-most the umbilical vein’s blood flows through the ductus venosus directly into the inferior vena cava, bypassing the liver because mom’s liver does most of the work; blood goes straight up into baby’s heart because we want blood to be used for the major organs o Foramen ovale -blood that enters the right atrium passes through the foramen ovale into the left atrium, and pours into the left ventricle, which pumps it into the aorta; allows blood to bypass the lungs b/c gas exchange is unnecessary before birth; only need blood to grow; allows blood to go from right to left across septum o Ductus arteriosus : allows the blood to go out the pulmonary artery to the aorta; PDA (patent ductus arteriosus) murmur sounds like washing machine; whooshing sound Embryonic and fetal development and influencing factors=2 questions A term pregnancy is 280 days; 10 lunar months (28 days) or 40 weeks; 10 calendar months. Pre-embryonic stage = conception to day 14 o characterized by: cell multiplication and differentiation Embryonic stage= day 15 through 8 weeks o All the essential organs are forming: heart, spleen, brain, liver; by the end of 8 weeks everything it needs to be a human organism is there o Characterized by: the heart begins beating between 3 ½ to 4 weeks gestation; we can hear the heart beat by 6 weeks by ultrasound o by 6 weeks the liver is making RBCs; the yoke sac will make RBCs before that o fetal circulation is established at 6 weeks o lip and palate are formed between 7-9 weeks gestation; brain waves present by 6 weeks gestation Fetal Stage = 8 weeks to birth o Every organ system and external structure that will be found in a full-term newborn is present; rest of this stage devoted to refining structures o by 12 weeks the gender is well differentiated (determined at conception); at 16 weeks the sex of the fetus can be determined visually o by the end of the firth trimester (10-11 weeks) eye lids fuse together and will unfuse around 24 weeks gestation o can make a fist by 16 weeks gestation o by 20 weeks lanugo is formed (baby may swallow it) and vernix is on the skin to protect it (begins to drop off) o at 20 weeks, fetal heartbeat can be auscultated by a fetoscope and quickening occurs o by 28 weeks baby looks like an old person (baby weighs 2 lbs.); after 28 weeks, baby puts on weight in the last 12 weeks Influencing factors Quality of Sperm or Ovum-if one of them has a problem; then there’s going to be something wrong with the baby and its development Adequacy of Intrauterine Environment o injurious agents ( teratogens )-any agent (drug, virus, or chemicals) which can cause development of abnormal structures in an embryo; because organs are formed primarily during embryonic
development, the growing organism is considered most vulnerable to hazardous agents during the first months of pregnancy (esp. during first 8 weeks when organ systems are developed) o maternal nutrition (baby’s brain is growing the fastest 20 weeks gestation to 6 mo after delivery;
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