reproduction; fertilization and fetal development Flashcards
internal fertilization advantages
- increases chance that gametes will meet = species have to produce fewer gametes
- fertilized ovum can be enclosed in a protective covering»_space; remains in female’s body during dvlpmt
human fertilization 1- fertilization moment?
fertilization = moment sperm cells f u s e s w/ secondary oocyte to form zygote
occurs in the oviducts of female
human fertilization 2- what is it designed to prevent?
its process is meant to prevent polyspermy» entry of more than one sperm cell nuclei
sperm only has __________ to reach _______________ _____
3-5 days, ovulated eggs (there’s two paths of two eggs, only one of them is ovulated at a time)
steps of fertilization 1- large number of what enters vagina? how much of it made it through?
large number of sperm are ejaculated into vagina during copulation
only a small number make it through cervix and uterus
steps of fertilization 2- acrosome reaction:
sperm binds to zona pellucida, contents of acrosome are released , enzymes digest zona pellucida
steps of fertilization 2.2- zona pellucida
secondary oocyte = surrounded by zona pellucida
zona pellucida = glycoprotein coat that prevents polyspermy
steps of fertilization 2.3- acrosome
a sac of enzymes contained in the head of sperm
steps of fertilization 3- penetration of the egg membrane
> > acrosome reaction exposes an area of membrane on the sperm w/ proteins that can bind to egg membrane
»_space; the first sperm that gets through binds it’s membrane with egg’s
membrane/ sperm nuclei enters egg cell
steps of fertilization 4- cortical reaction
sperm entry = activates egg
contents of c o r t i c a l g r a n u l e s = released from egg
> results in binding proteins on egg membrane = digested so sperm
can’t bind
also results in the hardening of the zona pellucida
blastocyst pt 1- what is travelling after fertilization + where to where?
after fertilization, zygote travels down oviduct towards the uterus
blastocyst pt 2- what does zygote do + when does it reach uterus, how does it end up?
as zygote travels, it begins the process: mitosis with series of divisions
zygote reaches uterus 24-36 hours later: now it’s almost a hallow ball of
cells called blastocyst
blastocyst pt 3- how will blastocyst form?
outer cells of blastocyst will become the placenta, while inner mass becomes embryo
blastocyst begins what? what does it do?
blastocyst -> i m p l a n t a t i o n : 6-10 days after fertilization, blastocyst attaches itself to the endometrium lining
implantation 1- what happens after ___________ is implanted?
when blastocyst is implanted, it secretes: HCG
implantation 2- HCG what does it do?
travels in blood stream + affects ovary which maintains the corpus luteum
implantation 3- what does the corpus luteum do?
produces progesterone + estrogen though the first trimester, @ this stage it’s called zygote»_space; e m b r y o
embryo dvlpmt 1- what happens in the second week of pregnancy? what’s the process called?
in the second week of being preg» cells begin starts to specialize, this process is called gastrulation which produces a gastrula
embryo dvlpmt 1.2- gastrulation + gastrula
during this cells in embryo become arranged in 3 layers = germ layers
} gastrula is the embryo at this stage composed of these 3 germ layers
embryo dvlpmt 2- how are germ layers positioned?
cells move to specific position to produce layers:
ectoderm
mesoderm
endoderm
embryo dvlpmt 2.2.1- ectoderm
forms skin + nervous system
embryo dvlpmt 2.2.2- mesoderm
forms kindeys, skeleton, muscles, blood vessels, and gonads
embryo dvlpmt 2.2.3- endoderm
forms the lungs and the lining of digestive tract
embryo dvlpmt 3- what is formed during the 10th to fourteenth day of pregnancy
between 10-14 days of pregnancy, outer portions of embryo form 4 parts
yolk sac
amnion
allantois
chorion
embryo dvlpmt 3.2.1- yolk sac
supplies nutrients for the first two months of development
embryo dvlpmt 3.2.2- amnion
fluid filled sac that protects the embryo
+ does cellular respiration
embryo dvlpmt 3.2.3- allantois
removes waste
embryo dvlpmt 3.2.4- chorion
surrounds everything
embryo dvlpmt 3.3- amniotic sac and fluid?
