8th Grade-Ch. 7 Sec. 3 The Human Life Cycle

Ch. 7 Sec. 3 The Human Life CycleObjectives:1.What are the stages of human development that occur before birth?2.How is the developing embryo protected and nourished?3.What happens during childbirth?4.What changes occur from infancy to adulthood?

zygote embryo fetus

Up to 8 weeks

9 weeks birth

zygote1. moves down fallopian

tube

2. begins 2 divide

3. forms hollow ball

4. attaches to uterus = embryo (from 2 cell stage 8th week)

embryo

fetal developmentMONTHS FETAL DEVELOPMENT

BY 3RD MONTH

•Looks like baby

•Internal organs (brain, etc) developing

4-6 MONTHS •Bones

•Heartbeat

•Movement

7-9 MONTHS •Fetus doubles in length

•Lungs develop

protection & nourishment

amniotic sac

• fluid filled sac that cushions & protects developing baby

placenta• links embryo & mom- receives nutrients &

oxygen - gives off carbon dioxide & wastes

umbilical cord• rope between fetus & placenta

3 stages of birth

1.labor 2.delivery 3.afterbirth

•contractions•cervix gets bigger

baby pushed out uterus vagina

mom’s body

placenta/ membranes

come out

Figure 14 pg. 237-Twins

Fraternal twins are from 22 eggs & 22 sperm.

Unlike identical twins, fraternal twins have their own placenta and amniotic sac, which prevents

them from actually touching each other.

Triplets are born in about 1 out of every 7,000 births.

infancy

infancy

Shape & size change greatly

When born-head makes ¼ body

Dependent on others

childhood

childhood

Starts @ 2 yrs.

Bones & muscles grow

More coordinated

Language develops

adolescence

adolescence

Become adults physically & mentally

puberty-able to reproduce

Girls-ovulate & menstruate

adulthood

adulthood

After age 30-get wrinkles, muscles decrease

Puberty ends

Mental & emotional growth cont.

Become wiser