Unit N - Final anatomy test god bless

Gestation period

The full length of pregnancy, about 9 months (40 weeks) in humans.

Embryonic period

The stage from about week 3 to week 8 when major organs and body systems begin forming.

Fetal period

The stage from week 9 until birth when the fetus grows and matures.

Cleavage

Rapid mitotic divisions of the zygote without growth in size.

Morula

A solid ball of cells formed after several rounds of cleavage.

Blastocyst

A hollow ball of cells with an inner cell mass that will become the embryo; implants in the uterus.

Gastrula

An early developmental stage where the three germ layers form.

Ectoderm

Outer germ layer; forms skin and nervous system.

Mesoderm

Middle germ layer; forms muscles, bones, and circulatory system.

Endoderm

Inner germ layer; forms digestive and respiratory systems.

Organogenesis

The process by which organs form during development.

Amniotic sac

A fluid-filled sac that surrounds and protects the developing embryo/fetus.

Umbilical cord

A cord connecting the fetus to the placenta, allowing nutrient and waste exchange.