1st semifinal (Kiva) Flashcards
fertilization happens where most of the time? And does not ever happen where?
The usual site of fertilization is the ampulla of the uterine tube, its longest and widest part. If the oocyte is not
fertilized here, it slowly passes along the tube to the uterus, where it degenerates and is resorbed. Although
fertilization may occur in other parts of the tube, it does not occur in the uterus.
1, 2, 3
the head, containing the nucleus and acrosome on the head tip
the acrisome contains what and does what?
the enzyme released from the acrisome called Acrosin digests the zona pellucida and membrane of the oocyte.
also the penetration of the corona radiata is done by releasing hyaluronidase from the acrosome to digest cumulus cells surrounding the oocyte
4 and 5
the mid connecting piece and it contains many large fused mitochondria
the tail is called what?
it’s called the axial filament
what protein in the zona pellucida is responsible for binding the sperm?
zp3 bind the sperm, and is believed to only bind to human sperm. zp3 is also deactivated with the acrisome reaction
Part of the sperm’s cell membrane then fuses with the egg cell’s membrane, and the contents of the head sink into the egg. what happens next? what is this called?
slow block to polyspermy
after the fast block, the slow block to polyspermy is the Cortical Granule Response and release of enzymes that deactivate the ability for sperm to bind the zona pellucida
Part of the sperm’s cell membrane then fuses with the egg cell’s membrane, and the contents of the head sink into the egg. what happens next (immediately)? what is this called?
Fast block to polyspermy
Seconds after fertilization the membrane potential of the egg undergoes a large depolarization via a massive influx of Na+ ions. This depolarization is similar to a neuronal action potential in that it breaches voltage threshold, however, the egg’s depolarization takes about a minute to repolarize via K+ leakage. This is the fast block to polyspermy: sperm cannot fuse to a membrane that is not -70mV.
to avoid multiple sperm binding!!!
upon addition of the sperm dna, the egg is then called the _____.
once the egg begins to divide, the dividing cells are called ______.
the 2n egg is a zygote, and the dividing cells are called blastomeres.
after about 9 divisions, the blastomeres begin to undergo ______ for what reasons?
after around 12-30 divisions, the zygote is renamed what?
compaction, is probably mediated by cell surface
adhesion glycoproteins. Compaction permits greater cell-cell interaction
When there are 12-32 blastomeres, the developing human is called a morula. The morula forms 3 days after fertilization, and enters the uterus.
after entering the uterus, the morula begins to change. blastomere cells differentiate into what layers?
a fluid-filled space called the
blastocystic cavity appears inside the morula due apoptosis. The fluid passes from the uterine cavity through the zona pellucida to form this space. As fluid increases in the blastocystic cavity, it separates the blastomeres into 2 parts:
o Trophoblast (gives rise to embryonic part of placenta)
o Inner Cell Mass (Embryoblast) (gives rise to the embryo)
after blastogenesis, what happens to the blastocyst to allow further growth?
the blastocyst hatches from the zona pellucida (which is weak from the fertilization) and this allows rapid growth due to lack of the containing shell
after blastogenesis, two things happen. the cell mass differentiates and the trophoblasts differentiate
the Trophoblast starts to proliferate rapidly. It gradually differentiates into 2 layers:
o Cytotrophoblast
o Syncytiotrophoblast
after this…
Morphological changes occur in the embryoblast that result in the formation of a flat, almost circular bilaminar
plate of cells, called the embryonic disc, which consists of 2 layers:
o Epiblast – the thicker layer consisting of high columnar cells related to the amniotic cavity.
o Hypoblast – consisting of small cuboidal cells adjacent to the exocoelomic cavity.
The Syncytiotrophoblast are where and do what?
The Syncytiotrophoblast are on the outer layer of the blastocyte and produce enzymes that erode the maternal tissues, enabling the blastocyte to
burrow into the maternal endometrium.
the epiblast is important because it _____.
the epiblast cells give rise to the germ layers that form all the tissues and organs of the embryo.
