Human Life Stages Unit 8 - Lesson 2

Pre - Fertilization Egg cells are produced in the ovaries The egg then moves to the oviduct for fertilization.

Fertilization Fertilization is the uniting of a sperm and an egg, which begins the entire process of growth and development. Once again, this occurs in the oviduct.

Fertilization When the sperm and egg cells come together, they create a fertilized cell called a zygote. Once the fertilized egg (zygote) moves to the uterus, it attaches to the uterine wall to develop until mature. Zygote

Fertilization Multiple births result from multiple egg releases (fraternal twins) or division of zygote (identical twins).

Identical vs Fraternal Twins Identical Twins Fraternal Twins

Identical vs Fraternal Twins Identical Twins Fraternal Twins

Video - NGC Conjoined Twins Conjoined twins will form when the zygote for identical twins fails to separate. Video - NGC

Pregnancy The period of development before birth is called pregnancy.

Pregnancy The umbilical cord connects the embryo to the placenta which provides nourishment from the mother and removes wastes from the embryo.

Pregnancy The amniotic sac cushions the embryo and stores nutrients and wastes.

Pregnancy embryo fetus The embryo is called a fetus after two months of development. embryo fetus

Pregnancy

Birthing Process Birthing Video Muscular contractions of the uterus push the baby out through the vagina. The umbilical cord is cut after the baby’s birth, and the scar that forms is called the navel (belly button). Babies who cannot be delivered through the birth canal are delivered by caesarian section (C-section). Birthing Video

Stages After Birth Infancy – about the first 18 months of life. Newborns experience fetal stress as they adapt to life outside the uterus. First four weeks are known as the neonatal period. During this period, the infant’s body begins to function normally. Infants are dependent on humans for their survival. Infants quickly increase physical coordination, mental development, and size.

Stages After Birth Childhood – from 18 months to puberty (~12 years old) when physical and mental development continues.

Stages After Birth Adolescence – begins with puberty (reproductive maturity) and ends about age 16-18; hormones produce secondary sex characteristics.

Stages After Birth Adulthood – from approximately age 18 and continues through old age. Muscles and skeleton cease growing. In middle adulthood (30-60 years) body begins to slowly decline. In older adulthood (after age 60) physical body systems decline; average life span is 75 years.