explain in detail three main strimesters in human pregnancy add a note on placenta
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Answer: Human pregnancy is of 9 months, which is divided into 3 trimesters.
1st trimester
Answer: Human pregnancy is of 9 months, which is divided into 3 trimesters.
1st trimester
- During the first three months, as soon as the fertilization occurs, the zygote is formed followed by embryo formation.
- When the embryo is implanted successfully in the maternal uterine wall, gastrulation starts where three germ layers are formed that is ectoderm, mesoderm and endoderm.
- After one month of pregnancy in human beings, heart and certain facial features are formed in the embryo. Foetus develops organs like limbs, feet and digits by the end of the second month of pregnancy.
- By the end of 1st trimester, major vital organs like kidneys, liver, intestine, brain, external genital organs are formed and the hardening of bone also starts.
- With the beginning of 2nd trimester, the heart starts pumping blood, and the foetus starts taking in amniotic fluid for the development of air sacs within the lungs. By the end of 2nd trimester, movement of limbs occurs, and the formation of eyelids and eyelashes occur. The body gets covered with fine hair.
- During the last three months, the brain develops effectively by developing a network of billions of neurons, skin starts covering with fat and overall development of the body occurs
- At the end of 9 months, the foetus develops completely and ready for delivery.