Implantation And Formation Of Placenta Flashcards
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Decidualization is under the influence of?
Progesterone and Oestrogen
After implantation, endometrial cells become larger and accumulate more nutritive substances. Which substances are these?
Glycogen, lipids, GAGs
What are the 3 regions of decidua
Basalis, capsularis and parietals
Decidua basalis?
Found between implanted blastocyst and myometrium
Decidua capsularis
Covers the implantation site and bulge of blastocyst, separates it from uterine cavity
Parietalis
The remainder of the uterine lining
What are the 3 stages of implantation
Apposition
Adhesion
Invasion
Where specifically is the site of implantation?
Usually body of uterus, upper part of posterior wall near the midline
Three things happen in the week of 2s. What are they?
Formation of bilaminar disc from embryoblast, epiblast and hypoblast
Formation of 2 cavities. Amniotic cavity related to epiblast and primary yolk sac related to hypoblast
Trophoblast differentiates into 2 layers. Cytotrophoblast(stem cell layer) and synctitiotrophoblast(functional layer)
When does extraembruonic mesoderm form and when?
At the end of the second week and in between the heuser membrane and inner cytotrophoblast
What is the chorion?
Trilaminar tissue consisting of outer synctiotrophoblast, middle cytotrophoblast and inner extraembryonic mesoderm
Primary yolk sac is also known as
Exoceolomic cavity
How is the chorionic cavity or extraembryonic coelom formed?
Formed by large cavities which develop in the extraembryonic mesoderm qnd become confluent. Surround primitive yolk sac and amniotic cavity except where germ disc is connected to the trophoblast by connecting stalk
Which space is encroached by enlarging amniotic cavity during lateral folding of the embryo
Extraembryonic coelom or chorionic cavity
What are the types of chorion
Frondosum - Rough chorion(which grows into the decidua basalis)
Laeve - Smooth chorion which grows into decidua capsularis
Note. By week 20, chorion leave and decidua capsularis come into complete contract with decidual oarietalis to form amniochorion
Which membrane ruptures during delivery of baby
Amniochorion
Fetal part of placenta develops form… and maternal part develops from.
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Chorionic sac(chorion frondosum) Endometrium(decidua basalis)
What makes chorion frondosum(rough chorion) appear rough
presence of finger like projections called chorionic villi
At first forms a sac which surrounds embryo/foetus
3 developmental types of chorionic villi
Primary
Secondary
tertiary
Structural types of chorionic villi
Stem : Attached to chorionic plate
Anchoring : Attached to nasal plate
Intermediate : branches from stem villi
Terminal or floating : blind ending no branches, site for feto maternal exchange
What is the placental barrier?
Structures across which other substances must diffuse from intervillous space to foetal capillary
6 layers in early placenta and 3 in late
Reduction achieved by syncytial knots(aggregate syncytial nuclei)
What are the 6 layers of early placenta
Synctiotrophoblast, cytotrophoblast, basement membrane of trophoblast, mesenchyme, basement membrane of villous(fetal capillary), fetal capillary endothelium
What are the 3 layers of late placenta
Synctiotrophoblast, fused foetal and villus basement membranes, and foetal capillary endothelium
Interchange occurs between foetal capillaries and chorionic vessels….
Foetal capillaries join to form chorionic vessels
Chorionic vessels join to form umbilical vessels
