15.1- fertilization and embryonic development Flashcards
developmental changes are divided into what 2 stages
embryonic and fetal
embryonic period consists of ___
rapid cell division, organs form, supporting structures form
fetal period consists of
rapid growth, organs function, systems form
fertilization is AKA
conception
fertilization=
fusion of sperm and egg to form a single cell with 46 chromosomes (23 pairs)
how many chromosomes does a human have
46`
how many pairs of chromosomes does a human have
23
how does the egg travel down the oviduct (2)
peristalsis and cillia
after the egg is released during ovulation, how many days does it take to reach the uterus
4 days
how many hours does the egg have to get fertilized and where does it take place
24 hours
oviduct
what kills and/or loses many sperm (2)
the females acidic and some sperm travel into the wrong oviduct
what allows the sperm to enter the egg
enzymes located in the acrosome (head)
the egg is surrounded by which 2 layers
1- zona pellucida
2- corona radiata
what is the zona pellucida
clear layer of protein and carbs surrounding egg plasma membrane
what is the corona radiata
follicle cells surrounding the zona pellucida that nourish the egg in the ovary
sperm must break through which 2 layers to enter the egg
- zona pellucida
- corona radiata
what happens when one sperm enters the egg
one sperm enters- plasma membrane depolarizes- no more sperm can enter
what is a zygote
first diploid 2n pair
hows a zygote created
23 chromosomes from each gamete combine to form 23 chromosomes pairs
what happens during cleavage
the single celled zygote begins to divide but stays the same size (1 cell-2cells-4cells…)
what’s a structure composed of 16 undifferentiated cells called
morula
morula reaches the uterus ___ days after fertilization
4
morula fills with ____ to form a ___ ___ called the ___/____
fluid
hollow hole
blastocyst/blastula
2 layers of the blastocyst + functions
inner cell mass (developed into embryo)
trophoblast (outer layer…cont)
trophoblast turns into ___ which then turns into ___
turns into the chorion which helps form the placenta
implantation occurs on days ___
5-7
trophoblast secretes ___ which____
enzymes which digest a small hole in the endometrium
what happens once the trophoblast secretes enzymes (3)
- blastula sinks into the hole in endometrium with inner cell mass against the wall
- endometrium tries to heal wound therefore trapping the blastocyst
- implantation has occurred and the woman is now pregnant
what needs to be prevented in order for the blastocyst and endometrium to not be lost
menstruation
what do trophoblasts secrete to maintain corpus luteum
hCG (human chorionic gonadotropin)
hCG mimics LH meaning that ___
estrogen and progesterone levels remain high
what prevents menstruation
high estrogen and progesterone levels
during the second week the blastocyst becomes a ___
gastrula
___ forms between inner cell mass and trophoblast
amniotic cavity
the inner cell mass develops into what 3 primary germ layers
1- ectoderm
2- mesoderm-
3- endoderm
ectoderm=
skin and nerves
mesoderm=
middle layer
muscles, skeleton, reproductive, excretory and circulatory systems
endoderm=
digestive and respiratory systems
morphogenisis=
developing distinct structures that make up an organism via differentiation
organs are formed between weeks
3-8
what forms the mesoderm cells that will eventually become the skeleton
notochord
during the 3rd week what develops from the ectoderm and what will it become
neural tube developed and will become brain and spinal cord
4th week =(4)
rapid development
circulatory system, lungs and kidneys, head+facial features
5th week= (3)
head grows, eyes open, brain quickly develops
6th week=(3)
brain continues to develop
arms and legs grow
gonads produce hormones to developed external genitals
7th and 8th weeks= (4)
organs form
nervous systems become active
skeleton has developed
cant tell sex yet (genitals aren’t fully developed)
after 8 weeks its now considered a ____
fetus
yolk sac is attached to ___
attached to abdomen of embryo
yolk sac fuction (2)
produces first blood cells and future egg and sperm
involved in forming digestive system
Amnion function (2)
lines amniotic cavity and produces fluid to cushion embryo, maintain temp. and provide space for developement
breaks before birth “water breaking”
allantoil function
forms umbilical cord
chorion function
forms fetal part of placenta
placenta is part of the __ and attaches ___ to ____
chorion and attaches embryo/fetus to uterine wall
placenta function (2)
attaches embryo/fetus to uterine wall to allow metabolic exchange with mother (hormones nutrients antibodies etc can travel)
secretes estrogen, progesterone and hCG
Umbilical cord contains __ arteries and __ veins
2 arteries 1 vein
arteries of umbilical cord carry
deoxygenated blood away from fetus
vein of umbilical cord carrys
oxygenated blood towards fetus
