon and as wide as a baby. The vagina's muscular walls are lined with mucous membranes, which keep it protected and moist.

The vagina serves three purposes:

It is the route for the penis during coitus
It's the pathway (the birth canal) through which a baby leaves a woman's body during childbirth.
It's the route through which menstrual blood leaves the body during periods.

A very thin piece of skin-like tissue called the hymen partly covers the opening of the vagina. Hymens are often different from female to female. Most women find their hymens have stretched or torn after their first sexual experience, and the hymen may bleed a little (this usually causes little, if any, pain). Some women who have had sex don't have much of a change in their hymens, though. And some women's hymens have already stretched even before they have sex.

The vagina connects with the uterus, or womb, at the cervix (which means neck). The cervix has strong, thick walls. The opening of the cervix is very small (no wider than a straw), which is why a tampon can never get lost inside a girl's body. During childbirth, the cervix can expand to allow a baby to pass.

The uterus is shaped like an upside-down pear, with a thick lining and muscular walls — in fact, the uterus contains some of the strongest muscles in the female body. These muscles are able to expand and contract to accommodate a growing fetus and then help push the baby out during labor. When a woman isn't pregnant, the uterus is only about 3 inches (7.5 centimeters) long and 2 inches (5 centimeters) wide.

At the upper corners of the uterus, the fallopian tubes connect the uterus to the ovaries. The ovaries are two oval-shaped organs that lie to the upper right and left of the uterus. They produce, store, and release eggs into the fallopian tubes in the process called ovulation

There are two fallopian tubes, each attached to a side of the uterus. Within each tube is a tiny passageway no wider than a sewing needle. At the other end of each fallopian tube is a fringed area that looks like a funnel. This fringed area wraps around the ovary but doesn't completely attach to it. When an egg pops out of an ovary, it enters the fallopian tube. Once the egg is in the fallopian tube, tiny hairs in the tube's lining help push it down the narrow passageway toward the uterus.

Female reproductive system has two functions –

Production of female gamete called ovum/egg.
Providing nutrition and protecting the developing embryo.

During puberty, eggs in the ovaries start to mature. One of the ovaries releases the matured ovum in every 28 to 30 days and is called ovulation.

Menstrual Cycle

All females, after reaching their puberty produce mature egg cell every month during a process called the menstrual cycle. During this period, an ovary discharges a mature egg, which travels to the uterus. In the uterus, if the egg is not fertilized, the lining in the uterine sheds away and a new cycle begins. Overall a menstrual cycle lasts for 28 days, in some cases, these cycles may either last for 21 days or as long as 35 days in some individuals. The entire process of the menstrual cycle is controlled by the endocrine system and the hormones involved are FSH, LH, estrogen, and progesterone. Both FSH and LH hormones are produced by the pituitary gland, whereas estrogen and progesterone hormones are produced by the ovaries.

Alon with the hormonal disorders, there are many other factors, which are responsible for the disturbance in the menstrual cycle. The responsible factors include diet, exercise, stress and weight gain or loss affects the menstrual cycle. The cycle may be irregular at times, especially during puberty. The menstrual cycles occur every month from the time of puberty up to the age of 45 to 55, except during pregnancy. After the age of 55 ovaries slows down their production of hormone and release of mature eggs. Progressively, the menstrual cycle stops, therefore, the woman is no longer able to become pregnant.

Estrogen and Progesterone

Estrogen and progesterone hormones are produced by the ovaries that foster the development of reproductive organs by maintaining the proper uterine cycle and by developing female secondary sex characteristics. During menopause, usually between age 45 and 55, the uterine cycle stops, and the ovaries are no longer produce estrogen and progesterone hormones.

Infertility
In general, infertility can be defined as the failure in couples of not getting pregnant, despite having carefully timed, unprotected sex for one year. It is estimated to be around 15% of all couples undergo infertility. The reasons behind this infertility in males and females are-

In Females:

Blocked oviducts.
Endometriosis.

In Males:

Low sperm count.
Sperm abnormalities.

DEVELOPMENT OF EMBRYO

About 5 to 6 days after the sperm fertilizes the egg, the fertilized egg has become a multicelled blastocyst. A blastocyst is about the size of a pinhead, and it's a hollow ball of cells with fluid inside. The blastocyst burrows itself into the lining of the uterus, called the endometrium. The hormone estrogen causes the endometrium to become thick and rich with blood. Progesterone, another hormone released by the ovaries, keeps the endometrium thick with blood so that the blastocyst can attach to the uterus and absorb nutrients from it. This process is called implantation.

As cells from the blastocyst take in nourishment, another stage of development begins. In the embryonic stage, the inner cells form a flattened circular shape called the embryonic disk, which will develop into a baby. The outer cells become thin membranes that form around the baby. The cells multiply thousands of times and move to new positions to eventually become the embryo .

After about 8 weeks, the embryo is about the size of a small berry, but almost all of its parts — the brain and nerves, the heart and blood, the stomach and intestines, and the muscles and skin — have formed.

During the fetal stage, which lasts from 9 weeks after fertilization to birth, development continues as cells multiply, move, and change. The fetus floats in amniotic fluid inside the amniotic sac. The fetus gets oxygen and nourishment from the mother's blood via the placenta . This disk-like structure sticks to the inner lining of the uterus and connects to the fetus via the umbilical cord. The amniotic fluid and membrane cushion the fetus against bumps and jolts to the mother's body.

Pregnancy lasts an average of 280 days — about 9 months. When the baby is ready for birth, its head presses on the cervix, which begins to relax and widen to get ready for the baby to pass into and through the vagina. Mucus has formed a plug in the cervix, which now loosesn. It and amniotic fluid come out through the vagina when the mother's water breaks.

When the contractions of labor begin, the walls of the uterus contract as they are stimulated by the pituitary hormone oxytocin . The contractions cause the cervix to widen and begin to open. After several hours of this widening, the cervix is dilated (opened) enough for the baby to come through. The baby is pushed out of the uterus, through the cervix, and along the birth canal. The baby's head usually comes first. The umbilical cord comes out with the baby. It's clamped and cut close to the navel after the baby is delivered.

The last stage of the birth process involves the delivery of the placenta, which at that point is called the afterbirth. After it has separated from the inner lining of the uterus, contractions of the uterus push it out, along with its membranes and fluids.

Human reproductive System