Implantation and Placental Development Flashcards
embryo?
organism in early stages of development which has not yet acquired anatomical form making it recognizable as a specific species
fetus?
potential offspring that is generally recognizable as a member of a given species
conceptus?
the products of conception: 1) the embryo during early stages 2) the embryo and extraembryonic membranes during preimplantation stage and 3) the fetus and placenta during postattachment stages
___ make up the fetal side of the placenta in farm animals.
fetal extraembryonic membranes
What are the 5 fetal extraembryonic membranes?
chorion; allantois; umbilical cord; amnion; yolk sac
chorion?
encloses embryo and all other extraembryonic membranes.
What is the site of attachment to the uterus composed of?
mesoderm and trophectoderm (produce hormones)
allantois?
contains blood vessels that connect fetal circulation with placental circulation.
An outgrowth of the hind gut that fuses with the chorion forms ____ which is composed of the mesoderm and endoderm.
chorioallantois placenta
In humans ___ regresses after formation leaving allantois blood vessels in the umbilical cord which infiltrates the chroion.
allantois
umbilical cord?
encloses allantoic blood vessels and forms the vascular link between the mother and fetus
amnion?
fluid-filled sac that encloses the fetus and provides stability and protection, supplies water and other materials from amniotic fluid
In humans __ will fuse with the chorion.
amnion
amniocentesis?
in humans, a procedure to check for sex of fetus: small needle inserted into amnion and fluid extracted (genetic disorders indicated as well) - diagnostic test for abnormalities in fetal cells as well as sex
yolk sac?
develops early, lines trophoblast and blastocoele cavity. Early, it provides red blood cells and primordial germ cells and serum-like proteins as it serves a function similar to the liver.
__ regresses with fetal development.
yolk sac
From inside out, what are the layers for the differentiation of conceptus cell types?
primative gut, endoderm, mesoderm, trophectoderm, inner cell mass, ectoderm
In order from inside out, what are the layers of the extraembyronic membranes?
yolk sac, endoderm, mesoderm, ectoderm, chorion; formation of embryo, allantoic cavity, allantois, amnion, chorion
What are the four placental membranes?
chorion, yolk sac, amnion, allantois
The blood vessels that form are connected to the fetus through the ___.
umbilical cord
___ expands to fill the chorion.
allantoic cavity
What occurs prior to implantation?
blastocyst is bathed in uterine secretions and draws upon them for growth and survival; accumulation of organic molecules and ions by active cellular transport; exchanges of CO2 and O2 by simple diffusion
T/F: This is a limit to the size a free living conceptus can obtain before the CO2 and O2 exchange mechanism can become inadequate.
T
placenta?
zone of highly vascular contact between mother and conceptus, where two discrete ciruculations lie in close contact for rapid and efficient transfer of materials
What are the two types of implantation?
invasive; noninvasive
invasive implantation?
conceptus breaks through surface endometrial eptithelium and invades underlying stroma
noninvasive implantation?
endometrial epithelium is retained (or at least breached only sporadically, transiently, or much later)
What is the mechanism of the trophoblast and luminal epithelium attachment?
through physical contact by interlocking microvilli
___ attachment induces vascularization and differentiation of underlying stroma.
invasive
Decidualization of the uterus occurs during __ implantation.
invasive
What is decidualization?
1) edema - bumps full of blood form on uterus 2) changes in stromal cell morphology 3) sprouting and growth of capillaries in endometrium 4) decidua
decidua?
endometrial component of placenta; the place where implantation takes place in species that undergo decidualization
Trophoblast cells migrate and invade stroma in __ implantation.
invasive
cytotrophoblast?
unicellular trophoblast cells (one cell, one nucleus)
synctiotrophoblast?
fused cells which form a structure call the syncytium (fusing together makes gonadotropins)
The uterine gland and stromal tissue adjacent to invading trophoblasts are destroyed, taken up and utilized by the conceptus (passed to developing blood vascular system and distributed to growing embryo) in __ implantation.
invasive
interstitial invasion?
stroma is invaded so deeply that uterine epithelium grows back over conceptus (human, chimp)
eccentric invasion?
secondary contact with uterine epithelium on side opposite where implantation initiated - may result in two sites of placental development (bidiscoid placenta of rhesus, zonary placenta (dog, cat)
What three factors contribute to noninvasive implantation?
1) attachment initiated relatively late 2) prolonged free living period 3) great outgrowth of trophoblast
placentation?
a term often used to describe noninvasive implantation
chroionic villi?
projections on chorion that contact (interdigitate) with uterine tissue to bring fetal blood vessels in close proximity to maternal blood vessels
What are the 5 ways that the placenta is classified by shape?
1) cotyledonary 2) diffuse 3) zonary 4) incomplete zonary 5) discoid
cotyledonary classification?
noninvasive, chorionic villi restricted to specialized areas called cotyledons
cotyledon?
specialized areas on fetal placental membrane
caruncle?
maternal specialized regions on uterus to which the cotyledons attach
placentome?
cotyledon and caruncle together
Diffuse placental classification?
noninvasive, chrorionic villi distributed over entire surface of chorionic sac
Zonary placental classification?
invasive, chorionic villi restricted to an equitorial girdle around the placenta
Incomplete placental classification?
invasive, chorionic villi do not circumscribe placenta
Discoid placental classification?
invasive, chorionic villi arranged in a circular plate
Cow, sheep, deer have what type of placental classification?
cotyledonary
pig, horse, camel whale, dolphin have what placental classification?
diffuse
dog, cat, seal have what placental classification?
zonary
mink, bear, raccoon have what placental classification?
incomplete zonary
Primates, mouse, rat, rabbit, bat have what placental classification?
discoid
interstitial discoid?
invasion so deep that epithelium of endometrium grows back over invading placenta (in humans, chimps)
eccentric discoid?
bidiscoid, rhesus. secondary contact with uterine endometrium on side opposite of original implantation results in placental development on two sides of uterus
delayed implantation?
embryos of most species implant shortly after entering uterus but in a number of species implantation is delayed.
obligatory delayed implantation?
implantation delayed several months, may breed in fall and implant in spring; bats, bears, seals, armadillo, badger, weasel
embryonic diapause?
little embryonic growth
facultative delayed implantation?
induced by lactation and suckling; inhibits FSH and E2 secretions; may be induced by single injection E2 on a P4 background; E acts through ER and uterine metabolite catechol estrogens to activate embryo to implant
The blood gas exchange at the chorion is a __ attachment.
endometrium
The placenta is highly permeable to water and electrolytes stored in exchange between which two fluids?
allantoic and amniotic
The placenta coverts glucose to fructose which allows for storage in __ fluid.
allantoic
How is fetal fat formed?
from FA transferred across the placenta
How does the fetus make proteins?
from transferred amino acids
T/F: Fat soluble vitamins cross the placenta easier than the water soluble vitamins.
F
T/F: In domestic species, minerals are transferred across the placenta.
T
Antibodies to fight disease do/do not cross the placenta. Why or why not?
do not: the newborn will get these antibodies from the first milk (colostrum)
