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COURTESY OF ATIKA SCHOOL
ROLE OF PLACENTA
The placenta facilitates the transfer of nutrients from maternal blood to foetus.
Placenta facilitates the removal of nitrogenous wastes from the foetus' blood to maternal blood.
Oxygen from the maternal blood diffuses into the foetal blood while carbon (IV) oxide from foetal blood diffuse into maternal blood.
Production of hormones
Placenta produces progesterone and oestrogen.
The period between conception and birth is called gestation.
In humans gestation takes nine months (40 weeks).
The embryo differentiates into tissues and organs during this period.
Week 1 to 3:
Zygote divides to form blastocyst.
Implantation takes place.
The three germ layers form endoderm, mesoderm and ectoderm.
Nervous system starts to form.
Week 4 to 7:
Development of circulating and digestive systems.
Further development of nervous system, formation of sensory organs,
All major internal organs are developed.
At week 5, heartbeat starts.
Week 8 to 24:
All organs well developed including sex organs.
Hair, finger and toe nails grow.
Foetus move and eyelids open.
Week 25- 30:
The fully developed foetus responds to touch and noises and moves vigorously.
The head turns and faces downwards ready for birth.
Foetus increases in size.