NATS 1675 Lecture Notes - Lecture 19: Fetal Circulation, Placenta, Endometrium
7 Feb 2013
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Main developments: continued differentiation and growth of tissues and organs. Growth influenced by maternal hormones and later, by fetal hormones: changes in structural form don"t occur anymore. Timeline of major events: end of 8 weeks (months 1-2) Heart beats since 4th week, pumps blood. Head is nearly 50% of body mass: end of 16 weeks (months 3-4) Distinguish between male and female (3rd month) Sry gene on y-chromosome starts development of testes. 6 inches, 6 ounces: end of 28 weeks (months 5-7) 12 inches, 3 pounds: end of 36 weeks (months 8-9) Massive weight gain (~1 pound each week) Fetal circulation through the placenta: functions of the placenta. Source of pregnancy hormones, progesterone and estrogen. Exchanges gases, nutrients, wastes between mother and fetus. Fetus" side: amniotic fluid and amniochoironic membrane. Exchange occurs in: choiron: blood vessels of mother and fetus mix. Uterine veins (carry o-poor blood to mother"s heart) Spiral arteries (bring o-rich blood to intervillus space, near fetus)
