Fertilization and Gastrulation Flashcards

1
Q

What allows sperm to pass through the corona radiata?

A

hyaluronidase
mucosal proteins
mvmt of tail

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2
Q

What stage of development is only present during week 2?

A

hypoblast

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3
Q

What is the corona radiata?

A

layer of follicular cells from mom that surround the oocyte; the most superficial layer of ovum

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4
Q

What does primitive blood come from and where is it formed?

A

from extraembryonic splanchnic mesoderm

forms in wall of yolk sac

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5
Q

What is the prechordal plate?

A

part of hypoblast that eventually becomes the mouth and organizational center for the head

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6
Q

What are the basic steps of egg penetration?

A

capacitation
passage of sperm through corona radiata
penetration of zona pellucida

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7
Q

Where is the mitochondrial sheath on a sperm?

A

on middle piece of tail

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8
Q

What forms the male pronucleus?

What degrades from sperm?

A

cytoplasmic contents form pronucleus

tail and mitochondria degrade (mito dna only from mom)

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9
Q

In the obstetrical/gestational view, when does the calendar start?

A

Last menstrual period

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10
Q

What happens to the primary yolk sac?

A

splits into 2: secondary goes up against epiblast primary goes to opposite side (remnant of primary umbilical vesicle?)

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11
Q

What is the chorion?

A

3 layers:
extraembryonic somatic mesoderm
cytotrophoblast
syncytiotrophoblast

= one of the layers of placenta

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12
Q

What are the 3 parts of the sperm tail?

A

middle piece (with mitochondrial sheath)
principal piece
end piece

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13
Q

What is the extraembryonic somatic mesoderm?

A

cells that line the trophoblast and cover the amnion

produces the connecting stalk and chorion

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14
Q

What happens in week 1 of gestation?

A
Fertilization
Cleavage
Blastocyst
Inner cell mass
Implantation
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15
Q

What can hydatidiform moles turn into?

What percentage of them do this?

A

choriocarcinomas = malignant tumor

3-5%

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16
Q

When does the acrosomal reaction occur?

A

when the sperm touches the zona pellucida

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17
Q

What is a complete mole from?

A

fertilization of empty oocyte –> duplication of sperm

or: fertilization of empty oocyte by 2 sperm

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18
Q

What is the trophoblast? When does it occur?

A

Cells surrounding inner cell mass

day 5 –> degrades day 7

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19
Q

When does cleavage occur?

A

~30 hours after fertilization

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20
Q

What is the zona pellucida

A

meshwork of glycoproteins that surround the oocyte; just deep of corona radiata

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21
Q

What is the bilaminar disc and when does it form?

A

2 discs are of epiblast and primary yolk sac formed of hypoblast
forms in week 2

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22
Q

When is implantation?

A

day 6

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23
Q

What is a blastomere?

A

One of first few cells after fertilization

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24
Q

what are the 2 types of extraembryonic mesoderm?

A

somatic and splanchnic

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25
Q

What is the extraembryonic splanchnic mesoderm?

A

cells that line the yolk sac

produce primitive blood

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26
Q

What is a hydatidiform mole?

A

benign, giant thing of trophoblast that causes excessive amounts of hCG
can be partial or complete

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27
Q

Where do choriocarcinomas have a high likelihood to spread to? (6)

A
vagina
lungs
bone
brain
liver
intestines
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28
Q

What is the very basic structure of a sperm?

A

head
neck
tail

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29
Q

What does the trophoblast differentiate into?

A

cytotrophoblast

syncytiotrophoblast

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30
Q

What is placenta previa?

A

When placenta implants over cervical os

can be marginal, partial, or total

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31
Q

What is capacitation?

A

glycoprotein coat and seminal PM proteins removed from PM of sperm
allow acrosomal reaction to occur

32
Q

What is the extraembryonic coelom?

A

hollow cavity outside of the embryo

33
Q

Where does fertilization occur?

A

ampulla of fallopian tube

34
Q

In the ovulatory calendar, when is day 1?

A

Fertilization

35
Q

What are the derivatives of extraembryonic mesoderm?

A

connecting stalk
primitive blood
chorion

36
Q

What is the syncytiotrophoblast and what does it do?

A

multibucleated cells above embryoblast
responsible for implantation
releases hCG –> signals to body that you are pregnant

37
Q

What is the cortical reaction?

A

release of lysosomal enzymes from granules near oocyte pm –> change membrane potential –> inactivates sperm receptors on zona pellucida

38
Q

Where does extaembryonic mesoderm come from?

Where does it go?

