Topic.2.Development.powerpoint.2.1.Early-Development.comparisons.in.model.organisms Flashcards
Using a tadpole as an example, explain what each part would be for the following:
central, dorsal, left, right, anterior, posterior
belly would be the ventral
backside would be dorsal
head would be anterior
the tail would be posterior
right would be between anterior & dorsal
left would be between central and posterior
In frog embryos, sperm will always enter at the ___ pole
animal
In frog embryos, what triggers the rotation of the cell cortex which exposes the grey crescent?
sperm entry
In frog embryos, what are grey crescents?
They are exposed non pigmented cytoplasm, they mark the future dorsal side
T/F sperm enter on the dorsal side
False, sperm enter a side that reveals the grey crescent on the opposite side. The GC is on the dorsal side, so the opposite of the dorsal would be ventral.
In frogs, grey crescent has ____ needed for the normal development of blastomeres. They regulate ___ in eggs.
Cytoplasmic determinants; gene expression
what are blastomeres?
a cell formed by the cleavage of a fertilized ovum
What is the name of the first stage of early embryonic development
after fertilization in sea urchins?
Cleavage
What happens during cleavage stage in sea urchins?
miotic cell divisions with no significant (NO G1/G2)
It partitions the embryo into blastomeres(“smaller cells”)
In sea urchins, what two poles can you find?
Vegetal pole: region where yolk (nutrients) is concentrated
Animal pole: opposite to vegetal pole
What is the difference between cleavage of sea urchin and frogs?
Both have vegetal and animal poles, however, the distribution of yolk affects cleavage patterns in frog embryos. Frog embryos also have a cleavge furrow,
T/F sea urchins have smaller blastomeres at the animal pole
False, frogs have smaller blastomeres because the vegetal side pushes up on the grey crescent, making animal blastomeres very small
Compare cleavage in sea urchins vs frog
Sea urchins:
-yolk evenly distributed
-early cleavage results in cells of similar size
Frogs:
- yolk concentrated at vegetal pole
-cells at animal pole are smaller than those at vegetal
Each cell within the ___, is a called a blastomere
blastula
in sea urchins, what is the blastula stage?
-Produced after 5-7 cleavage divisions
-blastula consists of a hollow ball of cells with a fluid-filled cavity(or blastocoel)
What are the differences in blastula in a sea urchin and frog?
Sea urchin- blastocoel takes up most of the cell
frog- blastocoel takes up top of the blastula
holoblastic cleavage
frogs, mammals, sea urchins
cleavage furrow passes entirely through yolk
meroblastic cleavage
birds, fish, reptiles
too much yolk and furrow can’t pass through the yolk, only occurs in a small area
The embryo is called a blastula after it has divided a LOT. As cleavage continues, cells in ___ pole start dividing more rapidly than the __ pole. By the next day, continued cleavage has produced a hollow ball
of thousands of cells called the ____. With a fluid-filled cavity, called the ____
animal, vegetal, blastula, blastocoel
T/F: Once a blastula is formed, there are transcription of zygote genes.
False, must have at least 4000 to be able to do so in frog embryos
What allowed cleavage to take place which eventually makes a blastula?
Gene products(mRNA and proteins) deposited by the mother when she formed the egg
What is gastrulation?
reorganization of blastula into a multi-layered organism
-ectoderm(outer layer of embryo)
-mesoderm(middle layer of embryo)
-endoderm(inner layer of embryo)
Ectoderm
-epidermis of skin(sweat/hair)
-nervous and sensory systems
-pituitary gland and adrenal medulla
-jaws and teeth
-germ cells
Mesoderm
-skeletal and muscular systems
-circulatory
-excretory and reproductive system(except germ cell)
-dermis of skin
-adrenal cortex
Endoderm
-lining of the digestive tract and associated organs
-lining of respiratory/excretory/ reproductive
-thymus, thyroid, parathyroid gland
In frog embryos, how is the location of gastrulation initiation established?
