Human Development & Birth

1. Human Development & Birth Chapter 18 Learning Targets Explain the process of fertilization and the conversion of egg into a zygote. Name & give the function of the 4 extra embryonic membranes. Describe the structures & functions of the placenta & umbilical cord. Describe the events that occur during pre-embryonic and embryonic development. Describe the events that occur during fetal development. Describe the 3 stages of birth. Describe the anatomy of the breast & the suckling reflex.

2. Explain the process of fertilization and the conversion of egg into a zygote. LT#1 • Upper third of fallopian tube • One sperm penetrates the egg = NO VACANCY! • Sperm nucleus fuses with egg nucleus = fertilization is complete = zygote • Zygotes begins to divide as it migrates to ward the uterus • Embeds in uterine lining (endometrium) = pregnant

3. Name & give the function of the 4 extra embryonic membranes. LT#2 • Amnion • Chorion • Yolk sac • Allantois See page 366

4. Amnion Allantois Yolk sac

5. Name & give the function of the 4 extra embryonic membranes. LT#2 • Amnion - provides an inner fluid environment • Chorion – the outer membrane that becomes part of the placenta = where fetal blood XΔs molecules with maternal blood • Yolk sac - nutrient material, first site of red blood cell (rbc) formation & becomes part of umbilical cord • Allantois - contributes to the circulatory system – its vessels become umbilical b.v. that transport fetal blood to & from placenta (pg 243)

6. Describe the structures & functions of the placenta & umbilical cord. LT#3 • 2 portions: • (1) fetal = chorionic tissue • (2) maternal = uterine tissue (pg 367) chorionic villi Cover the entire surface of chorion until 8th week & are surrounded by maternal blood & XΔ of materials takes place ax placental membrane BUT maternal blood does not mix with fetal blood Diffusion of O2, glucose, aa from maternal  fetal / CO2, wastes fetal  maternal

7. Describe the structures & functions of the placenta & umbilical cord. LT#3 • Umbilical cord transports fetal blood to & from placenta • Contains fetal arteries & vein to transport waste out & nutrients in • HCG = human chorionic gonadotropic hormone is produced by chorion & then placenta prevents corpus luteum from dying = no menstruation • Placental estrogen & progesterone take over for corpus luteum later on to maintain pregnancy

8. Describe the events during pre-embryonic& embryonic development. LT#4 • First week • Zygote divides repeatedly post fertilization to become morula = compact ball of cells • Morula becomes hollow blastocyst with an inner cell mass surrounded by an outer layer = trophoblast (future chorion)

9. Describe the events during pre-embryonic & embryonic development. LT#4 • 2 week – 8th week • Implantation / tissues present • Nervous system begins / placenta well formed • Limb buds / beating heart / tail • Big head / curved / nose, eyes, ears noticeable • Fingers & toes / cartilaginous skeleton • Bone replacing cartilage • Facial features refined / 1 ½ inches long

10. http://embryology.med.unsw.edu.au/Medicine/FlectureEmbryo.htmhttp://embryology.med.unsw.edu.au/Medicine/FlectureEmbryo.htm • http://www.youtube.com/watch?v=UgT5rUQ9EmQ • http://www.youtube.com/watch?v=aOY16GlqrPw&NR=1

11. Describe the events that occur during fetal development. LT#5 • 3rd to 9th month • Gender distinguishable / fingernails • Skeleton visible / hair appears • White protective coating / heartbeat audible / 6 inches & 6 ounces • Body covered with fine hair / red, wrinkled skin • Testes descend / eyes open / 12 inches & 3 lbs • Body hair disappears / subcutaneous fat deposited • Birth imminent / 21 inches

12. Describe the 3 stages of birth. LT#6 • Birth = parturition • Cervix dilates • Baby is born • Delivery of placenta

13. Cervix dilates – stage 1 • Contractions cause cervical canal to disappear = effacement • Water breaks • Baby’s head acts as a wedge to further assist dilation to 10 cm (see board!)

14. Baby is born – Stage 2 • Uterine contractions every 1 – 2 minutes lasting about 1 minute each • Desire to push • Baby’s head turns so back of head is uppermost • Episiotomy to expand vaginal opening • Once head is delivered baby turns it to the side allowing delivery of the shoulders one at a time • When breathing normally cord is cut

15. Delivery of placenta – Stage 3 • Afterbirth • 15 minutes or so after baby • Uterine muscles contract, shrink uterus and dislodge placenta • Once placental membranes are delivered birth or parturition is complete

16. Describe the anatomy of the breast & the suckling reflex. LT#7 • Breasts contain 15 – 25 lobules each with its own milk duct • Ducts begin at nipple and divide into many other ducts that end in blind sacs called alveoli • Ducts enlarge during pregnancy, increasein # & size • Maternal hormones affect fetus and baby can sometimes produce milk when newborn • No lactation during pregnancy – hormone prolactin is needed • Produced by pituitary after delivery • Colostrum first – milk after 5 days

17. Suckling reflex • Continued lactation requires suckling child • Suckling stimulates nerve endings in areola sending impulses to brain (hypothalamus) which directs the pituitary to produce oxytocin • When oxytocin arrives at the breast it stimulates the lobules to contract & milk flows into ducts = “let down” & easily drawn out by child • More suckling  more oxytocin  more milk • Other oxytocin benefits = uterine shrinkage & bonding