embryo most of midterm 1

what does the graafian follicle release into the fallopian tube during ovulation

secondary oocyte with the zona pellucida and the cumulus oophorus (corona radiata)

where does the graafian follicle release the secondary oocyte

into the fallopian tube

what is ovulation

the release from the oocyte from the graafian follicle

-during day 14 of menstrual cycle

is the oocyte haploid or diploid

haploid

how many chromosomes does the secondary oocyte have

23

what phase of meiosis is the secondary oocyte stuck in

metaphase 2

where is the secondary oocyte transported once it is released

gathered by fimbriae and swept into infundibulum of fallopian tube

when can the secondary oocyte finish meiosis

only if it gets fertilized by a spermatozoa

what must occur before the sperm can fertilize the egg

must pass through the three oocyte barriers

what are the three oocyte barriers

corona radiata

zona pellucida

vitelline membrane (plasma membrane)

what is the vitelline membrane of the oocyte covered with

microvilli

what two mechanisms helps the sperm get through the oocyte barriers

capacitation

acrosome reaction

what is the final step of sperm maturation

capacitation

when does capacitation start

when the sperm's plasma membrane contact the oviduct of the fallopian tube

what does sperm contact with the oviduct result in

release of unknown factors from the oviduct cells that soak into sperm and start capacitation

what begins capacitation

factors from the oviduct

what is the acrosome of the sperm

hood-like structure over head of sperm that is filled with lysosome-like enzymes for penetration of zone pellucida

what surrounds the entire sperm including the tail

plasma membrane

where is the nucleus of the sperm located

head

how many chromosomes does the sperm have

23

what happens in phase 1 of capacitation

sperm's plasma membrane rids cholesterol

what is the effect of cholesterol on capacitation and fertilization

usually blocks it

what happens in phase 2 of capacitation

acrosome rids its glycoproteins

what is the effect of glycoproteins on capacitation and fertilization

usually blocks it

capacitation causes sperm _______

hyperactivity

at what point is the process of capacitation done

once cholesterol and glycoproteins have been released

what happens in the hyperactive phase of sperm

tail wags more quickly and more powerfully --> more power to push through corona radiata and zona pellucida

what is the first barrier that sperm must go through

corona radiata

how thick is the corona radiata

2 or 3 cell layers thick

what is found in the space between the cell layers of the corona radiata

hyaluronic acid

________ sperm can easily swim right BETWEEN the cells of the corona radiata

capacitated

how does the the sperm travel through the hyaluronic acid rich matrix of the corona radiata

acrosome released hyaluronidase which cuts through the matrix

what is the zona pellucida made of

zona pellucida glycoproteins (ZP1, ZP2, ZP3, ZP4)

aka for zona pellucida glycoproteins

zona pellucida sperm binding protein

what can the ZPs act as

sperm receptors

what is the main receptor that incoming sperm attach to

ZP3

what part of the sperm attaches to ZP3

SED1 receptors (MFGE8)

GALT protein

what do mutations in either the SED1 or ZP3 receptors cause

infertility

what does binding of GALT to ZP3 cause

acrosome releases proteolytic enzyme acrosin

what does acrosin start

acrosome reaction

how does acrosin react with the zona pellucida

cuts between the cells and allows the sperm to push through

what does the sperm's tail provide as it passed through the zona pellucida

forward propulsion

what type of enzyme is acrosin

serine proteinase

where does the sperm go once it penetrates the zona pellucida

peri vitelline space

when does fertilization of the egg begin

once the sperm enters the peri vitelline space

how long does fertiization take to complete

24 hours

where does binding of sperm to the egg plasma membrane occur

areas of the membrane that are rich in microvilli

what is the main receptor found on the sperm head for binding to the egg plasma membrane

Izumo1

what are the main receptors found on the egg for binding of the plasma membrane to the sperm head

Juno and CD9

what triggers upregulation of oocyte's Juno and CD9

acrosin getting into oocyte's plasma membrane

what does mutation of Izumo1, Juno, or CD9 cause

infertility

what happens once the sperm binds to the egg's plasma membrane

sperm is swallowed and enters the cytosol of the egg

what is the mechanism of the sperm being taken up into the egg cytosol

endocytosis like

does the entire sperm get into the egg?

