1. Pregnancy & Development
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2. 1. Fertilization – Days 0-6
Sperm reaches the egg in the fallopian tubes, forming a zygote
The zygote divides until it becomes a ball of cells called a blastocyst.
The blastocyst implants or attaches to the lining of the uterus.
Now the blastocyst is called an embryo.

3. 2. First Trimester – Weeks 1-13
Cells are rapidly dividing and forming the specialized tissues that make up the body, at this point called an embryo.
At five weeks, the heart begins to beat
At nine weeks, the embryo has developed enough to become a fetus.

4. 3. Second Trimester – Weeks 14-26
Fetus continues to develop and becomes more active
The mother can begin to feel the fetus moving
Fingers and toes are fully formed

5. 4. Third Trimester – Weeks 27-40
Fetus grows to its largest size
Lungs fully develop so that it can breathe on its own once it leaves the mother’s body

6. 5. Birth Labor begins with the uterus starts contracting
The mother’s cervix dilates or gets larger to allow the baby to pass from the uterus through the birth canal
The muscles of the uterus push the baby out of the mother’s body, head- first.
The mother must also expel the placenta, the organ that allows mother and embryo to exchange oxygen, nutrients, and waste

7. 6. Human Life Stages
Infancy lasts from birth to age 2. This is a time of dramatic growth.
Childhood lasts from age 2 to age 12. This is a time of slower physical growth, but maturing of the nervous system.
Adolescence begins with sexual maturity. For girls, this is when they begin their menstrual cycle. For boys, this is when sperm starts to appear in the semen.
Adulthood is when humans are fully developed and may raise families of their own.