Lesson 9 Flashcards
Upon entering the uterine cavity, the embryo
is initially nourished by secretions from?
uterine glands or endometrial glands
These secretion products are called?
histotrophe or uterine milk
Histotrophe is not enough to nourish the embryo so to counteract it, the embryonic tissues
establishes close connections with the?
maternal circulatory system
the embryo to import bloodborne
maternal nutrients called?
hemotrophe
histotrophe and hemotrophe are
referred to as?
embryotrophe
To accomplish exchange between the mother
and her embryo a temporary organ is formed and is known as?
placenta
In what species, where the newly hatched
blastocyst attaches to the endometrial
epithelium and, the embryo actually
penetrates the epithelium and invades the endometrial connective tissue which it becomes completely embedded.
rodents and primates
the embryo leaves the
uterine lumen, and this process is called?
implantation
In domestic animals invasion of the
endometrium does not occur. True or False?
True
The embryo remains attached to the internal
endometrial surface throughout what period?
Gestation
What happens to the embryo after blastulation in most domestic species?
It reaches the uterine cavity before blastulation begins
What two structures does the inner cell mass differentiate into after hatching from the zona pellucida?
The epiblast and hypoblast
What are the two main components of the embryo at the end of blastulation?
The trophectoderm and the inner cell mass
What is the enclosed cavity that forms during early development called?
The primitive yolk sac
What happens to the extra-embryonic mesoderm during gastrulation?
It splits into somatic and visceral sheets.
What forms from the body foldings of the embryo during gastrulation?
The primitive gut and the definitive yolk sac.
Which structure fuses with the chorion to establish the choriovitelline placenta in some species?
The definitive yolk sac.
What structure develops as an evagination from the hindgut?
The allantois.
Which two structures fuse to form the chorioallantois, which gives rise to the chorioallantoic placenta?
The allantoic wall and the chorion
What two hormones are primarily involved in preparing the uterus for placentation?
Estrogens and progesterone
Which hormone produced by the corpus luteum stimulates the endometrium to synthesize prostaglandins (PGF2α), causing luteolysis?
Oxytocin
Which hormone predominates during metestrus and diestrus, preparing the uterus for embryo implantation?
Progesterone
What process is required to prevent luteolysis and maintain pregnancy?
Maternal recognition of pregnancy
What substance does the embryo in ruminants produce to block the formation of oxytocin receptors?
Interferon-tau (IFN-t).
How many embryos must be present in pigs to prevent luteolysis?
At least four embryos.
What strategy do pigs use to prevent luteolysis?
They secrete estradiol from their trophectoderm, which causes PGF2α to be rerouted into the uterine lumen for degradation.
In which two species is a functional choriovitelline placenta seen?
Carnivores and horses
Which two types of placentas are classified based on their fusion with extraembryonic structures?
Choriovitelline placenta and chorioallantoic placenta
Which placenta type is the primary functional placenta in all domestic species?
The chorioallantoic placenta
Which two types of placentas are based on the distribution of the chorion frondosum?
Diffuse placenta and cotyledonary placenta
What is the structure formed when chorionic villi combine with caruncles in the endometrium in ruminants?
Placentomes
What is the type of placenta seen in carnivores, where the chorion frondosum is organized into a broad belt?
Zonary and lamellar placenta
Which species have an epitheliochorial placenta?
Pigs, horses, and ruminants.
Which type of placenta retains all six layers of maternal and fetal tissues?
Epitheliochorial placenta
What type of placenta is seen in ruminants, where some trophoblast cells fuse with maternal epithelial cells?
Synepitheliochorial placenta.
How many layers are retained in the endotheliochorial placenta seen in carnivores?
Four layers.
Which type of placenta is the most invasive, involving the loss of all maternal tissue layers?
Hemochorial placenta.
In which species is the hemochorial placenta found?
Rodents and humans.
Which type of placentation involves the sloughing off of the uterine endometrium during parturition?
Deciduate placentation.
Which species exhibit deciduate placentation?
Carnivores, primates, and rodents.
Which type of placentation occurs when the uterine endometrium remains intact during parturition?
Adeciduate placentation.
Which species have adeciduate placentation?
Ruminants (partial), horses, and pigs.
What is the function of the trophoblast in early embryo development?
Form the outer layer of the blastocyst and later contribute to placental formation.
What does the extra-embryonic coelom surround during placental development?
It surrounds the expanding allantois and the embryo.
What is the significance of the fusion between the definitive yolk sac and the chorion in some species?
It helps establish the choriovitelline placenta, which is functional in species like carnivores and horses.
Which hormone is essential for the maintenance of early pregnancy by preventing luteolysis?
Progesterone, primarily produced by the corpus luteum.
How does the presence of interferon-tau (IFN-t) in ruminants help maintain pregnancy?
inhibits the formation of oxytocin receptors, preventing luteolysis and sustaining progesterone levels.
Why is PGF2α important in the context of maternal recognition of pregnancy?
