Maharashtra Board Class 11 Child Development Chapter 4 Prenatal Development and Care during pregnancy PDF Download

Prenatal Development And Care During Pregnancy

This chapter teaches you about how a baby develops from the time of conception until birth. Just like the life cycle of a butterfly begins as an egg, the life of a human being also begins as a fertilized egg. Now we will study in detail how individuals develop from the time of conception.

The period from conception to birth is referred to as the Prenatal period. Fertilization of an ovum (egg cell) by a sperm is the starting point of new life. The average length of prenatal period is 38 weeks from the date of conception. During this time a fertilized cell or zygote develops in a series of stages into a full term baby.

Conception

Meaning Of Fertilization And Conception

Fertilization

Fertilization is the process by which sperm and ova combine to create a single cell called a zygote. It occurs within 24 hours after the ovum descends to the tube. The sperms are contained in a fluid called semen. Semen is deposited at the neck of the uterus during intercourse. The sperms are drawn up into the fallopian tube by hormonal attraction and muscular contraction. The sperms secrete an enzyme which disperses the wall from around the ovum. Once it reaches the ovum it penetrates the cytoplasm. This leads to change in the membrane of the ovum in such a way that no other sperm can now enter it. The nuclear material in the head of the sperm now fuses with the nucleus of the ovum to get 46 chromosomes from both the parents. The cell then begins its mitotic division through the different stages of prenatal development. Fertilized ovum (zygote) slowly travels to uterus and moves for 5-6 days to get implanted into the walls of the uterus. This process is known as implantation. When implantation occurs it is called conception. A yolk sac is formed around the ovum cells till implantation process completes and it continues to nourish the ovum.

Teacher's Note

Fertilization happens when sperm and egg meet. Think of it like when your mom and dad come together to make you. It is a very important moment in life.

Exam Trick

Remember: Fertilization = Sperm + Egg = Zygote. Just like mixing two colors to make a new color, sperm and egg mix to make a zygote.

Points to Remember

Fertilization is when sperm and egg join together.
It happens in the fallopian tube.
A zygote is formed after fertilization.
The zygote then travels to the uterus.
Implantation means the zygote attaches to the uterus wall.

Importance Of Fertilization

Fertilization is most likely when intercourse happens 2 days before ovulation and a day after ovulation. This is so because the ova is capable of getting fertilized only for 24 hours after ovulation. Sperms also survive only for 12-48 hours in the female body. At the time of fertilization, few important factors such as i) heredity endowment ii) sex of the child iii) number of offsprings or children, are determined.

i) Heredity Endowment

This is an important factor that influences development right from the prenatal stage. It is the genetic endowment inherited from the biological parents at the time of fertilization. When ovum and sperm unite, they endow the baby-to-be (organism) with a genetic makeup that influences a wide range of characteristics such as colour of skin and hair, height, health, intellect.

ii) Sex Determination

The sex of the child is determined at the time of fertilization. The combination of chromosomes from both the parents will determine whether the foetus is a girl or a boy. When the X - Chromosome of the father combines with the X - Chromosome of the mother the foetus will be a girl. When the Y - Chromosome of the father combines with the X - Chromosome of the mother the foetus will be a boy.

iii) Number Of Offsprings

The important condition determined at the time of conception is whether the birth will be single or multiple. Singletons are children who are born alone. They may have siblings- brothers and sisters - but a period of nine months or more separate their birth from those of their siblings. The term 'multiple birth' refers to the birth of two or more babies within a few hours - twins, triplets.

There are two different types of twins: identical and fraternal.

Identical Or Uni-Ovular Twins

Identical twins come from a single ovum fertilized by a single sperm. As identical twins are formed from one fertilized ovum, they are of same sex i.e. both boys or both girls. They have the same genetic make up and similarities are observed among them.

Fraternal Or Non-Identical Twins

Two different sperms fertilize two ova released simultaneously. Such twins are called fraternal twins. They can be of same sex or different sex. Their genetic makeup will be different. Multiple birth i.e. having more than one child at the time of conception increases the possibility of premature birth and low birth weight. Proper care and nourishment of the pregnant woman should be ensured for a healthy baby and a safe delivery.

Teacher's Note

Identical twins look the same. Fraternal twins look different, like normal brothers or sisters. In India, we see many twin babies. Ask your parents if they know any twins.

Exam Trick

Remember: Identical = One egg, same look. Fraternal = Two eggs, different look. Just like one apple and two apples are different.

Points to Remember

Fertilization determines the sex of the baby.
Father's Y chromosome makes a boy.
Father's X chromosome makes a girl.
Identical twins come from one egg.
Fraternal twins come from two eggs.

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