Sperm entry point
Mesenchymal stem cells
multipotent, turn into lots of different cell types
In sea urchins: Mesodermal mesenchymal cells
migrate from vegetal pole to blastocoel, will secrete calcium carbonate to form internal skeleton
In SEA URCHINS: When primary mesenchyme cells begin to migrate, remaining cells of the vegetal plate ______ to form the archenteron (future gut).
invaginate
archenteron
future digestive tract formed during gastrulation running from vegetal to animal poles
In sea urchins:
The vegetal plate is made up of endodermal cells, meaning what structure is also made up of it?
archenteron (future digestive tube)
The filopodia job is to _ and _ the archenteron. They are cellular extensions that facilitate cell _ and _
contract and extend; attachment and migrate
The filopoida is made up of ____
mesenchymal cells
The point of invagination in sea urchin embryos is called
blastopore
In sea urchins: blastopore on vegetal pole will become ____
anus
What are two key features of frog gastrulation?
Blastopore: crease that forms on the dorsal side of late blastula
Dorsal lip: involuted region of the blastopore
during frog gastrulation, what happens when dorsal lip moves inward?
Animal pole cells spread over the outer surface of the embryo
In frog gastrulation, what happens after dorsal lip moves inward?
blastopore extends via invagination, making a circle and becomes an opening into the Archenteron
In frog gastrulation, the blastopore is plugged by___
yolk
In protosomes(worms), the blastopore is plugged by yolk and becomes the ___
mouth
In chick gastrulation, the embryo consists of what upper and lower layer?
Upper:epiblast
lower:hypoblast
T/F in chick gastulation, the embryo comes from the hypoblast
False, comes from the epiblast. The hypoblast cells form part of the sac that surrounds the yolk
In chick gastrulation, we can find a primitive streak, what is it?
thickening found at the midline due to a
concentration of migrating cells
In mammals, the blastula forms the ____in the next stage
of development
blastocyst
The blastula forms the blastocyst by__
cells in the blastula arrange themselves in two layers:
the inner cell mass, and an outer layer called the trophoblast.
Inner cell mass (ICM):
group of cells that develop into the embryo
Trophoblast:
outer epithelium of the blastocyst; eventually forms
the fetal portion of the placenta
In mammals, once the blastocyst reaches the uterus, how is it able to implant into endometrium?
Trophoblast: secretes enzymes that breakdown the lining of the uterus
(endometrium) to facilitate implantation
In mammals, after the blastocyst is able to implant(7 days) we should see the formation of _?
epiblast: formed by inner cell mass; gives rise to ect, meso, endoderm and gives rise to extraembryonic mesoderm
hypoblast: formed by inner cell mass; contributes to extra embryonic membranes (such as yolk sac)
In humans, day 10-11 and 13 what should we find?
extraembryonic membranes form days 10-11 and gastrulation begins day 13
In humans,During day 10-11 what extraembryonic membrane should we see forming?
Chorion: extraembryonic membrane between fetus and mother;
Is the fetal part of the placenta
Gives rise to chorionic villi: allow transfer of nutrients from maternal blood to fetal blood.
In humans after gastrulation we should see:
Amnion
chorion
ectoderm
mesoderm
endoderm
yolk sac
extraembryonic mesoderm-umbilical chord
allantios
Amnion:
Amnion: membrane that makes the amniotic sac; protection/cushion
Allantois:
sac-like structure, involved in nutrition and excretion, webbed with blood vessels, collects liquid waste from the
embryo, and exchanges gases used by the embryo
gastrulation has produced what 4 extraembryonic membrane
Amnion, yolk sac, allantois, chorion
Placenta:
temperorary organ that begins to develop after blastocyst implantation,
connects the developing
fetus to the uterine wall to
allow nutrient uptake, gas
exchange
Placenta made up of what 3 layers
Amnion: innermost placental layer surrounding the fetus
Allantois: the middle layer of the placenta
Chorion: outermost layer of the placenta, comes into contact
with the endometrium
Yolk sac:
membrane
outside the embryo,
connected by a tube
(the yolk stalk) through the
umbilical opening to the
embryo’s midgut; helps
with circulation;
