Maternal Recognition of Pregnancy Flashcards
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continuation of cyclicity occurs due to
luteolysis
the maternal recognition of pregnancy is defined as
Series of events where conceptus
signals its presence
Prevents luteolysis (saves corpus luteum) so progesterone can establish
pregnancy
pregancy recognition factors in rodents
prolactin
pregnancy recognition factors in ruminants
interferon τ, aka (IFN τ)
pregnancy recognition factors in pigs
estrogen
in bitch and queen
no anti-luteolytic signal (or pregnancy signal)
IFNT -τ
Anti-luteolytic hormone for pregnancy recognition and CL maintenance, silences expression of
estrogen receptors which:
blocks OXT-induced release of
luteolytic pulses of PGF2α,
preventing CL regression
Name the stages of transuterine migration of the equine conceptus
1) Embryo mobility
2) Inhibition of luteolysis
3) Embryo fixation
4) Orientation
embryo mobility in equines is facilitated by
prostaglandins inducing uterine contractions either at the conceptus or origin of uterus
Function of the Equine Embryonic Capsule
becomes the outermost layer after the shedding of the zona pellucida to become a supportive wrapping of the embryo while it experiences mobility, fixation and orientation
Maternal Recognition of Pregnancy in Pigs
Estrogen produces anti-luteolytic effect that directs PGF2a into the uterine lumen where it is metabolized
prolactin and Ca2+ also involved
define embryo implantation
Process by which the embryo attaches to the endometrium of the uterus
types of implantation are classified by
the extent of blastocyst penetration into the uterine wall at the invasion stage
Non-invasive implantation
- superficial
- blastocyst expands to fill the lumen of the uterus/uterine horn
- blastocyst doesn’t erode, instead grows large enough to fully contact the surface of the lumen in order to fuse to it without penetration
non-invasive implantation occurs in what species?
horses, cattle, sheep, pigs, dogs, cats
types of invasive implantation
interstitial vs. eccentric
Interstitial implantation
the blastocyst remains small and fully embeds into the uterine wall (primates)
Eccentric Implantation
the bastocyst remains small and **only partially **embeds into the uterine wall (rodents)
name the phases of embryo implantation
- apposition
- attachment/adhesion
- invasion
what occurs during apposition?
the hatched blastocyst establishes it’s contact with the endometrium
what occurs during attachment/adhesion?
the association between the trophoblast and epithelium strengthens through the interaction of adhesion molecules
What occurs during invasion?
human trophoblast invades tissue and secures blood supply
non-invasive embryo implantation occurs in
domestic animals
(apposition to adhesion)
invasive embryo implantation occurs in
primates
apposition –> adhesion –> invasion
steps of non-invasive implantation
Implantation of blastocysts for ruminants and pigs includes:
1) Hatching from zona pellucida
2) Precontact and orientation of the blastocyst with uterine luminal epithelium (LE)
3) Apposition between conceptus trophectoderm and uterine LE
4) Adhesion of conceptus trophectoderm to uterine LE
5) No endometrial invasion by the conceptus
steps of invasive implantation
Zona Hatching: early bastocyst hatches from zona pellucida
Apposition: blastocyst establishes contact with endometrium
Adhesion/Attachment: increased communication between embryo and endometrium (autocrine/paracrine secretion)
**Invasion: **blastocyst invades and buries into uterine to reach blood supply
Syncytiotrophoblast
- the outer layer that covers the interface between the embryo and the maternal blood vessels
- produces human chorionic gonadotropin (hCG) which rescues the corpus luteum
Cytotrophoblast
a single sheet of cells surrounding the extraembryonic mesoderm
Gastrulation
Formation of germ layers – ectoderm, mesoderm, and endoderm
embryonic folding
- folding of flat trilaminar disc into cylindrical embryo
- occurs in median and horizontal planes, due to rapid embryo growth
- Endodermal, mesodermal, and ectodermal layers of the embryonic disc fuse to the corresponding layer on the opposite side, creating a 3-D tubular form
- Separates embryo from its extraembryonic membranes
organogenesis
The formation of organ rudiments and organ systems
Steps of Embryo and Fetal Development
1) Gastrulation
2) Formation of tube-within-a-tube body plan (germ layers)
3) organogenesis
formation of germ layers
Bilaminar disc – Epiblast and Hypoblast; Trilaminar disc – Endoderm, Mesoderm and Ectoderm
germ layer derivates
Endoderm: digestive system, lungs, endocrine
Mesoderm: muscle, skeleton, cardiovascular, reproductive
Ectoderm: nervous system, skin, hair
define embryo
organism in early stages of development
conceptus
product of conception
conceptus includes
- embryo during early embryonic stage
- embryo and extraembryonic membranes during preimplantation stage
- fetucs and placenta during post-attachment phase
