Comparative Implantation and Placentation Flashcards
-process in which a developing embryo,
moving as a blastocyst through a uterus,
makes contact with the uterine wall and
remains attached to it until birth.
IMPLANTATION
STAGES OF IMPLANTATION
a. Hatching
b. Apposition
c. Adhesion
d.Invasion
- the blastocyst sheds its zona pellucida.
- aid of endometrial secretions
Hatching
blastocyst contacts the implantation site of the endometrium.
Apposition
trophoblast cells of the blastocyst attach to the receptive endometrial epithelium.
Adhesion
- invasive trophoblast cells cross the
endometrial epithelial basement
membrane and invade the endometrial stroma - humans and guinea pigs
Invasion
3 well-developed, mummified, and mineralized fetuses loosely attached to the omentum.
ABDOMINAL PREGNANCY
Membranous structure formed by apposition of the fetal chorioallantoic membrane and the maternal endometrium (decidua).
PLACENTA
*Parts of the Placenta
Fetal part= ______
- connects with the embryo through the umbilical cord.
chorion
*Parts of the Placenta
Maternal part= __________
- endometrium of maternal uterus
endometrium
Basic types of placenta
Choriovitelline/yolk sac placenta
Chorioallantoic placenta
when the fused vascular choriovitelline membranes become attached to the endometrium common in marsupials.
Choriovitelline/yolk sac placenta
chorioallantoic membrane becomes attached to the endometrium. definitive form of placentation in higher mammals.
it may be preceded by and co‐exist with a temporary choriovitelline placenta.
Chorioallantoic placenta
CLASSIFICATIONOF CHORIOALLANTOIC PLACENTATION
Diffuse
Cotyledonary
Zonary- complete/incomplete
Discoidal- single or double
Villi are distributed throughout the chorionic vesicle except the undilated ends.
Horse and pigs
Equine placenta- microcotyledonary (diffuse distribution of microplacentomes).
DIFFUSE PLACENTA
Villi form tiny oval or round areas called cotyledons all over the external surface of the chorionic vesicle, except the undilated ends.
Cotyledons attach to specific areas, caruncles, in the lining of the uterus.
A cotyledon and caruncle attached to it combine to form the placentome.
COTYLEDONARY PLACENTA
discrete area of interdigitation between a maternal caruncle and a
fetal cotyledon.
Placentome-
___: placentas consist of rows of relatively large placentomes
ruminant
Villi are concentrated in a wide zone that forms a belt around the chorionic vesicle.
Comple or incomplete.
ZONARY PLACENTA
*Zonary placenta
has a belt of villi surrounding the entire chorionic vesicle.
-Dogs and cats.
Complete zonary placenta
*Zonary placenta
has a belt of villi surrounding the entire chorionic vesicle.
- Bear, skunk, mink, weasel, ferret and raccoon.
Incomplete zonary placenta
Villi are concentrated in oval-shaped disks.
Single or double.
DISCOID PLACENTA
*Discoid placenta
has one disk located at one end of the chorionic vesicle
- Humans and rodents.
Single discoid placenta
*Discoid placenta
has two disks, each located on each side of the chorionic vesicle.
- Monkeys.
Double discoid placenta
*HISTOLOGICAL CLASSIFICATION OF PLACENTA
The trophoblast or chorionic epithelium and uterine epithelium remain in close contact but both retain their original layer eg. marsupials ,ungulates (pig & horses) & lemur.
Epithelio-chorial
*HISTOLOGICAL CLASSIFICATION OF PLACENTA
Chorionic villi erode the uterine wall, so that the uterine epithelium is ruptured and the chorionic villi comes in contact with the connective tissue of the uterine wall eg. sheep & cow (ruminants).
Syndesmo-chorial
*HISTOLOGICAL CLASSIFICATION OF PLACENTA
Both uterine epithelium and connective tissue is
eroded so that the chorionic villi comes in contact with endothelium of maternal blood vessel eg. dogs ,cats & other carnivores.
Endothelio-chorial
*HISTOLOGICAL CLASSIFICATION OF PLACENTA
Uterine epithelium , connective tissue and
endothelium all are eroded and the chorionic villi baths in the maternal blood eg. human.
Haemo-chorial
*HISTOLOGICAL CLASSIFICATION OF PLACENTA
Foetal capillaries lie freely in maternal blood eg. Rabbit.
Haemo-endothelial
uterine endometrium is sloughed off
during parturition.
- Carnivores, primates, humans,rodents.
- Ruminants: partially deciduate
Deciduate placenta
uterine endometrium remains intact
during parturition.
-Horse and pig.
Acediuate placenta-
*PLACENTAL HAEMOPHAGOUS ORGANS
the nutritional material supplied to the embryo from the circulating maternal blood.
Haemotrophe
*PLACENTAL HAEMOPHAGOUS ORGANS
products absorbed by the embryo from the endometrium.
Histotrophe
mild sedative to pregnant women caused severe developmental limb defects in humans.
Thalidomide-
Villi are distributed throughout the chorionic vesicle except the undilated ends.
Horse and pigs
DIFFUSE PLACENTA
-blastocyst burrows through the uterine epithelium to the uterine stroma where the embryo develops.
- primates and guinea pigs
Interstitial
implantation occurs at a site opposite to the attachment of the mesometrium.
Anti-mesometrial
involves the blastocyst becoming lodged in a uterine cleft with proliferation of the surrounding uterine mucosa.
rodents
Eccentric
In horses, cattle, sheep, pigs, dogs, cats and rabbits, fluid‐filled sacs surrounding the embryo expand so that the extra embryonic membranes become apposed to the endometrium and attach to it.
Most common form of attachment in mammals.
Centric/Superficial
- This accessory organ to the placenta grows, regresses and almost disappears as gestation approaches.
- Also called as hematomata, haemophagous organs, green/brown border.
PLACENTAL HAEMOPHAGOUS ORGANS
Multi-lobular structure is consisting of two relatively ____ and several smaller lobes.
All of the lobes are ____, and the larger lobes bind and extend from the ____ to the back of the embryo at the end of gestation.
large lobes
round
allantoic cavity
In the first half the hemophagous organ is a ____ structure, followed by an expanded and bulbous
These blood‐filled spaces are considered to be a source of ____ for the fetus.
tubular
iron
In dogs, haemophagous organs, which have a characteristic ____ appearance, are
present along the margins of the zone of attachment.
Smaller central haemophagous organs may also be present.
green
In cats, haemophagous organs, which have a ____ appearance, occur irregularly in the zonary area.
brown
