Reproduction in Humans

The male reproductive system of human beings consists of a pair of testes, sperm ducts, urethra, penis and accessory glands. Each of them is briefly described below:

1. Testes — Testes are located outside the abdomen in a sac-like structure called scrotum. They are the primary reproductive organs of the male reproductive system. They produce the male gametes called sperms.
2. Sperm Ducts — The sperms produced in the testes, travel through the sperm duct or vas deferens to reach the urethra.
3. Accessory Glands — As the sperms pass through the sperm duct, secretions from the accessory glands are mixed with them. This mixture is called semen.
4. Urethra — It is a tube through which urine and semen passes.
5. Penis — Through penis, sperms are discharged and deposited into the vagina of the female body. In males, the penis is the organ used both for the discharge of the urine and the sperms.

In human beings, fertilization takes place in the fallopian tubes or oviducts inside the female body. The sperms from the male received by the vagina swim up to the oviduct for fertilization. An ovum is fertilized by a single sperm. It results in the formation of a single cell called zygote. Since the zygote is formed as a result of the fusion of sex cells from the father and mother, it has the chromosomes and genes from both of them. Thus, the new individual inherits characteristics from both the parents. Zygote moves from the oviduct to the uterus and gets implanted in it for further development. The below diagram shows the process of fertilization in human beings:

The formation of an individual from the zygote is called development. In human beings, the zygote undergoes continuous cell division to form a ball of cells. The ball gets implanted in the uterine wall for further development. The implanted ball of cells undergoes many cell divisions. The cells change their size, shape and function to become different types of cells such as nerve cells and blood cells. From these, tissues and organs develop and get organized into various organ systems of the baby. From the third week of development till the end of the second month, the developing organism is referred to as the embryo. From the third month until birth, it is called foetus.

The structure which connects the foetus to the uterus and helps the foetus to get oxygen and nutrients from mother is called placenta. Placenta is an organ attached to the lining of the uterus.

The placenta is beneficial to the foetus in following ways:

1. The developing foetus receives essential nutrients and oxygen from the mother.
2. Carbon dioxide and other wastes from the foetus also pass into the mother's blood through the placenta.

The fusion of male and female gametes i.e. sperm and ova, either inside or outside the body of the female is called Fertilization.

The male reproductive organs of human beings are

1. a pair of testes
2. sperm ducts
3. urethra
4. penis
5. accessory glands

Penis is the male reproductive organ through which sperms are released.

The mixture of the sperms and secretions from the accessory glands is called semen.

Ovaries produce ova.

Fallopian tube or Oviduct.

From the third month of development until birth, the developing organism in the uterus is known as Foetus.

The structure which connects the foetus to the uterus and helps the foetus to get oxygen and nutrients from mother is called placenta.

A zygote is formed as a result of fertilization.

The male gametes are called sperm.

The sperm travel through the sperm duct or vas deferens to reach the urethra.

The ovaries are almond-sized oval glands situated in the pelvic or hip region.

The cervix is narrow and opens to the outside through a muscular tube called the vagina.

Human fertilization occurs in the fallopian tube and the baby develops in the uterus.

The foetus is connected to the uterus by a structure called placenta.

Amniotic fluid acts like a cushion and protects the developing foetus in the uterus.

From the third week of development till the end of the second month, the developing organism is referred to as the embryo.

The time period between fertilization and birth is called gestation.

The completed table is shown below:

oviducts → ovaries

uterus → fallopian tube or oviduct

vagina → uterus

ovary → vagina

Ovulation — The release of a mature egg from an ovary is called ovulation.

Menstruation — Discharge of blood along with the broken lining of uterine tissues in females is called Menstruation.

Fertilization — The fusion of male and female gametes i.e. sperm and ova, either inside or outside the body of the female is called Fertilization.

Foetus — From the third month of development until birth, the developing organism in the uterus is known as Foetus.

When an ovum fuses with a sperm outside the body, it is called external fertilization.

Testes produce male sex hormone called testosterone.

Fertilization of the ovum takes place in the fallopian tubes.

The females have 28 day-long reproductive cycle called menstrual cycle.

The embryo is attached to the uterus by a structure called placenta.

1. The labelled diagram is shown below:

2. Testosterone
3. Testes are located outside the abdomen in a sac-like structure called scrotum.

The Correct sequence is as follows:

1. ovulation
2. fertilization
3. implantation
4. embryonic development
5. birth

No, menstruation and ovulation does not occur during pregnancy. As the embryo gets implanted into the uterus, the uterine wall is not shed so menstruation does not occur. Also, ovary does not release a new egg during pregnancy so ovulation does not occur.

frogs

Reason — External fertilization is seen in aquatic habitats, for example in fishes and frogs.

testes

Reason — Sperms are produced in a pair of special reproductive organs called testes.

scrotum

Reason — Testes are located outside the abdomen in a sac-like structure called scrotum.

sperm duct

Reason — The sperms travel through the sperm duct or vas deferens to reach the urethra.

ovulation

Reason — The release of a mature egg from an ovary is called Ovulation.

fallopian tubes

Reason — Fertilization takes place in the fallopian tubes or oviducts of the human females.

embryo

Reason — From the third week of development till the end of the second month of pregnancy, the developing organism is called embryo. From the third month until birth, it is called foetus.

progesterone and oestrogen

Reason — The two main functions of ovaries are to produce eggs or ova and secrete female sex hormones progesterone and oestrogen.

False

Corrected Statement — Sexual reproduction involves the fusion of an egg and a sperm.

False

Corrected Statement — The ovum is carried from the ovary to the uterus by the fallopian tubes or oviduct.

True

False

Corrected Statement — Normally, one egg is released from one of the ovaries every month.

True