amniotic sac = sac where the baby is developed created by the membranes: amnion and chorion
amniotic fluid = the fluid within the sac that surrounds the baby and provides its nutrients.
what are gonads?
ovaries and the testicles } the reproductive systems of females and males
depending on the location of cells, are the genes on or off? why?
no genes are not always on depending on the cell»_space; different genes are needed for different areas of the body. it will turn on or off depending on the location/body part that c h e m i c a l s i g n a l s tell them to create.
what is the purpose of the placenta?
responsible for delivering nutrients and waste for developing fetus
what in our parts in our body make up the placenta?
placenta’s made up of maternal endometrium + small projections from chorion surrounding embryo: chorionic villi
after the first three months what happens to placenta?
placenta fully dvlps and begin producing p l a c e n t a l estrogen and progesterone to m a i n t a i n p r e g n a n c y
cv a- what is the chorionic villi’s (cv) main purpose?
to provide a l a r g e s u r f a c e a r e a for exchange of nutrients and waste between mother’s and fetus’ blood.
cv b- where does the fetal blood remain? what does this allow?
fetal blood remains in the capillaries of the chorionic villi = surrounded by maternal blood flowing into endometrial spaces
allows mom’s blood to be as close as possible to the baby’s without
having any actual contact
ubc a- umbilical cord, what is it attached to? how does this attachment function for fetus (like the pulmonary stuff)?
umbilical cord is how the embryo is attached to placenta
; fetal blood is carried to placenta by t w o umbilical arteries and carried back to the fetus by a s i n g l e umbilical vein
ubc b- what do umbilical arteries do?
umbilical arteries divide into capillaries within chorionic villi
ubc c- how do nutrients and o2 cycle
nutrients and oxygen d i f f u s e from mother’s blood into fetus
while waste and carbon dioxide diffuse from fetus to mother’s blood
gestation 1- what is gestation?
human gestation period = 40 weeks, divided into 3 block of time called trimesters
gestation 2 - what are trimesters? how much do we have?
each trimester lasts 3 months with major developmental changes occurring in every trimester
first trimester
second trimester
third trimester
} 3 trimesters in total
gestation 2.2.1a- first trimester dvlpmt
@6 weeks»_space; limbs, eyes, spine begin to form
@9 weeks» first bone cells form embryo + called a f e t u s
@ 12 weeks» all major organs have begun to develop: liver, brain, stomach, and heart
gestation 2.2.1b- first trimester, what’s the size of baby? what can we identify from the baby? what events effect baby?
@ 12 weeks»_space;fetus is 100mm long, has noticeable head and limbs
sex can be determined via ultrasound
embryo is most vulnerable to outside influences
gestation 2.2.2a- second trimester dvlpmt
@16 weeks» skeleton begins to form= brain grows rapidly + nervous system begins to form
@24 weeks» fetus = 300mm long+ fetus becomes more active + all organs are formed but not fully developed.
gestation 2.2.2b- second trimester what events effect the baby?
fetus can use its muscles to move spontaneously
gestation 2.2.3a - third trimester dvlpmt
@26-40 weeks» there’s a rapid increase in size: vital brain tissue is built + nervous system develops
gestation 2.2.3b- third trimester what events effect the baby?
fetus can survive outside the uterus w/ medical assistance’
fetus weighs more than 3000 grams
fetus becomes oriented head-down
risks factors during dvlpmt – first trimester fetus
1- anything mother eats, drinks, inhales end up in her blood + cigarette
smoke constricts fetal blood vessels preventing it from getting enough oxygen.
alcohol affects the functioning of its brain + central nervous system as well as physical dvlpmt
risk factors during dvlpmt– age
mom under 20 = increased chance of delivering premature baby
mom over 45 = 1/20 chance of having baby with c h r o m o s o m a l disabilities
risk factors during dvlpmt- other factors
-radiation
-pollutants
-mercury
