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Q.2. List three stages of pre-natal development and discuss the important developmental events that occur during each stage.

Development : it is defined as the lifelong process of change
Or
It may be defined as physical, psychological and cognitive changes taking place throughout the life span.

Conception:
As a result of sexual intercourse, millions of sperms are introduced into the female body. They swim towards ova, female gamete. As one of the sperm fuses with ova, electric shock is given off which prevents other sperms from fusing. this results in the formation of zygote.
Following conception i.e fusion of male gamete with female ova, a zygote undergoes three stages namely
• Germinal stage
• Embryonic stage
• Foetal stage

Germinal stage : lasting from conception till two week stage is called the germinal stage. This stage ends up with the establishment of placenta. Neural tube starts to develop which later forms brain and spinal cord.

Embryonic stage: from two weeks to eight week stage is known as embryonic stage. At third week stage eyes formation occurs, at fourth week arm and leg buds are formed. Heart starts beating. In embryonic stage, all the important developmental organs complete their formation.

Fetal stage: it lasts from two months till the end of pregnancy. In this stage, completed organs start their functioning. Throughout, the developmental period a fetus receives all the necessary nutrients and gases from his mother through placenta. at the start, a foetus is only 3-4 inches in size but it grows as much as 20 inches in size till the completion of this stage.

development

4 weeks/1 month
• 1\10 th of an inch
• Zygote is protected in an amniotic sac
• Development of neural tube, brain, digestive system starts
• It is known as zygote

8 week
• 1 inch size
• Development of hands and feet buds.
• Face with basic features, eyes, ears is formed
• Heart beat starts
• It is known as embroyo

12 weeks
• 3-4 inches in size and 1 ounce in weight
• Hands, feet, toes and fingers start movement
• Sex becomes differentiated
• Fingerprints are formed
• Urine production starts.
• It is called “foetus”

16 weeks
• 5 1\2 to 6 inches in size, weight is 3 ounces
• Downy hair or lanuga are formed
• Coordinated movements starts
• Heat beats and is also detectable
• Skin is thin and transparent
20 week

• 12 inches in size and 1 pound in weight
• Heart beat can also be detected using stethoscope
• If aborted cannot survive

24 week
• 14 inches in size and 1-1 1\2 pound in weight
• Eyes open up
• Grip gets stronger
• Protective skin covering is formed

28 week
• 16 inches in size and 3 pounds in weight
• Baby is very active at this stage
• Rudimentary breathing starts
• If aborted at the stage can still survive

32 week
• 18 inches in size and 4-5 pound in weight
• Sleep and wakefulness pattern develops
• Meconium production starts
• Starts to assume birth position
• If aborted cannot survive

36 week
• 20 inches in size, 6 pounds in weight
• Baby is lazy
• Protective skin gets thicker
• Baby takes immunity from mother

conclusion: development is a continous process from simplicity to complexity. after the conception i.e fusion of male and female gametes, a zygote divides and multiplies and undergoes three important stages i.e germinal, embryonic and fetal before being delivered.