It triggers luteolysis, which would lead to the regression of the corpus luteum and termination of pregnancy if not prevented.
Which species exhibit non-invasive placentation, where the embryo does not invade the maternal endometrium?
Most domestic animals, except for carnivores.
What are the main components of the placental barrier in the chorioallantoic placenta?
The endothelium, chorioallantoic mesenchyme, and chorionic epithelium
What is the difference between chorion frondosum and chorion laeve?
Chorion frondosum is where placental exchange occurs, while chorion laeve is the smooth part not involved in placental formation.
What specific signal does the embryo use in pigs to alter the secretion of PGF2α during maternal recognition?
The production of estradiol by the trophectoderm around Days 11-12 of development.
In the endotheliochorial placenta, which two maternal tissue layers are lost?
The endometrial epithelium and connective tissue are lost, leaving only the maternal endothelium in contact with the trophoblast.
allantois develops as an ___ from the ____
evagination - hindgut
As the embryo grows, the allantois gradually
expands into -?
extra-embryonic coelom
High levels of ____ are secreted into the
____ during proestrus and estrus.
estrogen - bloodstream
_____ predominates during the
following periods of metestrus and diestrus
when the early embryo moves from the
_____ into the____.
Progesterone - oviduct into the uterus
in what animal the corpus luteum produces
oxytocin as well as progesterone?
Ruminants
If the ___ attaches to the uterus, its ____ will produce interferon-tau (IFN-t), which will inhibit the formation of ____ ____ receptors.
blastocyst - trophectoderm - endometrial oxytocin
T OR F?
Then in the presence of an embryo, oxytocin
cannot stimulate the synthesis of PGF2α and luteolysis is prevented.
True
Pigs employ another strategy to interrupt the luteolytic pathway.
Estradiol is produced from their ______ around the days __ to __ of development.
trophectoderm - day 11 to 12
On swine, it causes PGF2α to be secreted into the ____ instead of into the maternal
blood stream.
uterine lumen into
A type of placenta where the yolk sac wall combines locally with the chorion to form an area for exchange.
Choriovitelline placenta
The region where the chorioallantois interacts with the endometrium to form placental structures.
Chorion frondosum
The primary functional placenta in all domestic species, formed by fusion between the allantoic wall and chorion.
Chorioallantoic placenta
A smooth surface area on the chorioallantois that does not engage in placental formation.
Chorion laeve
A structure formed in ruminants by the combination of cotyledons and caruncles in the endometrium.
Placentome
A type of placenta where the chorion frondosum is diffusely distributed over the entire chorioallantoic surface, seen in pigs and horses.
Diffuse placenta
A type of placenta in ruminants where chorion frondosum is organized into macroscopically visible tufts called cotyledons.
Cotyledonary placenta
A type of placenta in carnivores where chorion frondosum forms a broad belt around the embryo’s longitudinal axis.
Zonary placenta
The classification based on the number of tissue layers separating fetal and maternal circulations.
Placental barrier
A placentation type found in pigs, horses, and ruminants where no maternal tissue layers are lost, retaining all six layers.
Epitheliochorial placenta
A modified epitheliochorial placenta in ruminants where some trophoblast cells fuse with endometrial epithelial cells, retaining five layers.
Synepitheliochorial (or Syndesmochorial) placenta
A placental type found in carnivores where endometrial epithelium and connective tissue are lost, retaining four layers.
Endotheliochorial placenta
The most invasive placental type where all maternal tissue layers are lost, allowing direct contact with maternal blood. Seen in rodents and humans.
Hemochorial placenta
A classification based on whether the uterine endometrium is sloughed off during parturition.
Deciduate placenta
A type of placentation where the uterine endometrium remains intact during parturition, partially seen in ruminants, horses, and pigs.
Adeciduate placenta
The classification describing a placenta with no maternal tissue layer intact, as seen in rodents and primates.
Hemochorial
A specific type of placenta in carnivores where connective tissue and endometrial epithelium are lost, but endothelial layers remain.
Endotheliochorial
The classification term referring to a placenta with layers intact in maternal and fetal tissues, characteristic of species such as pigs, horses, and ruminants.
Epitheliochorial
The layer of cells derived from the chorion in the fetal part of the placenta that interacts with maternal tissue.
Trophoblast
The vascularized maternal tissue that combines with the fetal cotyledons to form placentomes in ruminants.
Caruncles
A specific placental structure formed by the fusion of chorionic villi into larger tufts in ruminants.
Cotyledons
Specialized trophoblast cells in ruminants that fuse with endometrial epithelial cells to modify the epitheliochorial placenta.
Binucleate cells
The term used for connective tissue found within the fetal part of the chorioallantoic placenta, originating from fused somatic and visceral mesoderm.
Chorioallantoic mesenchyme
: The cell type lining the fetal blood vessels in the chorioallantoic placenta.
Endothelium
The outermost layer of the fetal side of the placenta, consisting of trophoblast cells.
Chorionic epithelium
