PSYB20H3 Chapter Notes - Chapter 3: Umbilical Cord, Embryonic Disc, Amniotic Sac
Document Summary
The prenatal period of development, between conception and birth, is called gestation. The normal range of gestation is between 37 and 41 weeks. Prenatal development takes place in 3 stages germinal, embryonic and fetal: during these stages, the fertilized ovum zygote grows into an embryo and then a fetus. 2 fundamental principles: growth and motor development. The cephalocaudal principle, fro(cid:373) lati(cid:374), (cid:373)ea(cid:374)i(cid:374)g (cid:862)head to tail,(cid:863) dictates that develop(cid:373)e(cid:374)t proceeds from the head to the lower part of the trunk. An embryo"s head, brain, and eyes develop earliest and are disproportionately large until the other parts catch up. At two months of gestation, the embryo"s head is half the length of the body. By the time of birth, the head is only one-fourth the length of the body but is still disproportionately large. According to the proximodistal principle , fro(cid:373) lati(cid:374), (cid:862)(cid:374)ear to far,(cid:863) development proceeds from parts near the centre of the body to outer ones.
