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Pregnancy & Development

Pregnancy & Development. P & A. IX. Pregnancy. A. Def: condition resulting in union of sperm and egg and a fetus developing in the uterus B. How occur? 1. semen containing sperm is deposited in vagina 2. sperm travels up through uterus & uterine tubes

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Pregnancy & Development

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  1. Pregnancy & Development P & A

  2. IX. Pregnancy • A. Def: condition resulting in union of sperm and egg and a fetus developing in the uterus • B. How occur? • 1. semen containing sperm is deposited in vagina • 2. sperm travels up through uterus & uterine tubes • A. able to move b/c of tails and sugary energy • B. estrogen is high in first part of menstrual cycle • - causes uterus and cervix to create a watery secretion that aids in sperm transport • C. second part of cycle progesterone is high • - secretion prevents good sperm travel

  3. 3. when sperm penetrates egg membrane, nuclei of the two combine = 46 chromosomes • A. first cell of life = ZYGOTE • B. after 32 hrs = zygote starts dividing = mitosis • C. zygote now called EMBRYO • D. after 3 days, embryo arrives to uterus • E. after 1 week – embryo attached in uterine wall • Endometrium • F. after 8 weeks – now called FETUS • Body is recognizable as human • G. outer embryo/fetus cells and endometrium form the placenta • Def: bloody sac that exchanges nutrients, gases, and wastes between mother and baby • Also acts as a barrier to some toxins

  4. c. Hormonal changes in pregnancy • 1. human chorionic gonadotropin (HCG) • A. def: hormone that prevents normal decline in estrogen and progesterone that causes uterine lining to shed away (menstruation) • Hormone that a pregnancy test detects • B. if this hormone fails or there is not enough = miscarriage will result • 2. placental estrogen • A. def: hormone secreted by placenta that maintains thick uterine wall • 1. also causes relaxation of pelvic joints – helps in birthing process

  5. 3. placental lactogen • A. hormone secreted by the placenta that allows for breast development and milk production

  6. X. Embryonic dev (2nd-8th week) • A. germ layers • 1. def: layers of cells in an embryo that arise to form body structures • A. ectoderm: nervous system, hair, nails, skin, mouth, anal canal • B. mesoderm: muscle, bone, blood, lymph, reproductive organs • C. endoderm: digestive, respiratory, and urinary tracts • B. pre-natal nourishment • 1. amnion • A. membrane around embryo • B. filled with fluid = amniotic fluid • Contains same cells as baby = samples used for genetic testing

  7. C. umbilical cord forms • 1. provides a pathway for nutrients from placenta to embryo • C. By the end of the 8th week • Baby length = 30 mm • Baby weight = less than 5 g. • ** THESE FIRST FEW MONTHS ARE VERY CRITICAL IN BABIES’ DEVELOPMENT • - mother should immediately see Dr. when suspect pregnant • - nutrition is very important!

  8. xi. Fetal development – 9th week - birth • ** Lunar month = 28 days • A. 3rd lunar month • 1. body length grows greatly • 2. head growth slows • 3. ossification centers develop • 4. by end of 12th week, reproductive organs visible • B. 4th lunar month • 1. body grows to 13-17 cm • 2. skeleton ossifies

  9. C. 5th lunar month • 1. growth supresses • 2. skeletal muscles active = mother feels movement • 3. hair develops • D. 6th lunar month • 1. large weight gain • 2. eyebrows and eyelashes appear • E. 7th lunar month • 1. fat deposited = smooths out skin • 2. eyelids open • 3. approx 37 cm in length

  10. F. 8th lunar month • 1. testes of male descend • * sometimes this doesn’t happen and surgery is needed • G. 9th lunar month • 1. body chubby b/c of fat deposits • 2. skin pink • H. 10th lunar month • 1. full term • 2. skin sebum coated • 3. scalp has hair • 4. skull bones ossified • 5. nails developed • 6. head positioned to cervix

  11. XII. Fetal circulation • A. blood in the pulmonary artery bypasses the lungs by entering DUCTUS ARTERIOSUS • - which brings blood back to aorta

  12. xiii. labor • A. uterine & vaginal stretching in late pregnancy • 1. initiates hypothalamus to signal posterior pituitary gland • 2. PPG releases oxytocin • - stimulates uterine contractions • 3. rhythmic contractions send uterine contents to cervix • - signals stronger contractions = POSITIVE FEEDBACK • 4. fetus forced outside • 5. 10-15 minutes after birth, placenta separates from uterine wall & is delivered

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