Cleavage Stages and Placental Development Flashcards
Where does fertilization usually occur?
Ampulla
Events of fertilization
- Corona radiata
- Zona pellucida
- Zona reaction
Corona radiata
layer of cuboidal cells surrounding the egg; sperm enter by secreting proteolytic enzymes
Zona pellucida and cortical reaction
- layer of glycoproteins; acrosome reaction happens where acrosome (cap) over the head of the sperm ruptures and releases digestive enzymes that degrade the glycoproteins
- When the first sperm penetrates, cortical granules lining the ovum membrane rupture, releasing enzymes like peroxidases (cortical reaction)
Zona reaction
release of enzymes in cortical reaction inactivate receptors for spermatozoa binding on the outside of the zone, preventing further sperm from penetrating
Sperm nucleus enters egg cytoplasm and becomes…
male pronucleus
Once male pronucleus forms, the egg is now ________ and is called a _______.
fertilized; zygote
Once female pronucleus develops, pronuclei drawn together during….via….and then they….
first mitotic division via mitotic spindle; membranes break down and intermix
Cells of early embryo…
Blastomeres
After 3rd cleavage, 8 cell embryo is called…
Morula
Compaction
Separation of inner (fetus) and outer (chorion and placenta) cells
After organization of ICM, trophoblast, and blastocoel, embryo known as…
Blastocyst
ICM produces…
Fetus, yolk sac, and extraembyonic mesoderm
Outer mass fate…
trophoblast
Trophoblast produces….
extraembyonic layers (cytotrophoblast, synctiotrophoblast)
Hatching
Blastocyst prepares for implantation by hatching from zona pellucida
Morphogenesis of embryonic circulatory system
a. Mesenchymal cells differentiate into angioblasts > primitive RBCs OR endothelial cells to produce capillaries > interconnect to establish embryonic circulatory system
Primary villi
cytotrophoblast core surrounded by synctiotrophoblast
Secondary villi
Mesodermal core develops w/i cytotrophoblast
Tertiary villi
Blood vessels invade mesoderm
Once villi invade all the way to endometrium, they form a layer called…
Outer trophoblast shell
Terminal villi
Branch off of stem villi
Nutrient exchange b/w fetal and maternal circulation through…
Terminal tertiary villi
Maternal component of placenta begins with…
Trophoblastic lacunae forming in the synctiotrophoblast
Maternal sinusoids
Expanded trophoblastic lacunae that have coalesced with glands and capillaries in overlying endometrium
Overlying endometrium known as…
Decidua
Where does maternal blood flow?
Intervillous space
Where does embryonic blood flow?
Within vessels in villi
