_____ is the joining of a haploid sperm nucleus and a haploid egg nucleus to form a diploid zygote
fertilization is the joining of a _____ sperm and a _____ egg to form a _____ zygote
haploid; haploid; diploid
_____ is the final maturation step for the sperm prior to fertilization
capacitation is triggered by secretions from the _____ wall
capacitation _____ the sperm's plasma membrane
what are the 2 main results of capacitation?
acrosomal reaction preparation and increased Ca2+ permeability
what is significant about increased Ca2+ permeability for a sperm after capacitation?
it causes hyperactivity, making the flagellum beat harder
the _____ is the recognition process between the sperm and the egg before they fuse together
the acrosomal reaction ensures _____ fertilization
the _____ is found on the tip of the sperm head, and it contains hydrolytic enzymes for digestion of the outer egg layers
the corona radiata _____ layer of the egg
the _____ is a jelly coat of follicular cells, which nourished the egg when it was developing in the follicle
the _____ is a layer of glycoproteins within the corona radiata
the vitelline layer surrounds the _____ of the egg
the vitelline layer is called the _____ in mammals
what are the 4 main zona pellucida proteins?
ZP1, ZP2, ZP3, ZP4
what does the zona pellucida protein (ZP3) do?
binds to sperm and stimulates the acrosome reaction
an egg's plasma membrane is found underneath the _____
zona pellucida (vitelline layer)
what is the general process of the acrosomal reaction?
sperm --> corona radiata --> zona pellucida --> sperm actin binds ZP3 --> acrosomal enzyme release --> membrane fusion between sperm and egg --> fertilization
_____ describes the process where more than 1 sperm fertilizes an egg
what would result from polyspermy?
polyploidy and a non-viable embryo
what do polyspermy blocks do?
prevent more than 1 sperm from penetrating into the egg
what are the 2 types of polyspermy blocks?
fast and slow block
the _____ block to polyspermy happens 1st, immediately after the sperm's membrane has fused with the egg's membrane
what is the general mechanism of the fast block to polyspermy?
egg penetration by sperm --> Na+ influx to egg --> membrane depolarization that repels additional sperm for a few seconds
the _____ block to polyspermy happens 2nd, gradually after the sperm has fused with the egg
the slow block to polyspermy is a _____ solution than the fast block
what is the general mechanism of the slow block?
sperm/egg membrane fusion --> fast block --> release of Ca2+ to egg membrane --> cortical reaction
which organelle releases the Ca2+ seen during the slow block to polyspermy?
the endoplasmic reticulum
what happens during the cortical reaction?
there is an exocytosis of cortical granules from the egg cell
_____ (slow block) stimulate proteases to sever the link between the zona pellucida and the plasma membrane, creating an impenetrable fertilization envelope
cortical granules (slow block) stimulate _____ to sever the link between the zona pellucida and the plasma membrane, creating an impenetrable _____
proteases; fertilization envelope
secondary oocyte's complete _____ after successful sperm penetration
_____ occur when 1 fertilization gives rise to 1 zygote, which then divides to form 2 separate embryos
monozygotic twins have the exact same _____, so they are identical
what is the general mechanism of dizygotic twin creation?
the mother ovulates 2 eggs --> both are individually fertilized by 2 different sperms --> 2 different zygotes with slightly different genetic material
dizygotic twins are _____ twins
what is the first step of growth after the formation of the zygote?
cleavage is rapid cell divisions that occur without changing the _____ of the embryo
in cleavage, each daughter cell has _____ cytoplasm than the mother cell
each small cell resulting from cleavage is called a _____
what are the 3 main ways to classify cleavage?
axis; cell fate; evenness of embryo division
classifications of cleavage based on axis can be _____ or _____
_____ cleavage results in cells aligned on the vertical axis with the top cells overlapping the bottom cells
radial cleavage results in cells aligned on the _____ axis with the top cells overlapping the bottom cells
deuterostomes undergo _____ cleavage
_____ cleavage results in misaligned cells that deviate away from the vertical axis
spiral cleavage results in _____ cells that deviate away from the vertical axis
misaligned (think spiral staircase)
protostomes undergo _____ cleavage
classifications of cleavage based on cell fate can be _____ or _____
_____ cleavage refers to blastomeres that have a decided fate after they are made through cleavage
_____ cleavage refers to blastomeres that do not have a pre-set fate
blastomeres from indeterminate cleavages can split off from the other blastomeres to form _____
a separate organism (identical twins)
classifications of cleavage based on evenness of embryo division can be _____ or _____
_____ cleavages happen through the entire embryo
holoblastic cleavages typically happen in embryos _____ a lot of yolk
what are some examples of embryos that go through holoblastic cleavages?