no, the sperm plasma membrane and mitochondria get stuck on the egg plasma membrane and slowly disintegrate

what is polyspermy

more than once sperm gets into the oocyte

polyspermy is almost always a _______ event

fatal

what two mechanisms prevent polyspermy

fast block polyspermy

slow block polyspermy

what happens in fast block polyspermy

within a few seconds of sperm and egg plasma membrane fusion the entire oocyte's plasma membrane undergoes a massive depolarization

how much is the oocyte's plasma membrane depolarized in fast block polyspermy

-70mV to +10mV

what does the depolarization of the oocyte's plasma membrane prevent

other spermatozoa from binding to the egg's plasma membrane

what does the sperm release into the egg's cytoplasm during slow block polyspermy

phoshpolipase C-zeta (PLCZ)

what does PLCZ do

binds to the rough endoplasmic reticulum and triggers release of several waves of calcium ion from the ER

what is the effect of calcium waves

-hits the nucleus and restarts secondary oocyte's second meiotic division

2

-causes special cytosolic cortical granules to fuse with the oocyte's plasma membrane and release contents into perivitelline space

where are cortical granules of the oocyte located

float in the cytosol under the plasma membrane of the oocyte

what molecules do cortical granules release into the perivitelline space

polysaccharides

proteolytic enzymes

where do polysaccharides go once they are released from the cortical granules

diffuse through the perivitelline space and soak into the zona pellucida

what is the effect of polysaccharides on the zona pellucida

makes it thick and stiff

what is the thickening and stiffening of the zona pellucida

zona reaction

how are the sperm affected by the zona reaction

they have difficulty getting through the thick and stiff zona pellucida

what form of polyspermy prevention causes the zona reaction

slow block polyspermy

where do the proteolytic enzymes from the cortical granules go once they are released

diffuse through the perivitelline space and soak into the zona pellucida

what is the effect of proteolytic enzymes on the zona pellucida

deforms the ZP3 molecules on the zona pellucida so that sperm cannot bind

what does completion of meiosis II result in

a mature oocyte that is haploid

secondary polar body

what is the fertilized oocyte called after meiosis II is completed

definitive oocyte or ootid

how many nuclei does the definitive oocyte have

two haploid nuclei

what cycle does the ootid enter

mitotic cell cycle

when do the two pronuclei merge together to form one nucleus in the definitive oocyte

when they finish interphase

what is the result of the formation of one nucleus in the definitive oocyte

single somatic cell that has 46 chromosomes

what does the definitive oocyte become once it has one nucleus

zygote

what stage of the cell cycle are all chromosomes found in for the zygote

prophase

when is fertilization complete

with the formation of the zygote

when do we enter the first stage of human development

once the zygote is made and fertilization is over

what is the first stage of human development

embryogenesis

aka for embryogenesis

organogenesis, embryonic period/stage

how long does embryogenesis run

first 8 weeks

how long is the second stage of human development

from week 9 through birth

what is the second stage of human development called

fetal period

what does the first cleavage of the zygote give us

the embryo (two blastomeres)

where are the two blastomeres located

contained within the original zona pellucida of the old secondary oocyte

what is the genetic count of each blastomere

diploid with 46 chromosomes

does the zona pellucida normally cleave

no

what happens if the zona pellucida cleaves

twins can form

what is made when the two blastomeres undergo cleavage again via the mitotic cell cycle

four celled embryo

where does the process of cleavage occur

as the fertilized egg is traveling down the fallopian tube

what propels the egg down the fallopian tube

peristalsis and cilia action

where do the cilia of the fallopian tube push the egg

toward the uterus

what is the fallopian tube lined with

ciliated simple columnar epithelia

why can you get some odd numbered embryo stages

the blastomeres aren't always the same size or synchronized to start division at the same time

up until what point are the blastomeres loosely arranged in the emrbyo's zona pellucida

the third round of cleavage --> eight cell stage

what is the process of compaction

blastomeres become more and more tightly packed together in the embryo reducing the volume they occupy