NSG 3111 Lecture Notes - Lecture 2: Protozoa, Endocrine Gland, Pulmonary Artery
Document Summary
Intrauterine development is divided into 3 stages: ovum/pre-embryonic, embryo, and fetus. Cellular replication, blastocyst formation, initial development of the embryonic membranes, and establishment of the primary germ layers. Lasts from day 15 until ~ 8 weeks after conception (when the embryo measures approx. Most critical time in the development of the organ systems and the main external features. Developing areas with rapid cell division are the most vulnerable to malformation caused by environmental teratogens. At the end of the 8th week; all organ systems and external structures are present and the embryo is unmistakably human. Changes during the fetal period are not as dramatic because refinement of structure and function is taking place. The fetus is less vulnerable to teratogens, except for those that affect cns functioning. An agent or factor that causes malformation of an embryo. Refers to the capability of the fetus to survive outsides the uterus. With modern technology, viability is not possible at 20 weeks after.