Lecture 2 (gametogensis -> gastrulation/end of wk 3) Flashcards

1
Q

Why is a zygote protected from exposure in the 1st two weeks of development?

A

implantation doesn’t occur until roughly 2 weeks after fertilization (not connected to mother yet)

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2
Q

What timeframe is the fetus most sensitive to exposures?

A

weeks 3-8

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3
Q

Where/as what do germ cells originate?

A

outside of the gonads

primordial germ cells

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4
Q

Where are germ cells formed? Where do they travel?

A

in the epiblast in 2nd wk

travel to the wall o the yolk sac

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5
Q

When do the germ cells arrive at the gonads?

A

by the 5th week of pregnancy

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6
Q

primordial germ cells migrate to where after gastrulation?

A

they migrate to the somatic region of the kidney and then differentiate thank to their somatic cell partners

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7
Q

during what period do oogonia increase in number? what process is this?

then what happens?

A

2nd and 5th month of pregnancy - mitosis

atresia until menopasuce

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8
Q

When do spermatogonia undergo mitotic arrest? When do they resume division?

A

perinatally

at puberty

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9
Q

How long does it take for sperm to mature?

A

64-74 days

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10
Q

What cells hold all spermatogonia?

A

sertoli cells

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11
Q

Which type of spermatogonia undergo meiosis?

A

Type B

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12
Q

Once Type B spermatogonia undergo meiosis I you have ->

A

secondary spermatocytes

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13
Q

Secondary spermatocytes undergo ________ to form ->

A

meiosis II

4 haploid spermatids

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14
Q

spermatids mature and become ->

A

spermatozoans

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15
Q

How long does spermatogenesis take? What is the beginning and end?

A

64 days

spermatogonia -> spermatozoa

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16
Q

Primary oocytes are frozen in ->

A

Meiosis I

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17
Q

How many follicles mature every month in females? When does this begin? How many reach full maturation?

A

15-20

after puberty

only one

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18
Q

When does the oocyte cease Meiosis II? does it begin again?

A

3 hours before ovulation

and yes, if fertilized

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19
Q

What is leftover once the ovum is released from the Graffian follicle?

A

the corpus luteum

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20
Q

What does the corpus luteum do?

A

produces hormones like progesterone to prepare the uterus for implantation

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21
Q

What does the corpus luteum become if fertilization doesn’t occur?

A

the corpus albicans

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22
Q

What forms the acrosome of the sperm?

A

golgi bodies accumulate

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23
Q

What organelle(s) are left in the mature sperm?

A

mitochondria

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24
Q

What damages mitochondria in sperm? How far out can these exposures impact pregnancy?

A

oxidative stressors

30-60 days

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25
Q

What hormone is required for the production of testosterone?

A

LH

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26
Q

Where does fertiization typically occur?

A

ampullary region of the uterus

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27
Q

What happens to the sperms prior to fertilization?

A

capacitation -> sheds glycoproteins

28
Q

What happens once the sperm binds to the zona pellucida?

A

acrosome rxn -> sperm can now make it’s way to egg’s cell membrane

29
Q

What happens after the sperm breaks down the zona pellucida?

A
  1. it binds to cell membrane
  2. cell membrane hardens so no other sperm can bind
  3. membranes fuse together and sperm nucleus enters
  4. pronuclei fuse together
  5. form the diploid zygote
30
Q

What occurs during 0-3wks?

A

early development
cleavage
gastrulation

31
Q

What takes place from 4-8wks?

A

period of embryonic organogenesis

32
Q

What is considered 9-38wks?

A

fetal period

33
Q

How long after fertilization does the 1st cell division occur?

A

30-36 hours

34
Q

Meiosis is completed ___________ after the ovum is released.

A

12-24 hours

35
Q

By day 3 you have the:

A

morula stage

36
Q

By day 4 you have the:

A

blastocyst

37
Q

btwn thew morula and early blastocyst the embryo undergoes:

A

compaction

38
Q

the blastocyst becomes two cell layers, known as _________. when does this happen?

A

inner cell mass
trophoblasts (outside)

days 4.5-5

39
Q

What pole does the ICM form on of the embryo?

A

animal pole

40
Q

What occupies that opposite pole of the ICM?

A

fluid-filled space that -> endodermal layer and yolk sac

41
Q

Where do ectopic pregnancies occur?

A
abdominal cavity 
ampullary region of the tube (80%)
tubal implantation
interstitial implantation
implantation in region of the internal os
42
Q

How do ectopic pregnancies occur?

A
  • due to invasive nature of trophoblasts

- due to abnormal transport or recognition of blastocysts

43
Q

What are some adverse outcomes of ART?

A
embryo effects
spontaneous abortions
multiple births
adverse perinatal outcomes
birth defects
DD
childhood malignancies
longer-term outcomes?
44
Q

the inner cell mass is also known as the:

A

embryoblast

45
Q

What two things are interacting as the 1st week ends?

A

syncytiotrophblasts and the endometrium

46
Q

What days make up wk 2?

A

Days 6-15

47
Q

What’s the other name for the 2nd week of development?

A

The week of 2s

48
Q

During the 2nd wk of development, the trophoblast gives rise to ->

A

cytotrophoblasts

syncytiotrophoblasts

49
Q

During the 2nd wk of development, the embryoblast gives rise to ->

A

hypoblast

epiblast

50
Q

During the 2nd wk of development, the extraembryonic mesoderm ->

A

splits into the somatic (parietal) and splanchic (visceral) layers

51
Q

During the 2nd wk of development, what cavities form?

A

yolk sac

amniotic cavity

52
Q

By what day is the embryo implanted into the endometrium?

A

Day 7.5

53
Q

What is happening in the syncytiotrophoblasts on day 9?

Maternal blood vessels?

A

lacunae are forming

blood vessels are enlarging

54
Q

What is occurring in the syncytiotrophoblasts by day 12?

A

maternal sinusoids are fusing with lacunae

55
Q

What begins forming by Day 13?

A

primary villi surrounded by trophoblastic lacunae filled with maternal blood

56
Q

When do the primitive streak and node begin forming?

A

Day 15

57
Q

In what direction does the primitive streak grow?

A

caudal to cranial

58
Q

What happens as the primitive streak forms?

A

cells invaginate and migrate through the primitive streak

59
Q

What happens to the first wave of cells that migrate thru the primitive streak?
When does this begin?

A

they replace the hypoblast cells -> eventually differentiate into endodermal cells
Day 16

60
Q

What happens to the cells that migrate through the primitive streak after the 1st wave? When? What do they form?

A

they fill the resulting space between the yolk sac and epiblast layer -> eventually differentiate into mesoderm cells

Day 17

extend cranially from primitive node to form notochordal process

61
Q

the mesoderm that is lateral to the midline in gastrulation becomes ->

A

paraxial, intermediate, and lateral plate mesoderm

62
Q

By day 18, lateral plate mesoderm has split into what two layers ->

A

somatic and splanchic mesoderm

63
Q

By day 19, what membranes and plate have formed?

A

oropharyngeal and cloacal

neural plate

64
Q

What has happened by day 20 with the notochordal process?

A

notochordal process fuses with endoderm to form notochordal plate

65
Q

What happens to the notochordal plate at wk 3->4 (Day 22)?

A

notochord plate separates from endoderm to form the solid notochord

66
Q

What cells form the lining of the yolk sac (not from germ layer)?

A

hypoblast cells