Developmental Psych: 3-Prenatal Development

Amnion

Part of the period of the Zygote. A membrane formed by the trophoblast that encloses the developing organism in amniotic fluid, which helps keep the temp of the prenatal world constant and provides a cushion against any jolts caused by the woman's movement.

Chorion

Part of the period of the Zygote. A protective membrane formed by the trophoblaSt at the end of the second week that surrounds the amnion. From this, tiny fingerlike villi, or blood vessels, emerge.

Placenta

Part of the period of the Zygote. Develops as villi burrow into the uterine wall. By bringing the mother's and father's embryo's blood close together, this part permits food and oxygen to reach the developing organism and waste products to be carried way.

Umbilical Cord

Part of the period of the Zygote. Connected to the placenta. First appears as a primitive body stalk and, during the course of pregnancy, grows to a length of 1-3 feet. This part contains one are vein that delivers blood loaded with nutrients and two arteries.

Embryo

This period lasts from implantation through the 8th week of pregnancy. During these brief 6 weeks, the most rapid prenatal changes take place, as the groundwork is laid for all body structures and internal organs.

Fetus

This period is from the 9th week to the end of pregnancy and is the longest prenatal period. The organism increases rapidly in size, especially from the 9th to 12th week.

Vernix

A white, cheesecake substance that covers the skin, protecting it from chapping during the long months spent in the amniotic fluid.

Lanugo

White, downy hair that covers the entire body, helping the vernix stick to the skin.

Age of Viability

Occurs between 22 and 26 weeks. The point at which the baby can first survive.

Teratogen

Any environmental agent that causes damage during the prenatal period. Rarely have an effect in the period of the zygote. The embryonic period is the time damage is most likely to happen.

Neural Tube

This is one of the first things that forms during the period of the embryo. It will eventually become the spinal cord.