PSYB32H3 Chapter Notes - Chapter 3: Amniotic Sac, Umbilical Cord, Semipermeable Membrane
Document Summary
Occurs in 3 stages: 1. zygote 2. embryo 3. fetus. During first 2 weeks of life implants itself into the wall of the uterus. Begins when zygote is firmly plants in uterus (3rd week to 8th) By the end, has face, genitalia, fingers and toes. 3 crucial structures develop: amniotic sac, placenta, umbilical cord. Amniotic sac: membrane around organism, contains the amniotic fluid that acts like a shock absorber. Umbilical cord: carry blood back and forth between infant and the placenta. *during the embryonic period, the baby has 3 layers ectoderm: hair, nails, teeth, skin and nervous systems. Mesoderm: muscles, skeleton, circulatory system, excretory system endoderm, gastrointestinal tract, trachea, bronchia, glands and vital organs. 4th-5th week: neural folds begins to close if they do not, child will have spina bifida (portruding spinal column) Prenatal development is guided by 2 principles cephalocaudal: development moves from head down to legs.