1 and 5
Syncytiotrophoblast and Cytotrophoblast
9 and 8
amniotic cavity and exocoelomic (or yolk) sac/cavity
4 and 6
epiblast and hypoblast
cell layers noted by:
2
3
7
the amnion
the endometrium
exocoelomic membrane
1
lacunear network
2 and 4
- extra embryonic mesoderm
- primary umbilical vesicle/yolk sack
3
closing plug of the endometrium
the extraembryonic mesoderm becomes two layers later down the line and one very important sac
The extraembryonic coelom splits the extraembryonic
mesoderm into two layers
- Extraembryonic somatic mesoderm, lining the trophoblast and covering the amnion
- Extraembryonic splanchnic mesoderm, surrounding the umbilical vesicle
The extraembryonic somatic mesoderm and the two
layers of trophoblast form the chorion. The chorion
forms the wall of the chorionic sac
1, 2, 3
explain the arrows
- Primitive groove
- Primitive pit
- Primitive node
1+2+3 = primitive streak
epiblast cells migrate towards the primative streak caudally and then submerge and migrate back cranially.
the cells first displace the hypoblast and form the endoderm, then the cells left in the space between the ectoderm and endoderm form the mesoderm.
4 and 5
- the pre-chordal plate that gives rise to the endoderm of the oropharyngeal membrane, located at the future site of the oral cavity
- Cardiogenic plate, future heart
6, 7, 8
- Sectional edge of amniotic membrane
- Mesoderm
- Endoderm
9
Future cloacal membrane
Caudal to the primitive streak there is a circular area—
the cloacal membrane, which indicates the future site of
the anus
the notocord and notocordal process is formed how?
- The notochordal process elongates by invagination of cells from the primitive pit.
- The primitive pit extends into the notochordal process, forming a hollow notochordal canal
- The notochordal process is now a cellular tube that extends cranially from the primitive node to the prechordal plate.
how does completion of the notocord happen?
- The floor of the notochordal process (The fused layers with the underlying embryonic endoderm) gradually undergo degeneration
- the interior cells grow
- Beginning at the cranial end of the embryo, the notochordal cells proliferate and the notochordal
plate infolds to form the notochord
what are the somites? when do they begin to differentiate?
the somites are the paraxial mesoderm differentiates that begins to divide into paired cuboidal bodies (paraxial mesoderm that becomes segmented),
these begin to form at the same time as the notochord and neural tube form. the intraembryonic mesoderm on each side of them
proliferates to form a thick, longitudinal column of paraxial mesoderm
what are the most important things formed by the intermediate mesoderm?
kidneys,
ovaries and testis
Lateral mesoderm is where and is responsible for what? what are the three parts?
Lateral mesoderm is continuous with the extraembryonic mesoderm covering the yolk sac and amnion. There are two thick layers and a cavity on each side of the notocord that is known as the lateral mesoderm.
- *the cavity is the intraembryonic coelom** (the coelom represents the future serous cavity of the
trunk: peritoneal, pleural and pericardiac cavities). - *The somatopleure,** which is close to the ectoderm, is involved in the formation of the lateral and ventral walls of the embryo.
- *The splanchnopleure,** which lies on the endoblast, takes part in The formation of the wall of the digestive tube
1
yolk sac
2
amniotic cavity with amniotic fluid
3
amnion
4
endometrium
5, 6, 7
they become what?
5: endoderm
digestive system, pancreas, liver, inner layers of the lungs
6: mesoderm
circulatory system, out layer of lungs, skeletal system, genitourinary, muscles
7: ectoderm
skin, hair, nails, CNS,
8
allantois (allan-tow-is)
vestigial structure and may regress, yet the homologous blood vessels persist as the umbilical arteries and veins connecting the embryo with the placenta
9
chorion
10
maternal blood pool
in the placenta, what are chorionic villi? primary, secondary and tertiary?
projections of synciotiotrophoblast (exterior) and cytotrophoblast (interior) layers that hold the fetal vein and arteries and allow diffussion through the materanl blood pool
Shortly after primary chorionic villi appear at the end of
the second week, they begin to branch.
Early in the third week, mesenchyme grows into these primary villi, forming a core of mesenchymal tissue. The villi at this stage—secondary chorionic villi—cover the entire surface of thechorionic sac (Fig. 4-14A and B).
Some mesenchymal
cells in the villi soon differentiate into capillaries and
blood cells. Villi are called tertiary
chorionic villi when blood vessels are visible in them.
