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Fertilization Occurs in the Ampulla of the Ovidcut/Fallopian Tube

Implantation Happens on ~ Day 6, the trophoblast penetrates the endometrium

Teratogen Exposure Developing fetuses are most vulnerable to teratogenic effects starting at week 3 and continuing until week 8

Embryonic Period Starting week 4, a lot of major organ development begins. Neural tube closes, heart begins beating, limbs start to form

Fetal Period Starting week 8, fetal period begins. The developing fetus begins to move

Sexual Recognition Starting week 10, sexual characteristics of the developing fetus are recognizable via ultrasound

Phase 0 of Parturition: Uterine muscle tranquility, cervical rigidity. Myometrial cell hyperplasia, hypertrophy, unresponsiveness, limited availability of uterotonins, limited contractile signals. Progesterone activity

Phase 1 of Parturition: Gradual increase in uterine responsiveness, functional withdrawl of progesterone, increases in cortisol,

Phase 2 of Parturition: Labor onset, increased uterotonin production, and gap junction formation. Spontaneous uterus contractions, progressive cervical dilations, expulsion of fetus

Phase 3 of Parturition: Placental expulsion, uterine involution, milk letdown caused by Oxcytocin. Restoration of fertility based on duration of breastfeeding. Longer breastfeeding = slower restoration of fertility

Embryonic Stage (3-7 weeks post conception) Begins around week 3, Lung bud arises from foregut and the trachea and esophagus separate

Pseudoglandular stage (5-17 weeks) Tracheo-bronchial tree forms, airway branching. Lymphatics, cilia, goblet cell differntiation

Canalicular stage (17-28 weeks) Alveolar type I and II cells differentiate, Lamellar bodies form (early surfactant)

Saccular stage (29-35 weeks) Distal air spaces branch and grow, Surfactant formation escalates, Fetal lung fluid and fetal breathing

Alveolar stage (36 weeks – ~8 years) Alveolar septal walls thin out b. Alveolar surface area increases