PSYB32H3 Chapter Notes - Chapter 3: Amniotic Sac, Umbilical Cord, Teratology
Parity is wheter a woman has had a child before. Stages of prenatal development conception during a woman"s ovulation the zygote. It implants on the wall of the uterus. Lasts from the beginning of the third week of gestation until the end of the eighth week. The amniotic sac, membrane around the organisms forms, containing amniotic fluid in which the embryo floats, and the wall tendrils increase in size forming placenta. The embryo is joined to the placenta by the umbilical cord where there is a tramittance of oxygen and nutrients to the infant, and carbon dioxide is removed. 3 layers: ectoderm (hair, nails, skin teeth and nervous system), mesoderm (muscle skeleton circulatory system and excretory system) and endoderm (gastrointestinal tract, trachea bronchia, glands and vital organs) Cephalocaudal: the development proceeds form the head downward to the trunk and legs. Proximal-distal:growth occurs first in central areas, as internal organs then in more distant areas.