Page 72 - EM BIOLOGY NOTES 10TH CLASS PSR DIGITAL BOOKS

DRAWING DIAGRAMS - PARTS - PROCEDURE

HUMAN EMBRYO Human embryo development
1. Due to the fertilization zygote forms in follopian tube.
2. Zygote travells from fallopian tube to uterus.
3. At the time of travelling zygote undergoes division and forms as Blastocoel.
4. Further development of the embryo occurs in the uterus.
5. From the third month of pregnancy, the embryo is called foetus.
6. The growing embryo forms two membranes - chorion, Amnion, Allantois and yock sac.
7. Amnion forms grows as a sac like structure around the embryo.
8. The space between the Amnion and embryo is filled with a fluid called amniotic
fluid. It gives protection to the embryo against mechanical shocks.
9. Chorion establishes connection with the walls of uterus for supply of nutrients to
the embryo and for removal of wastes from the embryo is called Placenta.
10. Placenta is a tissue formed by the cells from the embryo and the mother. It is
formed at around 12 weeks of pregnancy.
11. Embryo receives all the required nutrients and oxygen for its metabolism from
the mother through umbilical cord.
12. Umbilical cord is a tube like structure, which originates from the digestive canal of the embryo.

SEX DETERMINATION IN HUMAN BEINGS Sex determination in human beings
1. Each human cell contains 23 pairs of chromosomes.
2. Out of 23 pairs 22 pairs are autosomes, 1 pair is allosomes. How to draw
pl. scan QR
3. Allosomes are two types one is ‘X’ and other is ‘Y’.
4. These two chromosomes determine the sex of an individual.
5. Females have two ‘X’ chromosomes in their cells, while males have one ‘X’ and
one ‘Y’. In females = Allosmes - ‘XX’, in males = Allosomes - ‘XY’.
6. All the gamates produced by a woman have one ‘X’ chromosome.
7. But the gamates produced by a man are two types. One with ‘X’ chromosome and the other with ‘Y’.
8. If a sperm which is having ‘Y’ chromosome is fertilizes the ovum, zygote contains
‘XY’ chromosomes. Hence the zygote will be develops as a boy.
9. If a sperm which is having ‘X’ chromosome is fertilizes the ovum, zygote having ‘XY’
chromosome. Hence the zygote will be developing as a girl.
10. So, the sex determination of the baby depends on the sex chromosome carried by the sperm.
11. So, male is the responsible for sex determination of the baby.
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