Human Reproduction

• Human reproduction is any form of sexual reproduction resulting in human fertilization.
• The reproductive system is a system of organs that takes part in this process.
• Humans are sexually reproducing and viviparous.
• The rate of reproduction is slower in sexual reproduction.
• Humans are unisexual.
• The reproductive events in humans include the formation of gametes (gametogenesis), i.e., sperms in males and ovum in females, transfer of sperms into the female genital tract (insemination), and fusion of male and female gametes (fertilization) leading to the formation of zygote.
• This is followed by the formation and development of blastocyst and its attachment to the uterine wall (implantation), embryonic development (gestation), and delivery of the baby (parturition).
• The beginning of sexual maturity or the ability to reproduce is known as puberty. Puberty occurs at the age of 10 - 14 years in girls and 13 - 15 years in boys.
• There are remarkable differences between the reproductive events in the male and in the female, for example, sperm formation continues even in old men, but the formation of ovum ceases in women around the age of fifty years.
• The reproductive system of each sex consists of many organs. The latter is distinguishable into primary and secondary sex organs. Besides these, there are some accessory sex characters.

1. Primary sex organs: Primary sex organs are also called gonads which form gametes like - testis in males and ovary in females. Testis produces sperms and secretes testosterone. The ovary produces ova and secretes estrogen. The male gamete is a spermatozoon. The female gamete is the ovum.
2. Secondary sex organs: Sex organs, glands, and ducts which do not produce gametes but are otherwise essential for sexual reproduction are known as secondary sex organs. In males, these include the epididymis, vas deferens, seminal vesicles, prostate, bulbourethral glands, penis, etc. In females, these organs are the fallopian tube, uterus, vagina, Bartholin gland, etc.
3. Accessory / External / Secondary sex characters: These are traits which do not have any direct role in reproduction but provide specific features and structures to both sexes.

Humans use sexual mode of reproduction.

-Sexual maturation: The period of life when production of germ cells i.e. Ova (female) and sperm (male) start in the body. This period of sexual maturation is called puberty.

Changes at puberty:-

Male and females:-

-Thick hair growth in armpits and genital areas.

-Skin becomes oily, may result in pimples.

In females:-

-Breast size increases

-Girls begin to menstruate.

In males:-

-Thick hair growth on face

-voice begins to crack

These changes signal that sexual maturity is taking place

MALE REPRODUCTIVE SYSTEM:-

(i)Testes:-

-A pair of testes are located inside the scrotum which is present outside the abdominal cavity.

-scrotum has a relatively lower temperature needed for the production of sperms.

-male germ cell i.e. sperms are formed here.

-testes release male sex hormone (testosterone)

Functions:-

-regulate production of sperms.

-bring changes at puberty.

(ii) Vas deferns:

- It passes the sperm from the testes to the urethera.

(iii Urethera:-

- it is a common passage for both sperm and urine.

(iv) Associated gland:-

- Seminal vesicles and prostate gland add their secretion to the sperms. This fluid provides nourishment to sperms and make their transport easy.

- sperm along with secretion of glands form semen.

FEMALE REPRODUCTIVE SYSTEM:

(i) Ovary

- A pair of ovary is located at both sides of the abdomen.

- Female germ cell i.e. eggs are produced here.

- At the time of birth of a girl, thousand of immature eggs are present in the ovary

- At the onset of puberty, some of these eggs start maturing.

- One egg is produced every month by one of the ovaries.

(ii) Oviduct or Fallopian tube:-

- Receives the egg produced by the ovary and transfer it to the uterus.

- Fertilization i.e. fusion of gametes takes place here.

(iii) Uterus

- It is a bag like structure where development of the baby takes place

- uterus opens into vagina through cervix.

FERTILISATION OF EGG:-

- The fertilized egg called zygote is planted in uterus and develops into an embryo.

- The embryo gets nutrition from the mothers blood with the help of special tissue called placenta. It provides a large surface area for the exchange of glucose, oxygen and waste material.

- The time period from fertilization upto the birth of the baby is called gestation period.

WHEN EGG IS NOT FERTILISED:-

- The uterus prepares itself every month to receive fertilized egg

-The lining of the uterus becomes thick and spongy, required to support the embryo.

-When fertilisation had not taken place this lining is not needed any longer.

-This lining breaks and comes out through the vagina as blood and mucus.

-this cycle takes around 28 days every month and is called menstruation.

IMPLANTATION: In humans, implantation is the stage of pregnancy at which the embryo adheres to the wall of the uterus. At this stage of parental development, the conceptus is called a blastocyst. It is by this adhesion that the embryo receives oxygen and nutrients from the mother to be able to grow.

PLACENTA: The placenta is an organ that develops in the uterus during pregnancy. This structure provides oxygen and nutrients to the growing baby and removes waste products from the baby's blood. The placenta attaches to the wall of the uterus, and the baby's umbilical cord arises from it. The organ is usually attached to the top, side, front or back of the uterus. In rare cases, the placenta might attach in the lower uterine region (placenta previa).

GESTATION: Gestation, in mammals, the time between conception and birth, during which the embryo or fetus is developing in the uterus.

PARTURTION: The act or process of giving birth is known as parturtion.