BIOL 261 Lecture Notes - Lecture 21: Umbilical Cord, Corpus Luteum, Hemoglobin
Document Summary
23. 2 pregnancy and the prenatal period: pregnancy: the presence of a developing offspring in the uterus. Extends from fertilization through the eighth week of prenatal development placenta forms, the main internal organs develop, and the external body structure appear: period of cleavage: zygote (sperm cell+ secondary oocyte) rapid divisions (mitosis) Chorion amnion (umbilical cord) amniotic fluid embryonic disc (yolk sac: gastrulation and organogenesis, gastrulation: movement of cells within the embryonic disc to form multiple layers (ectoderm, mesoderm, endoderm; primary germ layers, organogenesis: formation of organs from primary germ layers. Extends from birth to the first four weeks. Continual development extending from the end of the first four weeks to one year; infant grows rapidly and may triple its birth weight. Begins at the end of the first year and ends at puberty. Adolescence development between puberty and adulthood when anatomical and physiological changes result in reproductively functional individuals.
