Extraembryonic Membranes and Formation of Placental Complex Flashcards
what makes eem distinct
upon formation of 3 body folds (head, lateral, tail)
inner and outer layer of amnion
ecto (I) and eem (O)
inner and outer layer of chorion
eem (I) and ectoderm (O)
inner and outer layer of yolk sac
endoderm (I) and eem (O)
inner and outer layer of allantois
endoderm (I) and eem (O)
eem that are somatopleure in origin
amnion and chorion
eem that are splanchopleure in origin
yolk sac and allantois
development of chick embryo
oviparous
development of mammalian embryo
viviparous
how does placenta form
as chorionic villi > invade endometrium > breakdown maternal BVs > exchange and absorption of materials
what makes up the umbilical cord
connecting stalk, yolk stalk > housed by amnion
what separates ICM and trophoblast
amniotic cavity
yolk sac and function
1st to appear, grows over yolk mass
functions: makes yolk soluble materials, cell lining of endometrium bvs, hematopoiesis, PGCs
amnion and function
encloses amniotic cavity
protects embryo from adhesions and mechanical stress
chorion and function
chick: transport shell to embryo circulation > beak and skeleton & exchange of respi gases
mammals: respiration, filtration, HORMONE PRODUCTION
allantois and function
ventral wall of hindgutt
mesoderm fused with chorion (forming chorioallantoic membrane) and amnion
function: wastes and gas exchange
c - nitrogenous wastes
m - vascular network of placenta
function of chorioallantoic membrane
efficient respiratory structure
explain how yolk sac is formed
layer of mesodermal cells around edges of blastocyst > forms complete pouch (visible after 10d fertilization)
explain how amnion is formed
cells from blastodisc > migrates around a cavity separating ICM and trophoblast (amniotic cavity) and away from disc, moving between ectodermal lining of amniotic cavity
what forms the large part of the placenta
amnionic ectoderm, extraembryonic endoderm, yolk sac, extraembryonic mesoderm
explain formation of allantois
begins as outpocketing of the endoderm (hindgut) > tip grows toward the wall of blastocyst > surrounded by mesodermal cells
explain formation of chorion
mesoderm associated with allantois spread around blastocyst > mesoderm and trophoblast combination
what houses the blood vessels and allantois
chorionic and connecting stalk
this is the combination of the extraembryonic membrane and lining of the uterus;
the site of physiological exchange between mother and embryo
placenta
furnished by extraembryonic membranes
fetal tissue
furnished by uterine endometrium
maternal tissue
fetal tissue is largely contributed by what extraembryonic membrane?
chorion
what are the types of placenta based on the degree of contact of placental components?
deciduous: villi are embedded, shedding and bleeding occurs, intimate contact
non-deciduous: NO shedding and bleeding, villi NOT embedded, loose contact
type of placenta wherein the villi are spread our and greater part of chorion surface is associated with endometrium
- example
diffused placenta
ex: pig
type of placenta wherein the contact is restricted to the localized patches of villi
- example of animal
cotyledonary
ex:sheep, cow, deer
type of placenta wherein the contact involved girdlike band encircling the blastocyst; villi are arranged in transverse zones and penetrate uterine wall
- example
zonary placenta
- carnivores, cats, dogs
type of placenta wherein the contact is restricted to a disc or plate; villi form a disc that is intimately connected to the uterine wall
- example
discoidal placenta
- humans, rodents, rabbits
type of placenta with only 4 tissue layers
endotheliochorial
type of placenta with only 3 tissue layers
hemochorial
type of placenta with 6 tissue layers
epitheliochorial