Page 70 - Science Course 2 (Book 1)

Mo3-L1b: How do Humans Grow and Develop?

Human Development
Mo3-L1b How Do Humans Grow and Develop?

KEY CONCEPTS:
1. How do humans change during adulthood? During the first two years of life,
called infancy, the muscular and
Let’s Begin nervous systems develop and an
infant begins walking.

Human Development During childhood, which is from about 2 years to

During human development, the zygote develops about 12 years of age, bones in the skeletal system
into an embryo, which is a ball-shaped structure that grow longer and stronger, and the lymphatic system
attaches inside the uterus. matures.

The embryo develops into a fetus, the last stage of
birth.

During the developmental period, called pregnancy, the
organ systems of the fetus will develop and the fetus
will get larger.

During adolescence, growth of the skeletal and
muscular systems continues, organs get larger, and
8-cell stage
4-cell stage the male and female reproductive systems mature.
16-cell stage
2-cell stage
Blastocyst

Fertilized egg

Foetus
(5 weeks)

Foetus
(10 weeks)
Foetus Foetus
(40 weeks) (20 weeks)
Pregnancy

14 weeks Growth and
development continue.
The fetus is about 6 cm long.

8 weeks The embryo is about 2.5cm 16 weeks The fetus is about 15 cm
long. The heart is fully formed and long and about 140g. The fetus can
beating, bones are make a fist and has a range of facial
beginning to harden, and nearly expressions.
all muscles have appeared.

5 weeks The embryo is about 7mm 22 weeks The fetus is about 27 cm
long. The heart and other organs long and about 430g. Footprints
have started to develop. The arms and fingerprints and forming.
and legs are beginning to bud.
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