A

cells pull off from hypoblast –> go and coat trophoblast

39
Q

What happens right after the sperm reaches the pm of the oocyte? (step 3)

A

plasma membranes fuse

head and tail of sperm ender oocyte

40
Q

When is the blastocyst stage?

What is it formed from?

A

day 5 - 7

morula cells –> fluid from uterus enters and makes cavity

41
Q

What is the acrosome and its importance?

A

on head of mature sperm

contains enzymes to penetrate egg

42
Q

What is the connecting stalk and what does it come from?

A

from extraembryonic somatic mesoderm

forms at embryonic pole and connects embryo to trophoblast

43
Q

What do you do with fertilized embryos that you don’t use in IVF?

A

cryopreserve

good for 21 yrs

44
Q

What is the female pronucleus? what does it fuse with?

A

nucleus of ovum after it completes meiosis II –> fuses w/ male pronucleus

45
Q

What happens in cleavage?

A

increase in cell number
decrease in cell size
embryo size unchanged
morula development

46
Q

What are the basic clinical features of a hydatidiform mole? (5)

A
high hCG
vaginal bleeding
pelvic pressure or pain
enlarged uterus
morning sickness
47
Q

What are the layers surrounding the ovum from outside in?

A

corona radiata
zona pellucida
perivitelline space

48
Q

What makes up the epiblast?

A

ectoderm
amnion
amniotic cavity

49
Q

What is the cytotrophoblast?

A

mitotically active stem cell layer surrounding embryoblast and blastocystic cavity

the placenta

50
Q

When is the morula stage? What does it look like?

A

day 3

looks like a bunch of grapes = 16-32 cells

51
Q

What is the zona reaction and when does it occur?

A

block to polyspermy

occurs once 1 sperm passes through zona pellucida to prevent other sperms to enter

52
Q

What is a partial mole from?

A

fertilization of normal oocyte by 2 sperms

53
Q

What is the perivitelline space?

A

layer just superficial of plasma membrane of the oocyte

54
Q

What must degrade for implantation?

At what stage does this occur?

A
zona pellucida
blastocyst stage (day 5-7)
55
Q

When does gastrulation occur?

A

week 3

56
Q

What does the primitive streak form from?

A

epiblast

57
Q

What are the 3 germ layers that form in gastrulation?

A

ectoderm
mesoderm
endoderm

58
Q

In what half of the embryo does the primitive streak form?

A

caudal half

59
Q

What types of tissues are in the cloacal membrane and the prechordal plate?
Why is this significant?

A

only endoderm and ectoderm

There is no blood supply, so membrane ruptures and opens, which is what you want

60
Q

What is a sacrococcygeal teratoma?

A

benign tumor that is a remnant of the primitive - contains all different types of tissues

61
Q

What is an orapharyngeal teratoma?

A

huge gross looking tumor coming out of the head of a fetus

we think it is either abnormal germ cell migration or remnant of primitive streak

62
Q

What is the primitive streak and what does it do?

A

fold in epiblast (which becomes ectoderm) where cells migrate down; ones at the bottom are endoderm, ones in the middle are mesoderm

63
Q

What is the fate of ectoderm?

A

skin
CNS
hair
nails

64
Q

What is the fate of mesoderm?

A

connective tissue: blood, muscle, bones
heart
spleen

65
Q

What is the fate of endoderm?

A

lungs
GI organs
bladder
glands

66
Q

Where is the notochord?

A

extends from primitive node anterior to prechordal plate (head/mouth)

67
Q

What is the notochord important for?

A

template for vertebral column (does not become spinal cord)

induces ectoderm above it to become neural tissue

68
Q

What tissue is the notochord made of?

where does it lie

A

mesoderm

in between endoderm and ectoderm

69
Q

When the notochord canal closes, what does it fuse with to form?

A

fuses with endoderm

forms notochordal plate

70
Q

What are chordomas?

What are they from?

A

Rare, slow-growing, yet aggressive tumors in skeleton; usually in skull and sacral regions
arise from remnants of notochord

71
Q

What is the allantois?

A

loop of endoderm formed from wall of yolk sac
at posterior midline
template for umbilical arteries and vein

72
Q

What does the allantois become that is important for the bladder?

A

urachus

73
Q

What are the 3 types of mesoderm?

A

Paraxial
Intermediate
Lateral plate

74
Q

What is the fate of paraxial mesoderm?

A

somites: muscle, skeleton, dermis

75
Q

What is the fate of intermediate mesoderm?

A

urogenital: kidneys and gonads

76
Q

What is the fate of lateral plate mesoderm?

A

connective tissue: blood, lymph, mesenteries, cardiovascular

77
Q

What is the intraembryonic coelom?

A

space in intermediate mesoderm that becomes body cavities