LECTURE 12 and 13

Question 1

what steps follow fertilization?

Answer 1

1. oocyte finishes meiosis 2 and forms a zygote. cells divide to become a morula, then a blastocyst

Question 2

where is the blastocyst located?

Answer 2

rests unattached in the uterus for 2-3 days, grows a bit deriving nutrients from uterine gland

Question 3

what happens to the zona pellucida after fertilization?

Answer 3

6 days after fertilization, zona pellucida is broken down by a protease from the uterus

Question 4

when does fertilization occur?

Answer 4

7-10 days after fertilizatioin in the wall of uterine fundus

Question 5

how does the placenta form?

Answer 5

chorion eventually fuses with amnio and yolk sac eventually degenerates

Question 6

how do placents form different for fraternal twins that were implanted separately vs together

Answer 6

if separate, 2 placentas, chorions, and amnions appear. if teogether, single placenta, fused chorions, and 2 amnions are present

Question 7

how do placentas for for monozygotic twins?

Answer 7

pregnancy with identical twins usually occurs when inner cell mass of blastocyst divides and produces 2 embryos with single placenta but 2 amnionic sacs

Question 8

3 parts of fetal circulatory sytem

Answer 8

ductus arterisus: bypasses fetal lungs
foramen ovale: allows mixing of blood between right and left heart chambers
ductus venosus: bypasses liver

Question 9

stages of birth

Answer 9

stage 1 (effacement) : soften and thin out cervix, usually light contractions, 30-60 seconds, 5-20 minutes apart

stage 1 (early dilation): open cervix from 0-7 centimeters. stronger contractions, 60 seconds long every 1-3 minutes. total duration 5-9 hours for first baby, 2 to 5 hours for others

stage 1 transition: continuing to open cervix from 7 to 10 centimeters, extremely strong and erratic contractions, 50-90 minutes long, every one minute (very short duration)

stage 2: expulsion: to expel baby from uterus. less strong than transitional stage. 60 seconds long every 1-3 minutes (30 minutes to 2 hours total)

Question 10

how does effacement and dilation differ in primiparious woman and multiparious women

Answer 10

in primiparous (first timers) effacement occurs before dilation

in multiparous women effacement and dilation occur together

Question 11

two abnormal birth positions

Answer 11

breech and transverse

Question 12

amniocentesis

Answer 12

under guidance of ultrasound, sterile needle is inserted into amniotic sac to draw a small amount of amniotic fluid. fluid contains fetal cells which are cultured and then tests are performed on cultured cells. (15-18th week of pregnancy

Question 13

chornionic villi sampling

Answer 13

10-11 week fetus. catheter inserted into vagina and cervix into uterus placed in contact with chorion (outer layer of placenta) small suction removes small piece of chorion
cells of chorion are used directly for genetic tests

Question 14

layers surrounding baby from inside out

Answer 14

amniochorionic membrane
amniotic fluid
chorion
endometrium
(chorion + endometrium are the placenta)

Question 15

fetal cell sorting

Answer 15

fluorescence/magnetic anti-cd71 to fetal cells

blood tests: alpha feto protein is very high in fetuses with neural tube defects

Question 16

diagonal conjugate

Answer 16

pubic bone to sacral promontory

11.5 min 13.5 avg

Question 17

transverse outlet diameter

Answer 17

ischial spine: 8.5 cm (min) 10 cm avg