Development Embryo to Fetus to Birth 1 3

Development Embryo to Fetus to Birth 1 -3 Trimesters

Neurula Day 28 2 -3. 5 mm

Amniotic Sac • Originally forms around the embryo • Eventually fills with liquid provided by the mother’s cells • Later, formed by the fetal kidneys • Circulates when the baby drinks the liquid and excretes it out

Amniotic Sac • Some babies are born inside the amniotic sac • 1 in 80, 000 births • http: //www. cnn. com/2015/02/2 5/health/rare-en -caul-birthamniontic-sac/

Umbilical cord Placenta • Placenta: holds baby to the mother • Diffusion of food, oxygen, carbon dioxide and waste takes place

• Umbilical cord contains an artery and a vein • One carries things to the baby • One carries things away from the baby

4 weeks • Brain is formed • Heart is beating • Eye, legs, arms begin • 1/6 inch

6 weeks • ½ inch • Circulation begins • Toes and fingers forming

1. 2 inches 8 Weeks § Eyes, nose, lips, tongue, ears and teeth are forming § Gonad formation begins § Functioning heart § Now considered FETUS

12 Weeks 2. 5 – 3 inches and. 5 – 1 oz. • Sex of the baby can be determined • Nails and earlobes develop • Eyes almost fully developed • All parts present, now major GROWTH and DEVELOPMENT

2 nd Trimester Week 13 to Week 27 • Placenta fully developed • Fetus can hear mother • Vernix forms – creamy white substance that protects thin skin

2 nd Trimester • Skin is reddish and forms lanugo (downy hair) • Reflexes: swallow, suckling, jumping

end of 2 nd trimester: 15 inches long 2. 5 pounds • Sleep – wakefulness cycles • Fat forms • lungs are beginning to exhale amniotic fluid (practice for breathing) • circulatory system working

3 rd Trimester Week 28 to Week 40 • Fetus has sight and hearing • Soft skeleton • Laguno disappears – skin begins pigmentation • Circulatory and Respiratory systems mature

• Mother’s antibodies pass to fetus • Digestive organs expel wastes- meconium • Baby moves downward towards birth canal

Parturition (Birth) • Expel fetus from uterus = LABOR • Last few weeks of pregnancy, estrogen levels peak: – myometrium forms oxytocin receptors – Interupts progesterone, allows small uterine contractions (false labor, Braxton Hicks) • Oxytocin production causes placenta to release prostaglandins = more powerful contractions

Positive Feedback Loop • Hypothalamus activated by increasing pressure levels on the cervix • Activates pituitary to release more OXYTOCIN…

Three Stages of Labor: DIALATION • True contractions dilates cervix 1 to 10 cm • Contractions – Increase from weak to vigorous – Regular – Upper uterus downwards to birth canal – Soften cervix: effaces – 6 -12 hours

Three Stages of Labor: EXPULSION • Delivery of infant out of vagina • Mother’s response is to push • Infant is facing downwards: vertex, if butt down: breech • Mucus is suctioned before full delivery – baby begins to breathe • Complications (dropping oxygen levels or heart rate in infant) overcome by forceps, vacuum or Cesarean section

Three Stages of Labor: PLACENTAL • Uterine contractions compresses blood vessels • Placenta detaches • Afterbirth = placenta, fetal membranes and umbilical cord • Need to remove all tissues – could cause excess bleeding

Thank your mother… Uterus stretches to occupy most abdominal cavity Estrogen/progesterone surge (morning sickness) Ribs flare (shortness of breath, but vital capacity increases) Lordosis – lumbar curvature (back aches) Relaxin causes pelvic ligaments and pubis to widen/relax (duck walk) • Organ displacement = pressure on esphogus, stomach, and intestines (heartburn, small meals, constipation) • Excess waste from fetus and limited room (frequent urination…uncontrollable) • Blood volume increases up to 40% , blood pressure and pulse rate increases (swelling = edema) • • •