humans, sea urchins, frogs
_____ cleavages refer partial cleavage (the entire embryo does not evenly divide)
meroblastic cleavages usually happen in embryos _____ a lot of yolk
what are some examples of embryos that go through meroblastic cleavages?
birds, fish, reptiles
what does embryonic yolk do?
functions to provide nutrients to the growing embryo
embryos with _____ yolk exhibit polarity, containing an animal and vegetal pole
a lot of
embryos with a lot of yolk exhibit polarity, containing an _____ and _____ pole
_____ poles exhibit active cleavage
_____ poles exhibit slow/negligible cleavage because they contain a lot of yolk
frog embryos contain a significant amount of yolk, so they experience_____, yet_____, cleavages
the solid ball of roughly 12-16 blastomeres is called a _____
the _____ is a hollow cavity that begins to form around the 128 cell stage
when the hollow, fluid-filled blastocoel develops, the embryo is said to be a _____
which 2 structures result from further divisions and differentiation of the blastula?
trophoblast; inner cell mass (ICM)
when the inner cell mass (ICM) has developed, the blastula becomes a _____
the _____ is the outer ring of cells in the blastocyst
the _____ is the inner bulk of cells, which is surrounded by the trophoblast of the blastocyst
inner cell mass (ICM)
where does fertilization usually take place (in the female reproductive tract)?
in the oviduct (fallopian tube)
where does cleavage happen (in the female reproductive tract)?
when the fertilized egg travels toward the uterus (in the oviduct/fallopian tube)
what stage of the embryo implants into the uterine wall?
before a blastocyst can implant into the endometrium, it must get rid of its _____
_____ is when the blastocyst removes its zona pellucida and replaces it with trophoblast cells
what are the 3 main functions of the trophoblast?
extraembryonic membrane formation, uterine implantation, and HCG production
HCG from the trophoblast functions to maintain the _____
trophoblast HCG maintains the corpus luteum, which allows for the continual production of _____ & _____ to maintain the endometrium
the inner cell mass (ICM) develops into the _____ itself
the bilaminar stage creates a _____ within the blastocyst
what are the 2 layers of the bilaminar disk?
hypoblast and epiblast
the _____ of the bilaminar disk will partially contribute to the yolk sac
(the rest of the hypoblast that does not contribute to the yolk sac will undergo apoptosis)
the _____ of the bilaminar disk will contribute to the main embryo
epiblast cells thicken and roll inward to form a structure called the _____
the _____ defines the left-right, top-bottom axis for the developing embryo
the primitive streak is a crucial structure to begin the process of _____
gastrulation makes a _____ embryo, which has _____ germ layers
what are the 3 germ layers of a trilaminar embryo, from superficial to most deep?
ectoderm; mesoderm; endoderm
invagination along the primitive streak forms a _____, which initiates gastrulation
the _____ is a hollow cavity that forms as the blastopore deepens
the archenteron eventually forms the _____
the blastopore is the opening to the _____
what does the blastopore become in deuterostomes?
what does the blastopore become in protostomes?
the _____ is the outermost germ layer
the CNS; PNS; sensory parts of the ear, eye, and nose; epidermis layer of the skin, nails, and hair; mammary and sweat glands; pigmentation cells; jaw and teeth; adrenal medulla all arise from _____ tissue
the _____ is the middle germ layer
the skeletal bones; muscles; cardiovascular system; gonads; adrenal cortex; spleen; notochord all arise from _____ tissue
the _____ is the innermost germ layer
the lining of the digestive, respiratory, and excretory systems; PLTT (pancreas, liver, thyroid & parathyroid, thymus) all arise from _____ tissue
what is organogenesis?
formation of new organs
the _____ is derived from the mesoderm germ layer
animals in the _____ phylum have a notochord
does the notochord develop into the neural tube?
