Gametes, Fertilization And Implantation

Front 1

What happens to the oocytes when a woman hits puberty?

Back 1

The oocyte which was arrested at prophase 1 will now complete meiosis 1 around ovulation and then arrest at metaphase of meiosis2.

Front 2

What happens to the secondary oocyte after fertilization?

Back 2

fertilization will trigger the completion of meiosis 2 which results in a mature oocyte

Front 3

Factors that contribute to non-disjunction

Back 3

1. error in spindle fiber attachment

2. defect in synapsis and maintenance of cross-overs

3. defect in cohesion of sister chromatids

4. oocytes lack effective spindle tensional checkpoint

Front 4

nondisjunction

Back 4

anything that causes incorrect sorting of chromosomes during meiosis or mitosis

Front 5

What's the difference between getting nondisjunction in meiosis 1 vs meiosis 2

Back 5

nondisjunction in meiosis 1 will results in none of the gametes having the correct number of chromosomes. in meiosis 2 nondisjunction will cause 2 cells to be aneuploidy while the other 2 gametes will be normal

Front 6

4 ways to diagnose aneuploidy before the birth of the baby

Back 6

1. Aminocentesis (14-16weeks)

2. Chorionic villus - placental sampling (10-12 weeks)

3. Maternal blood testing for fetal cells (early as 6 weeks) -limited info

4. Pre-implantation genetic screening in IVF lab

Front 7

twin formed from splitting of zygote

Back 7

monozygotic, dichorionic, diamniotic

Front 8

twins formed from complete splitting of inner cell mass

Back 8

monozygotic, monochorionic, diamniotic

Front 9

twins formed from two eggs ovulated and fertilized separately

Back 9

dizygotic/fraternal, dichorionic, diamniotic

Front 10

twins formed from incomplete splitting of inner cell mass

Back 10

monozygotic, monochorionic, monoamniotic

Front 11

twins formed from late separation

Back 11

conjoined twins, monozygotic, monoamniotic

Front 12

What's a possible hazard of monochorionic twins?

Back 12

growth disparities due to unequal placental circulations

Front 13

What's a possible hazard of monoamniotic

Back 13

tangled/knotted umbilical cord

Front 14

differentiation of spermatid to sperm

Back 14

mitochondria --flagellum

golgi -- acrosome

condensation of nucleus

excess cytoplasm discarded

Front 15

through what mechanism do MOST autosomal aneuploidies rise from

Back 15

nondisjunction in female meiosis 1

Front 16

What problem arises for sperm with age?

Back 16

as men age they have a higher chance of a mutation in their spermatogonia which would lead to autosomal dominant de novo mutations

Front 17

3 functions of zona pellucida

Back 17

1. sperm binding site (this triggers acrosome reaction)

2. block to polyspermy via cortical reaction

3. prevent premature/ectopic implantation

Front 18

Sperm capacitation

Back 18

sperm is normally coated with cholesterol/glycoproteins until it sheds that coat by vaginal secretions. Ca++ influx leads to hyper-activation of sperm motility

Front 19

Main events of fusing of sperm and egg

Back 19

-cortical reaction

-egg completes meiosis II

-egg nucleus decondenses (pronucleus)

-fusion of egg and sperm pronuclei --> zygote

Front 20

Cleavage division steps

Back 20

blastomeres > morula >(compaction) blastocyst > inner cell mass

Front 21

What happens when you get implantation close to the cervix?

Back 21

placenta previa

Front 22

when the trophoblast comes into contact with the endometrium it differentiates into these two layers

Back 22

invasive syncytiotrophoblast

internal cytotrophoblast

Front 23

What are the roles of syncytiotrophoblast?

Back 23

1. Secretes enzyme to degrade uterine wall to pull in the blastocyst

2. secretes hCG (detected in urine/blood for pregnancy test)

Front 24

How does the endometrium respond to trophoblast invasion? (3 things)

Back 24

1. Decidual reaction of stromal cells -- they accumulate glycogen and lipids and will be engulfed by the trophoblast to nourish the embryo

2. Angiogenesis

3. Gland secretion

(all used to nourish embryo)

Front 25

What are lacunar spaces?

Back 25

internal membrane channels in syncytiotrophoblast which allows mixing of maternal blood and secretion (uteroplacental circulation)

Front 26

What are the problems with ectopic pregnancy

Back 26

most ectopic pregnancies occur in the fallopian tube so there isn't enough space for the fetus to develop and the tissues of the fallopian tube are unable to form stable vessels

Front 27

The epiblast gives rise to the germ layers while the hypoblast contributes to

Back 27

yolk sac lining

Front 28

How is the amniotic cavity (sac) formed?

Back 28

fluid secretion by aminoblasts

Front 29

What are the three cell types/layer that are part of the chorion?

Back 29

1. syncytiotrophoblast

2. cytotrophoblast

3. extraembryonic mesoderm