Developmental Biology Flashcards
first 8 week of development in humans
embryonic development
all development after the first 8 weeks
fetal development
human gestation period is – days
266 (nine months)
embryonic development is complete within the – trimester
first
sperm have the ability to survive about – hours in the female system, while an egg cell only survives about – hours
48, 24
sperm deposited prior to or right after – are capable of fertilizing the egg, which occurs in the fallopian tubes
ovulation
200 to 500 million sperm are typically released during ejaculation but only – will make it to the egg cell
200
secretions from the female system will change the membrane composition of the sperm near its –
acrosome
When sperm bumps into the egg, the content of its acrosome will be released due to –
membrane instability
after the acrosome is released, sperm can penetrate the – of the egg
corona radiata (outer layer)
the first sperm to pass through the – will pass its nucleus into the egg
zona pellucida
after one sperm passes through the zona pellucida, the egg’s membrane will – which will make it impenetrable to fertilization by other sperm
depolarize
the nuclei of the egg and sperm fuse creating a
zygote
one day after fertilization, the zygote performs its first meiotic division, becoming
an embryo
rapid cell division characteristic of early embryonic development
cleavage
within about 4 days, the embryo reaches the – stage in which it consists of a ball of cells
morula stage
during early cleave, the embryo may split into two, which results in
identical twins
by about six days, the center of the embryo hollows out and becomes filled with fluid and is termed
blastula or blastocyst
outer cells of the blastocyst
trophoblast
aid in implantation and development of extra embryonic membranes and the placenta
trophoblast
the inner cell mass of the blastocyst is the source of – which have the ability to differentiate into any cell type
embryonic stem cells
implantation of the embryo begins about one after fertilization and is complete by the – week
second
blastocyst produces a critical hormone that is important for the maintenance of pregnancy –
human chorionic gonadotropin (HCG)
HCG is the signal to the – not to degrade
corpus luteum
normally, the degradation of the corpus luteum causes a decline in – and – and trigger menstruation
estrogen and progesterone
what forms during gastrulation?
the three primary germ layers
once a cell enters a germ layer, its ability to differentiate into specific cell types is –
limited
cells in this layer will express genes needed to become skin cells and nervous system cells
ectoderm
cells in this layer will express genes needed to become muscles, bones, and most internal organs
mesoderm
cells in this layer will express genes needed to become the lining of internal body cavities, respiratory, digestive, urinary, and reproductive tracts
endoderm
once gastrulation is complete, – begins the development of the nervous system
neuralization
– form the notochord
mesoderm cells
ectoderm above the notochord starts to thicken and folds inward, forming – that continue to deepen and fuse to produce a neural tube that will eventually develop into the CNS
neural folds
as differentiation continues, certain cells can influence the gene expression of other cells in the process of – via chemical messengers
induction
communication b/t cells is also used to establish – in the embryo, which is critical to the formation of internal organs as well as the limbs
positional information
– produce proteins that are essential for guiding the development of the shape of the embryo
homeobox genes
the proteins produced by the homeoboxes are - that serve to turn on specific genes within cells at specific times
transcription factors
– ensures that the right structures occur in the right places
induction
the separation of fingers and toes is the result of – of the cells at one time joined structures
apoptosis
organs are developed on an – basis with the most critical organs being produced first
as-needed
by the fourth week, the – are established and working
heart and limbs
all major organs are established and most are functioning by
the end of the embryonic development (8th week)
while the embryo is in the process of implanting into the endometrium, – will be formed outside of the embryo
four membranes
surrounds the embryo in a fluid-filled sac that serves a protective function and provides cushioning for the embryo and fetus
amnion
is a membrane that will ultimately form the umbilical cord
allantois
connection between the embryo and the placenta
umbilical cord
organ that will deliver nutrients and oxygen and remove CO2 and waste
placenta
where the 1st blood cells develop, in other species it serves as a source of nutrients
yolk sac
will eventually become the embryo’s side of the placenta
chorion
the – develops from the chorion and grows in size during development
placenta
fetal hemoglobin has – for oxygen than adult hemoglobin
a greater affinity
placenta produces – to maintain the pregnancy
HCG, estrogen, progesterone, and relaxin
the hormone relaxin releases the – that attach to the mother’s pubic bones to provide more space in the birth canal
ligaments
how long does it take for the placenta to fully develop
3 months
fetal development is primarily refinement of the – that are already established during embryonic development
organ systems
labor is triggered by the hormone – which is produced by the posterior pituitary gland
oxytocin
oxytocin cause contractions of the uterus to – with time
intensify
– usually ruptures during the dilation stage
amnion
once the cervix is dilated, contractions continue, leading to the
expulsion of the baby
after the baby is delivered, the – is clamped and cut, which severs the connection to the placenta
umbilical cord
finally, the – is delivered at the end of labor
placenta