no - it simply induces the formation of the neural tube
the notochord induces the formation of the neural tube from _____ cells
(the neural tube is made from ectoderm)
neural crest cells are derived from _____ cells that roll off during neural tube formation
_____ migrate to different locations of the body - forming teeth, bones, skin pigmentation, etc.
neural crest cells
mesoderm cells contribute to 2 masses of cells on each side of the notochord, called _____
_____ cells contribute to 2 masses of cells on each side of the notochord, called somites
somites (2 masses) become the _____ and _____ associated with the axial skeleton
vertebrae; skeletal muscles
_____ have the potential to differentiate to different cell types
what are the 3 types of stem cell potency?
totipotent, pluripotent, multipotent
_____ stem cells can become any cell in the body
what are some examples of totipotent stem cells?
zygote, blastomeres of the morula
pluripotent stem cells can differentiate into any of the _____
3 germ layers
(ectoderm, mesoderm, endoderm)
what are some examples of pluripotent stem cells?
cells from the inner cell mass (embryonic stem cells)
_____ cells can only differentiate into a few cell types of a specific tissue type
what are some examples of multipotent stem cells?
hematopoietic stem cells, which can divide into many blood cell types
trophoblast cells of the blastocyst give rise to _____ membranes
what are the 4 main extraembryonic membranes?
amnion; chorion; allantois; yolk sac
monotremes are _____ that lay eggs
ex - platypus
_____ are mammals that carry their babies in a pouch
ex - kangaroo, koala
the _____ is the inner extraembryonic layer that is closest to the growing embryo
the _____ secretes fluid to cushion and protect the embryo from damage
amniotes are animals that have an amnion - what are some examples?
reptiles, mammals, birds
_____ do not contain an amnion
what are some examples of anamniotes?
fishes and amphibians
why don't anamniotes have an amnion?
they lay eggs in water, which provides a sufficient cushion
the _____ is the outer extraembryonic layer that surrounds the embryo
what are the functions of the chorion in placental mammals?
it forms the fetal half of the placenta
the _____ is a platform of exchange of gases, nutrients, and wastes between the fetus and the mother
the chorion lies right underneath the _____ in egg-laying animals
the _____ functions as a membrane for gas exchange in egg-laying animals
the _____ is a sac the buds off the archenteron, and it stores waste for disposal
what are the functions of the allantois in placental mammals?
it transports wastes from the fetus to the placenta, and it later becomes the umbilical cord - eventually, it becomes the urinary bladder in adults
the allantois initially stores _____ in egg laying animals
the _____ later fuses with the chorion to help with _____ in egg-laying animals
allantois; gas exchange
is the yolk sac extra- or intraembryonic?
is yolk extra- or intraembryonic?
the yolk sac contains yolk to provide _____ to the growing embryo
the yolk sac is the first location of fetal _____ formation in placental mammals
the yolk sac usually has a _____ function in placental mammals
in placental mammals, the yolk sac nourishes the fetus until the _____ is mature and ready to take over this role
what is the sole nutrient provider to a fetus from an egg-laying animal?
the yolk sac
the frog embryo has an _____ distribution of yolk
uneven (i.e., it has polarity)
frog embryos have an _____ pole and a _____ pole
the frog embryo experiences _____, _____ cleavage
the human embryo experiences _____, _____ cleavage
the animal pole is _____ in color than the vegetal pole for frog embryos
(the vegetal pole has more yolk, so it is more pale)
the _____ is a structure that appears at the opposite end of sperm entry during frog fertilization
the gray crescent is grey because the cytoplasm of the _____ pole and _____ pole mixes
dark animal; pale vegetal
do frog embryos have a primitive streak?
where does gastrulation begin in frog embryos?
dorsal lip of the blastopore
(frog embryos do not have a primitive streak)
the dorsal lip of the blastopore opens to the _____ of frog embryos
the dorsal lip of the blastopore forms at the site of the _____ in frog embryos
any cell from the first cleavage that receives a bit of the gray crescent can become a _____
full frog embryo
if an embryo develops within an egg, it needs a huge _____ because there is no direct connection to the mother via a _____
the chick embryo (egg) has a _____, which connects the yolk to the ends of the shell
what is the main function of the chalaza?
nutrient distribution to the entire embryo
the blastula of a chick embryo has a flattened shape due to the yolk pushing it up, hence it is called the _____
the blastodisc is analogous to which mammalian structure?
inner cell mass (ICM)
do chicks have a primitive streak? why or why not?
yes - due to the flattened shape of the blastodisc