Reproduction Flashcards
During ejaculation, _____ sperm are ejected into the vagina, but _____ due
to leakage, destruction, or inability to penetrate the mucus of the cervix.
several hundred million; most
are lost
In order to be fertilized, the secondary oocyte must encounter a sperm within _____ of
ovulation. (Sperm can live in the female reproductive tract for up to _____.)
12 to 24 hours; 1 to 3 days
The secondary oocyte is protected by two structures, a cluster of cells called the _____
and a clear glycoprotein coat called the _____.
corona radiata; zona pellucida
To penetrate the egg, the acrosome of sperm must _____ to release _____. To prevent
early release, each sperm’s acrosome is inactive until _____.
rupture; digestive enzymes;
long after it enters the vagina
The acrosomes of sperm cannot rupture until they are exposed for several hours to fluids
in the vagina, uterus, and fallopian tubes. This preparation of the acrosome for use is
called _____.
capacitation
Only one sperm will actually fertilize the egg, but that one sperm needs the help of many
others in order to _____ so that it can reach the egg. Essentially, the egg’s defenses fail
when attacked by hundreds of sperm.
dissolve the zona pellucida
The membrane covering the acrosome contains receptors which bind to proteins of the
zona pellucida. This binding triggers the _____, which causes the _____.
acrosomal reaction; release of
digestive enzymes
The first sperm to penetrate the zona pellucida will bind to a receptor on the oocyte’s
membrane. This triggers two events: the first sperm _____, and other sperm are _____.
enters the oocyte’s cytoplasm;
blocked from entry
There are two mechanisms which prevent more than one sperm from entering an oocyte.
The first is the _____, which occurs when the membrane of the _____ and prevents
similar binding by other sperm cells.
fast block to polyspermy;
oocyte depolarizes
The _____ block to polyspermy results in the release of _____, which are specialized
vesicles. This leads to the denaturation of the zona pellucida’s proteins, including _____.
slow; cortical granules; the
receptors to which sperm bind
The entry of the sperm into the oocyte causes the oocyte to activate. As a result, it _____,
becoming the _____ and producing a small, cytoplasm-free cell, the second polar body.
(Recall that the first one was produced during _____.)
finishes meiosis II; ovum;
oogenesis
Inside the oocyte, the sperm’s head and tail separate. The sperm’s nucleus swells to form
the _____, and migrates to the center of the ovum where it joins with the _____ (which
was formed when the oocyte completed meiosis II).
male pronucleus; female
pronucleus
It’s not until the male and female _____ fuse to form a diploid nucleus that the joined
sperm and egg can be called a(n) _____ (which means _____).
pronuclei; zygote; fertilized,
diploid egg
Fertilization usually occurs in the _____ or _____ of the uterine tube; cell division begins
there, and continues until the growing mass of cells _____.
infundibulum; distal ampulla;
implants in the wall of the
uterus
Almost immediately after fertilization, the zygote begins to _____; a small, berry like
structure called the _____ is formed by day 3, and a hollow ball of cells called the _____
has been formed by day 4.
divide rapidly; morula;
blastocyst
The formation of the blastocyst is called _____.
blastulation
During pre-embryonic development, mitosis and cytokinesis occur without _____. This
process is called _____. As a result, the entire blastocyst, which contains ~100 or so cells,
is roughly _____ .
growth between divisions;
cleavage; the same size that
the ovum was
The blastocyst is a hollow ball. The outer wall is the _____, and the cluster of cells inside
is the _____.
trophoblast; inner cell mass
The cells of the _____ are still pluripotent, and can form any tissue or even complete
individuals.
inner cell mass
The trophoblast will eventually develop into the _____, while the inner cell mass will
eventually form one or more _____.
placenta and supporting
structures; embryos
The _____ reaches the uterus around four days after ovulation. It remains there as the
_____ breaks up, during which time it is nourished by uterine secretions.
blastocyst; zona pellucida
Implantation begins about 6–7 days after ovulation; in this process, the cells of the
trophoblast which are closest to the inner cell mass _____. This process continues until
the blastocyst is _____, and takes several days.
digest their way into the
endometrium; completely
embedded
To prevent menstruation, the cells of the blastocyst release _____ for the first _____
months of pregnancy. This promotes the survival of the corpus luteum until the placenta is
mature enough to produce large amounts of _____ and _____.
human chorionic gonadotropin
(hCG); four; progesterone;
estrogen
High levels of estrogen and progesterone can cause an unpleasant side effect in the early
months of pregnancy: _____.
morning sickness
The placenta is a temporary organ which forms in the uterus to allow the blood of the
mother and the unborn child to _____. It also acts as a(n) _____ to shield the fetus from
at least some harmful substances.
exchange chemicals and gases
without mixing; filter
Before implantation, the boundary between the inside of the blastocyst and the outside is
a single layer of cells called the _____. Eventually, cell division and differentiation lead to
a more complex boundary called the _____.
trophoblast; chorion
After implantation, trophoblast cells divide rapidly and the outermost cells _____. _____
grow from the surface, and become _____ as surrounding blood vessels are dissolved.
This is the very early _____.
fuse to form a syncytium; Villi;
bathed in maternal blood;
chorion
The placenta forms from the _____ and the _____ which lie between the embryo and the
wall of the uterus. The _____ in other regions deteriorate, forming the smooth chorion.
endometrium; chorionic villi;
chorionic villi
The placenta is fully functional by _____ .
the 3rd month after fertilization
The _____ connects the developing embryo to the placenta until birth.
umbilical cord
The _____ channels blood from the umbilical cord past the fetal liver, directly to the vena
cava.
ductus venosus
Together, the foramen ovale, ductus arteriosus, and ductus venosus are known as the
_____.
vascular shunts
The development of ectoderm, mesoderm, and endoderm from the _____ is called _____,
and the embryo is referred to as a(n) _____. All three layers are present roughly _____
after conception.
inner cell mass; gastrulation;
gastrula; 16 days
Early in gastrulation, a two-chambered ball of cells on a connecting stalk forms. One
chamber is the _____, and the other the _____: the wall between them is the _____, and
will actually form the embryo.
amnion; yolk sac; embryonic
disk
The _____ is a fluid-filled sac which will eventually surround the fetus. At first the fluid is
derived directly from the _____, but by birth much of its volume is _____. It provides
cushioning and support, and _____, during development.
amnion; maternal blood; fetal
urine; room to move