Embryology 3 - The Early Fetal-Maternal Circulation (Week 8) Flashcards
REVIEW: The amniotic cavity is on the __________ (dorsal/ventral) surface of the developing embryo
dorsal
REVIEW: The umbilical vesicle is on the __________ (dorsal/ventral) surface of the developing embryo
ventral
REVIEW: The extraembryonic coelom that surrounds both the amniotic cavity and umbilical vesicle becomes the what?
chorionic cavity/sac
The chorion = ____________ on the inside + _____________ on the outside
extraembryonic somatic mesoderm,
trophoblastic cells
REVIEW: the trophoblasts consists of the ___________ and _____________
cytotrophoblast,
syncytiotrophoblast
REVIEW: The ______________ invades the endometrial stroma and helps induce apoptotic death of decidual cells
syncytiotrophoblast
_____________ release energy-rich glycogen and lipids that can freely diffuse to (and feed) the embryo
Decidual cells
REVIEW: What do the syncytioblasts release?
hCG
Note: this allows ovaries to continue to secrete high levels of progesterone, preventing endometrium shedding during menstruation
True or False: When the chorion and embryo have grown large enough and the distance becomes too far for the diffusion of nutrients between the endometrium and the embryo, the embryo must form its own circulation system. This happens around week 4.
True
The ___________ begins to form primary chorionic villi that project into the lacuna
Note: lacuna = “lakes of blood” from mom’s circulation
cytotrophoblast
When does the embryonic heart begin to beat?
~ day 21 (end of week 3)
What does the maternal-fetal circulation depend on?
1) a fetal cardiovascular system
2) structures within the endometrium that allow exchange with the fetal cardiovascular system
What are primary chorionic villi composed of?
cytotrophoblasts surrounded by a syncytiotrophoblastic shell
Note: ~ week 2
What are secondary chorionic villi composed of?
extraembryonic mesenchymal core surrounded by cytotrophoblast and syncytiotrophoblastic shell
Note: ~ week 3 (day 16)
What are tertiary chorionic villi composed of?
blood vessels (capillaries) within the mesenchymal core
- at this stage, fetal blood can now exchange substances (gas, nutrients, waste) between the maternal lacuna through the membrane formed by the tertiary villus
Note: ~ end of week 3 (day 21)
As villi develop, the cytotrophoblast pushes through the syncytiotrophoblast layer and forms the ______________, which anchors the chorionic sac and attaches it to the endometrium
cytotrophoblastic shell
a villus that attaches to the endometrium via cytotrophoblastic extensions
anchor villus
The ___________ is synonymous with the endometrium in a pregnant woman
decidua
What are the three separate areas of the decidua?
1) decidua basalis
2) decidua capsularis
3) decidua parietalis
the decidua that forms the placenta and is connected ot the embryo via the umbilical cord
decidua basalis
decidua that does not include the basalis, but is still associated with and covers the embryo
decidua capsularis
decidua formed by the endometrium that is NOT part of the embryo and is far from the site of implantation
decidua parietalis
True or False: As the embryo develops, the amniotic cavity gets bigger and bigger, and the chorionic cavity smaller and smaller.
True
Eventually our umbilical vesicle completely deteriorates and disappears
Maternal blood is found in the _____________
intervillous spaces
Note: maternal blood is “shot into” these spaces where it bathes the tertiary chorionic villi
Where do blood cells and blood vessels first develop?
extraembryonic tissue (umbilical vesicle and connecting stalk/chorion)
Note: begins in the 3rd week
the development of brand new blood vessels from the mesoderm
vasculogenesis
the “sprouting” of blood vessels formed by vasculogenesis (connecting blood vessels to each other)
angiogenesis
True or False: Angioblasts are derived from the mesoderm and are the cells that grow “blood islands”
True
As blood islands develop, they develop lumens which become what?
blood vessels
Angioblasts also give rise to early red blood cells within and outside the embryo. They are derived from where?
the inner lining of the new vessels (endothelium)
OUTSIDE EMBRYO: from the endothelium in allantois and the umbilical vesicle
INSIDE EMBRYO: from the endothelium of the dorsal aorta
True or False: Within the embryo, angioblastic chords form a pair of heart tubes that fuse at the end of the 3rd week to form the primordial heart tube (a single ventricle)
True
Cranial folding brings the heart tube __________ (ventrally/dorsally) and ____________ (cephalad/caudally)
ventrally and caudally
When do RBCs arise from the dorsal aorta?
~ week 5
The ___________ sends blood to the embryo and then to the umbilical artery (to tertiary villi), cardinal veins (to embryo), and the vitelline artery (to the umbilical vesicle)
dorsal aorta
The flow from dorsal aorta to cardinal veins feed the ____________ (intraembryonic/extraembryonic) tissues
intraembryonic
The ___________ returns blood from tertiary villi back to the embryonic heart
umbilical vein
By the end of the 4th week, the single “ventricle” rotates ____________ (clockwise/counterclockwise), such that the sinus venosus structures move to the right side of the heart and the atria posteriorly/superiorly
counterclockwise
